opportunity during ten years to help my University in the acquisition
and arrangement of the finest collection of remains of these animals in
Europe. Out of an area of a few acres, during a year or two, came the
thousand bones of Ornithosaurs, mostly associated sets of remains, each
a part of a separate skeleton, described in my published catalogues, as
well as the best of those at York and in the British Museum and other
collections in London.

The deposit which yields them, named Cambridge Greensand, may or may not
represent a long period of time in its single foot of thickness; but the
abundance of fossils, obtained whenever the workmen were adequately
remunerated for preserving them, would suggest that the Pterodactyles
might have lived like sea-birds or in colonies like the Penguins, if it
were not that the number of examples of each species found is always
small, and the many variations of structure suggested rather that the
individuals represent the life of many lands. The collections of remains
are mostly from villages in the immediate vicinity of Cambridge, such as
Chesterton, Huntingdon Road, Coldham Common, Haslingfield, Barton,
Shillington, Ditton, Granchester, Harston, Barrington, stretching south
to Ashwell in Bedfordshire on the one hand, as well as further north by
Horningsea into the fens. Each appears to be the associated bones of a
single individual. The remains mostly belong to comparatively large
animals. Some were small, though none have been found so diminutive as
the smallest from the Solenhofen Slate. The largest specimens with long
jaws appear to have had the head measuring not more than eighteen inches
in length, which is less than half the size of the great toothless
Pterodactyles from Kansas.

  [Illustration: FIG. 69.  RESTORATION OF THE SKULL OF ORNITHOCHEIRUS

  The parts left white are in the Geological Museum at Cambridge. The
  shaded parts have not been found. The two holes are the eye and the
  nostril (From the Cambridge Greensand)]

The Cambridge specimens manifestly belong to at least three genera.
Something may be said of the characters of the large animals which are
included in the genus Ornithocheirus. These fossils have many points of
structure in common with the great American toothless forms which are of
similar geological age. The skull is remarkable for having the back of
the head prolonged in a compressed median crest, which rose above the
brain case, and extended upward and over the neck vertebræ, so as to
indicate a muscular power not otherwise shown in the group. For about
three inches behind the brain this wedge of bone rested on the vertebræ,
and probably overlapped the first three neural arches in the neck.

Another feature of some interest is the expansion of the bone which
comes below the eye. In Birds this malar or cheek bone is a slender rod,
but in these Pterodactyles it is a vertical plate, which is blended with
the bone named the quadrate bone, which makes the articulation with the
lower jaw in all oviparous animals.

The beak varies greatly in length and in form, though it is never quite
so pointed as in the American genus, for there is always a little
truncation in front, when teeth are seen projecting forward from a
position somewhat above the palate; the snout is often massive and
sometimes club-shaped. Except for these variations of shape in the
compressed snout, which is characterised by a ridge in the middle of the
palate, and a corresponding groove in the lower jaw, and the teeth,
there is little to distinguish what is known of the skull in its largest
English Greensand fossils from the skull remains which abound in the
Chalk of Kansas.

This English genus Ornithocheirus, represented by a great number of
species, had the neural arch of the neck bones expanded transversely
over the body of the vertebra in a way that characterises many birds
with powerful necks, and is seen in a few Pterodactyles from Solenhofen.

It is difficult to resist the conclusion that the neck vertebræ were
not usually more than twice to three times as long as those of the back,
and it would appear that the caudal vertebræ in the English Cretaceous
types were comparatively large, and about twice as long as the dorsal
vertebræ. Unless there has been a singular succession of accidents in
the association of these vertebræ with the other remains, Ornithocheirus
had a tail of moderate length, formed of a few vertebræ as long as those
of the neck, though more slender, quite unlike the tail in either the
long-tailed or short-tailed groups of Solenhofen Pterodactyles, and
longer than in the toothless Pterodactyles of America.

  [Illustration: FIG. 70.  CERVICAL VERTEBRA, ORNITHOCHEIRUS

  Under side, half natural size. (Cambridge Greensand)]

The singular articulation for the humerus at the truncated extremity of
the coracoid bone is a character of this group, as is the articulation
of the scapulæ with the neural arches of the dorsal vertebræ, at right
angles to them (p. 115), instead of running over the ribs as in Birds
and as in other Pterodactyles.

The smaller Pterodactyles have their jaws less compressed from side to
side. The upper arm bone, the humerus, instead of being truncated at its
lower end as in Ornithocheirus, is divided into two or three rounded
articular surfaces. That for the radius, the bone which carries the
wrist, is a distinct and oblique rounded facet, while the ulna has a
rounded and pulley-like articulation on which the hand may rotate. These
differences are probably associated with an absence of the remarkable
mode of union of the scapulæ with the dorsal vertebræ. But I have
hesitated to give different names to these smaller genera because no
example of scapula has come under my notice which is not truncated at
the free end. I do not think this European type can be the Nyctodactylus
of Professor Marsh, in which sutures appear to be persistent between the
bodies of the vertebræ and their arches, because no examples have been
found at Cambridge with the neural arches separated, although the
scapula is frequently separated from the coracoid in large animals.

  [Illustration: FIG. 71.  UPPER AND LOWER JAWS OF AN ENGLISH
  PTERODACTYLE FROM THE CHALK, AS PRESERVED]

ORNITHOSTOMA

  [Illustration: FIG. 72.  THE PALATE OF THE ENGLISH TOOTHLESS
  PTERODACTYLE, ORNITHOSTOMA]

  [Illustration: FIG. 73.  TYPES OF THE AMERICAN TOOTHLESS PTERODACTYLE,
  ORNITHOSTOMA

  Named by Marsh, Pteranodon]

The most interesting of all the English Pterodactyle remains is the
small fragment of jaw figured by Sir Richard Owen in 1859, which is a
little more than two inches long and an inch wide, distinguished by a
concave palate with smooth rounded margins to the jaws and a rounded
ridge to the beak. It is the only satisfactory fragment of the animal
which has been figured, and indicates a genus of toothless
Pterodactyles, for which the name Ornithostoma was first used in 1871.
After some years Professor Marsh found toothless Pterodactyles in
Kansas, and indicated several species. There are remains to the number
of six hundred specimens of these American animals in the Yale Museum
alone; but very little was known of them till Professor Williston, of
Lawrence, in Kansas, described the specimens from the Kansas University
Museum, when it became evident that the bones of the skeleton are mostly
formed on the same plan as those of the Cambridge Greensand genus,
Ornithocheirus. They are not quite identical. Professor Williston adopts
for them the name Ornithostoma, in preference to Pteranodon which Marsh
had suggested. Both animals have the dagger-shaped form of jaw, with
corresponding height and breadth of the palate. The same flattened sides
to the snout, converging upwards to a rounded ridge, the same compressed
rounded margin to the jaw, which represents the border in which teeth
are usually implanted, and in both the palate has the same smooth
character forming a single wide concave channel. Years previously I had
the pleasure of showing to Professor Marsh the remarkable characters of
the jaw, shoulder-girdle bones, and scapulæ in the Greensand
Pterodactyles while the American fossils were still undiscovered. I
subsequently made the restoration of the shoulder-girdle (p. 115).
Professor Williston states to me that the shoulder-girdle bones in
American examples of Ornithostoma have a close resemblance to those of
Ornithocheirus figured in 1891, as is evident from remains now shown in
the British Museum. It appears that the Kansas bones are almost
invariably crushed flat, so that their articular ends are distorted. The
neck vertebræ are relatively stout as in Ornithocheirus. The hip-girdle
of the American Ornithostoma can be closely paralleled in some English
specimens of Ornithocheirus, though each prepubic bone is triangular in
the American fossils as in _P. rhamphastinus_. They are united into a
transverse bar as in Rhamphorhynchus, unknown in the English fossils.
The femur has the same shape as in Ornithocheirus; and the long tibia
terminates in a pulley. There is no fibula. The sternum in both has a
manubrium, or thick keel mass, prolonged in front of its articular
facets for the coracoid bones, which are well separated from each other.
Four ribs articulate with its straight sides. The animal has four toes
and the fifth is rudimentary; there are no claws to the first and
second.

  [Illustration: FIG. 74.  RESTORATION OF THE SKELETON OF _ORNITHOSTOMA
  INGENS_ (MARSH)

  From the Niobrara Cretaceous of Western Kansas. Made by Professor
  Williston. The original has a spread of wing of about 19 feet 4
  inches. Fragments of larger individuals are preserved at Munich]

In the restoration which Professor Williston has made the wing
metacarpal is long, and in the shortest specimen measures 1 foot 7
inches, and in the longest 1 foot 8 inches. This is exactly equal to the
length of the first phalange of the wing finger. The second wing finger
bone is 3 inches shorter, the third is little more than half the length
of the first, while the fourth is only 6-3/4 inches long, showing a
rapid shortening of the bones, a condition which may have characterised
all the Cretaceous Pterodactyles. The short humerus, about 1 foot long,
and the fore-arm, which is scarcely longer, are also characteristic
proportions of Ornithostoma or Pteranodon, as known from the American
specimens. Professor Williston gives no details of the remarkable tail,
beyond saying that the tail is small and short, and that the vertebræ
are flat at the ends, without transverse processes. In the restoration
the tail is shorter than in the short-tailed species from the
Lithographic Slate, and unlike the tail in Ornithocheirus.

This is the succession of Pterodactyles in geological time. Their
history is like that of the human race. In the most ancient nations
man's life comes upon us already fully organised. The Pterodactyles
begin, so far as isolated bones are concerned, in the Rhætic strata;
perhaps in the Muschelkalk or middle division of the Trias. And from the
beginning of the Secondary time they live on with but little diversity
in important and characteristic structures, and so far as habit goes,
the great Pterodactyles of the Upper Chalk of England cannot be said to
be more highly organised than the earlier stiff-tailed genera of the
Lias or the Oolites. There is nothing like evolution. No modification
such as that which derives the one-toed horse or the two-toed ox from
ancestors with a larger number of digits. On the other hand, there is
little, if any, evidence of degeneration. The later Pterodactyles do not
appear to have lost much, although the tail in some of the Solenhofen
genera may be degenerate when compared with the long tail of
Dimorphodon; but the short-tailed types are found side by side with the
long-tailed Rhamphorhynchus. The absence of teeth may be regarded as
degeneration, for they have presumably become lost, in the same way that
Birds now existing have lost the teeth which characterised the fossil
birds--Ichthyornis of the American Greensand, and Archæopteryx of the
Upper Oolites of Bavaria. But just as some of the earlier Pterodactyles
have no teeth at the extremity of the jaw, such as Dorygnathus and
Rhamphorhynchus, so the loss of teeth may have extended backward till
the jaws became toothless. The specimens hitherto known give no evidence
of such a change being in progress. But just as the division of Mammals
termed Edentata usually wants only the teeth which characterise the
front of the jaw, yet others, like the Great Ant-eater of South America
named Myrmecophaga, have the jaws as free from teeth as the toothless
Pterodactyles or living Birds, and show that in that order the teeth
have no value in separating these animals into subordinate groups any
more than they have among the Monotremata, where one type has teeth and
the other is toothless.

The following table gives a summary of the Geological History and
succession in the Secondary Rocks of the principal genera of Flying
Reptiles.

  -----------------------+----------------------------------------------
                         |             NAMES OF THE GENERA.
  GEOLOGICAL FORMATIONS. +-----------------------+----------------------
                         | British and European. | North American.
  -----------------------+-----------------------+----------------------
  Upper Chalk            |                       |} Ornithostoma
                         |                       |}     (_Pteranodon_)
  Lower Chalk            |} Ornithocheirus       |} Nyctodactylus
  Upper Greensand        |}   |  Ornithostoma    |
  Gault                  |    |                  |
  -----------------------+    |                  |
  Lower Greensand        |    |                  |
  Wealden                | Ornithodesmus         |
  Purbeck                | Doratorhynchus        |
  -----------------------+                       |
  Portland               |{ Pterodactylus        |
                         |{ Ptenodracon          |
  Kimeridge Clay and     |{ Cycnorhamphus        |
    Solenhofen Slate     |{ Diopecephalus        |
                         |{ Rhamphorhynchus      |
  Coralline Oolite       |{ Scaphognathus        |
                         |                       |
  Oxford Clay            |                       |
  -----------------------+                       |
  Great Oolite and       |                       |
    Stonesfield Slate    | Rhamphocephalus       |
                         |                       |
  Inferior Oolite        |                       |
  -----------------------+                       |
  Upper Lias             |{ Campylognathus       |
                         |{ Dorygnathus          |
  Lower Lias             |  Dimorphodon          |
  -----------------------+                       |
  Rhætic                 |  bones                |
                         |                       |
  Muschelkalk            |  ? bones              |
  -----------------------+-----------------------+----------------------

CHAPTER XVI

CLASSIFICATION OF THE ORNITHOSAURIA

When an attempt is made to determine the place in nature of an extinct
group of animals and the relation to each other of the different types
included within its limits, so as to express those facts in a
classification, attention is directed in the first place to characters
which are constant, and persist through the whole of its constituent
genera. We endeavour to find the structural parts of the skeleton which
are not affected by variation in the dentition, or the proportions of
the extremities, or length of the tail, which may define families or
genera, or species.

It has already been shown that while in many ways the Ornithosaurian
animals are like Birds, they have also important resemblances to
Reptiles. They are often named Pterosauria. The wing finger gives a
distinctive character which is found in neither one class of existing
animals nor the other, and is common to all the Pterodactyles at present
known. They have been named Ornithosauria as a distinct minor division
of back-boned animals, which may be regarded as neither Reptiles nor
Birds in the sense in which those terms are used to define a Lizard or
Ostrich among animals which still exist. It is not so much that they
mark a transition from Reptile to Bird, as that they are a group which
is parallel to Birds, and more manifestly holds an intermediate place
than Birds do between Reptiles and Mammals. In plan of structure Bird
and Reptile have more in common than was at one time suspected. The late
Professor Huxley went so far as to generalise on those coincidences in
parts of the skeleton, and united Birds and Reptiles into one group,
which he named Sauropsida, to express the coincidences of structure
between the Lizard and the Bird tribes. The idea is of more value than
the term in which it is expressed, because Reptiles are not, as we have
seen, a group of animals which can be defined by any set of characters
as comprehensive as those which express the distinctive features of
Birds. From the anatomist's point of view Birds are a smaller group, and
while some Reptiles have affinity with them, it is rather the extinct
than the living groups which indicate that relation. Other Reptiles have
affinities of a more marked kind with Mammals, and there are points in
the Ornithosaurian skeleton which are distinctly Mammalian. So that when
the Monotreme Mammals are united with South African reptiles known as
Theriodontia, which resemble them, in a group termed Theropsida to
express their mammalian resemblances, it is evident that there is no one
continuous chain of life or gradation in complexity of structure of
animals.

We have to determine whether the Ornithosauria incline towards the
Sauropsidan or Bird-Reptile alliance, or to the Mammal-Reptile or
Theropsidan alliance. There can be no doubt that the predominant
tendency is to the former, with a minor affinity towards the latter.

The Ornithosauria are one of a series of groups of animals, living and
extinct, which have been combined in an alliance named the
Ornithomorpha. That group includes at least five great divisions of
animals, which circle about birds, known as Ornithosauria, Crocodilia,
Saurischia, Aves, Ornithischia, and Aristosuchia. Their relations to
each other are not evident in an enumeration, but may be shown in some
degree in a diagram (see p. 190).

THE ORNITHOMORPHA

The Ornithomorpha arranged in this way show that the three middle
groups--carnivorous Saurischia, Aristosuchia, herbivorous
Ornithischia--which are usually united as Dinosauria, intervene between
Birds and Ornithosaurs; and that the Crocodilia and Ornithosauria are
parallel groups which are connected with Birds, by the group of
Dinosaurs, which resembles Birds most closely.

The Ornithomorpha is only one of a series of large natural groups of
animals into which living and extinct terrestrial vertebrata may be
arranged. And the succeeding diagram may contribute to make evident the
relations of Ornithosauria to the other terrestrial vertebrata (see p.
191).

Herein it is seen that while the Ornithomorpha approach towards Mammalia
through the Ornithosauria, and less distinctly through the Crocodilia,
they approach more directly to the Sauromorpha, through the Plesiosaurs
and Hatteria; while that group also approaches more directly to the
Mammals through the Plesiosaurs and Anomodonts.

  [Illustration: DIAGRAM OF THE AFFINITIES OF THE ORDERS OF ANIMALS
  COMPRISED IN THE ORNITHOMORPHA.

  After a diagram in the _Philosophical Transactions of the Royal
  Society_, 1892.]

The Aristosuchia is imperfectly known, and therefore to some extent a
provisional group. It is a small group of animals.

  [Illustration: DIAGRAM SHOWING THE RELATIONS OF THE ORNITHOMORPHA
  TO THE CHIEF LARGE GROUPS OF TERRESTRIAL VERTEBRATA, AND THEIR
  AFFINITIES WITH EACH OTHER.

  After a diagram in the _Philosophical Transactions of the Royal
  Society_, 1892.]

Cordylomorpha are Ichthyosaurs and the Labyrinthodont group.
Herpetomorpha include Lacertilia, Homoeosauria, Dolichosauria,
Chameleonoidea, Ophidia, Pythonomorpha.

The Sauromorpha comprises the groups of extinct and living Reptiles
named Chelonia, Rhynchocephala, Sauropterygia, Anomodontia, Nothosauria,
and Protorosauria. These details may help to explain the place which has
been given to the Ornithosauria in the classification of animals.

  [Illustration: FIG. 75.  COMPARISON OF SIX GENERA

  The skulls are seen on the left side in the order of the names below
  them]

Turning to the Pterodactyles themselves, Von Meyer divided them
naturally into short-tailed and long-tailed. The short-tailed indicated
by the name Pterodactylus he further divided into long-nosed and
short-nosed. The short-nosed genus has since been named Ptenodracon
(Fig. 59, p. 167). The long-tailed group was divided into two types--the
Rhamphorhynchus of the Solenhofen Slate (Fig. 56, p. 161) and the
English form now known as Dimorphodon (Fig. 52, p. 150), which had been
described from the Lias.

The Cretaceous Pterodactyles form a distinct family. So that, believing
the tail to have been short in that group (Fig. 58), there are two
long-tailed as well as two short-tailed families, which were defined
from their typical genera Pterodactylus, Ornithocheirus,
Rhamphorhynchus, and Dimorphodon.

The differences in structure which these animals present are, first: the
big-headed forms from the Lias like Dimorphodon, agree with the
Rhamphorhynchus type from Solenhofen in having a vacuity in the skull
defined by bone, placed between the orbit of the eye and the nostril.
With those characters are correlated the comparatively short bones which
correspond to the back of the hand termed metacarpals, and the tail is
long, and stiffened down its length with ossified tendons. These
characters separate Ornithosaurs with long tails from those with short
tails.

The short-tailed types represented by Pterodactylus and Ornithocheirus
have no distinct antorbital vacuity in the skull defined by bone. The
metacarpal bones of the middle hand are exceptionally elongated, and the
tail, which was flexible in both, appears to have been short. These
differences in the skeleton warrant a primary division of flying
reptiles into two principal groups.

The short-tailed group, which was recognised by De Blainville as
intermediate between Birds and Reptiles, may take the name
Pterodactylia, which he suggested as a convenient, distinctive name. It
may probably be inconvenient to enlarge its significance to comprise not
only the true Pterodactyles originally defined as Pterosauria, but the
newer Ornithostoma and Ornithocheirus which have been grouped as
Ornithocheiroidea.

The second order, in which the wing membrane appears to have had a much
greater extent, in being carried down the hind limbs, where the
outermost digit and metatarsal are modified for its support, has been
named Pterodermata, to include the types which are arranged around
Rhamphorhynchus and Dimorphodon.

Both these principal groups admit of subdivision by many characters in
the skeleton, the most remarkable of which is afforded by the pair of
bones carried in front of the pubes, and termed prepubic bones. In the
Pterodactyle family the bones in front of the pubes are always separate
from each other, always directed forward, and have a peculiar fan-shaped
form with concave sides like the bone which holds a similar position in
a Crocodile. In the Ornithocheirus family the prepubic bones appear to
have been originally triangular, but were afterwards united so as to
form a strong continuous bar which extends transversely across the
abdomen in advance of the pubic bones. This at least is the distinctive
character in the genus Ornithostoma according to Professor Williston,
which in many ways closely resembles Ornithocheirus.

The two families in the long-tailed order named Pterodermata are
separated from each other by a similar difference in their prepubic
bones. In Dimorphodon those bones are separate from each other, and
remain distinct through life, meeting in the middle line of the body in
a wide plate. On the other hand, in Rhamphorhynchus the prepubic bones,
which are at first triangular and always slender, become blended
together into a slight transverse bar, which only differs from that
attributed to Ornithostoma in its more slender bow-shaped form.

  [Illustration: FIG. 76.  LEFT SIDE OF PELVIS OF ORNITHOSTOMA
  (After Williston)]

Thus if other characters of the skeleton are ignored and a
classification based upon the structure of the pelvis and prepubic
bones, there would be some ground for associating the long-tailed
Rhamphorhynchus from the Upper Oolites which is losing the teeth in the
front of its jaw with the Cretaceous Ornithostoma, which has the teeth
completely wanting; while the long-tailed Dimorphodon would come into
closer association with the short-tailed Pterodactylus. The drum-stick
bone or tibia in Dimorphodon, with its slender fibula, like that of a
Bird, also resembles a Bird in the rounded and pulley-shaped terminal
end which makes the joint corresponding to the middle of the ankle bones
in man. The same condition of a terminal pulley joint is found in the
Cretaceous Pterodactyles. But in the true Pterodactyles and in
Rhamphorhynchus there usually is no pulley-shaped termination to the
lower end of the drum-stick, for the tarsal bones remain separate from
each other, and form two rows of ossifications, showing the same
differences as separate Dinosaurs into the divisions which have been
referred to, from their Bird-like pelvis and tibio-tarsus, as
Ornithischia in the one case, and Saurischia in the other from their
bones being more like those of living Lizards.

CHAPTER XVII

FAMILY RELATIONS OF PTERODACTYLES TO ANIMALS WHICH LIVED WITH THEM

Enough has been said of the general structure of Pterodactyles and the
chief forms which they assumed while the Secondary rocks were
accumulating, to convey a clear idea of their relations to the types of
vertebrate animals which still survive on the earth. We may be unable to
explain the reasons for their existence, and for their departure from
the plan of organisation of Reptiles and Birds. But the evidence has not
been exhausted which may elucidate their existence. Sometimes, in
problems of this kind, which involve comparison of the details of the
skeleton in different animals, it is convenient to imagine the
possibility of changes and transitions which are not yet supported by
the discovery of fossil remains. If, for example, the Pterodactyle be
conceived of as divested of the wing finger, which is its most
distinctive character, or that finger is supposed to be replaced by an
ordinary digit, like the three-clawed digits of the hand which we have
regarded as applied to the ground, where, it may be asked, would the
animal type be found which approximates most closely to a Pterodactyle
which had been thus modified? There are two possible replies to such a
question, suggested by the form of the foot. For the old Bird
Archæopteryx has three such clawed digits, but no wing finger. And some
Dinosaurs also have the hand with three digits terminating in claws,
which are quite comparable to the clawed digits of Pterodactyles.

The truth expressed in the saying that no man by taking thought can add
a cubit to his stature is of universal application in the animal world,
in relation to the result upon the skeleton of the exercise of a
function by the individual. Yet such is the relation in proportions of
the different parts of the animal to the work which it performs, so
marked is the evidence that growth has extended in direct relation to
use of organs and active life, and that structures have become dwarfed
from overwork, or have wasted away from disuse--seen throughout all
vertebrate animals, that we may fairly attribute to the wing finger some
correlated influence upon the proportions of the animal, as a
consequence of the dependence of the entire economy upon each of its
parts. Therefore if an allied animal did not possess a wing finger, and
did not fly, it might not have developed the lightness of bone, or the
length of limb which Pterodactyles possess.

The mere expansion of the parachute membrane seen in so-called flying
animals, both Mammals and Reptiles, which are devoid of wings, is
absolutely without effect in modifying the skeleton. But when in the Bat
a wing structure is met with which may be compared to a gigantic
extension of the web foot of the so-called Flying Frog, the bones of the
fingers and the back of the hand elongate and extend under the stimulus
of the function of flight in the same way as the legs elongate in the
more active hoofed animals, with the function of running. Therefore it
is not improbable that the limbs shared to some extent in growth under
stimulus of exercise which developed the wing finger. And if an animal
can be found among fossils so far allied as to indicate a possible
representative of the race from which these Flying Dragons arose, it
might be expected to be at least shorter legged, and possibly more
distinctly Reptilian in the bones of the shoulder-girdle which support
the muscles used in flight. It may readily be understood that the kinds
of life which were most nearly allied to Pterodactyles are likely to
have existed upon the earth with them, and that flight was only one of
the modes of progression which became developed in relation to their
conditions of existence. The principal assemblage of terrestrial animals
available for such comparison is the Dinosauria. They may differ from
Pterodactyles as widely as the Insectivora among Mammals differ from
Bats, but not in a more marked way. Comparisons will show that there are
resemblances between the two extinct groups which appeal to both reason
and imagination.

Dinosaurs are conveniently divided by characters of the pelvis first
into the order Saurischia, which includes the carnivorous Megalosaurus
and the Cetiosaurus, with the pelvis on the Reptile plan; and secondly
the order Ornithischia, represented by Iguanodon, with the pelvis on the
Bird plan. It may be only a coincidence, but nevertheless an interesting
one, that the characters of those two great groups of reptiles, which
also extend throughout the Secondary rocks, are to some extent
paralleled in parts of the skeleton of the two divisions of
Pterodactyles. This may be illustrated by reference to the skull,
pelvis, hind limb, and the pneumatic condition of the bones.

  [Illustration: FIG. 77.  COMPARISON OF THE SKULL OF THE DINOSAUR
  ANCHISAURUS WITH THE ORNITHOSAUR DIMORPHODON]

The Saurischian Dinosauria have an antorbital vacuity in the side of the
skull between the nasal opening and the eye, as in the long-tailed
Ornithosaurs named Pterodermata. In some of the older genera of these
carnivorous Dinosaurs of the Trias, the lateral vacuities of the head
are as large as in Dimorphodon. But in some at least of the Iguanodont,
or Ornithischian Dinosaurs, there is no antorbital vacuity, and the side
of the face in that respect resembles the short-tailed Pterodactylia.
The skull of a carnivorous Dinosaur possesses teeth which, though easily
distinguished from those of Pterodactyles, can be best compared with
them. The most striking difference is in the fact that in the Dinosaur
the nostrils are nearly terminal, while in the Pterodactyle they are
removed some distance backward. This result is brought about by growth
taking place, in the one case at the front margin of the maxillary bone
so as to carry the nostril forward, and in the other case at the back
margin of the premaxillary bone. Thus an elongated part of the jaw is
extended in front of the nostril. Hence there is a different proportion
between the premaxillary and maxillary bones in the two groups of
animals, which corresponds to the presence of a beak in a bird, and its
absence in living reptiles. It is not known whether the extremity of the
Pterodactyle's beak is a single bone, the intermaxillary bone, such as
forms the corresponding toothless part of the jaw in the South African
reptile Dicynodon, or whether it is made by the pair of bones called
premaxillaries which form the extremity of the jaw in most Dinosaurs.
Too much importance may perhaps be attached to such differences which
are partly hypothetical, because the extinct Ichthyosaurus, which has an
exceptionally long snout, has the two premaxillary bones elongated so as
to extend backward to the nostrils. A similar elongation of those bones
is seen in Porpoises, which also have a long snout; and the bones are
carried back from the front of the head to the nostrils, which are
sometimes known as blowholes. But the Porpoise has those premaxillary
bones not so much in advance of the bones which carry teeth named
maxillary, as placed in the interspace between them. The nostrils,
however, are not limited to the extremity of the head in all Dinosaurs.
If this region of the beak in Dimorphodon be compared with the
corresponding part of a Dinosaur from the Permian rocks, or Trias, the
relation of the nostril to the bones forming the beak may be better
understood.

  [Illustration: FIG. 78.  COMPARISON OF THE SKULL OF THE DINOSAUR
  ORNITHOSUCHUS WITH THE ORNITHOSAUR DIMORPHODON]

In the sandstone of Elgin, usually named Trias, a small Dinosaur is
found, which has been named Ornithosuchus, from the resemblance of its
head to that of a Bird. Seen from above, the head has a remarkable
resemblance to the condition in Rhamphorhynchus, in the sharp-pointed
beak and positions of the orbits and other openings. In side view the
orbits have the triangular form seen in Dimorphodon, and the preorbital
vacuities are large, as in that genus, while the lateral nostrils, which
are smaller, are further forward in the Dinosaur. The differences from
Dimorphodon are in the articulation for the jaw being carried a little
backward, instead of being vertical as in the Pterodactyle, and the bone
in front of the nose is smaller. Notwithstanding probable differences
in the palate, the approximation, which extends to the Crocodile-like
vacuity in the lower jaw, is such that by slight modification in the
skull the differences would be substantially obliterated by which the
skull of such an Ornithosaur is technically distinguished from such a
Dinosaur.

The back of the skull is clearly seen in the Whitby Pterodactyle, and
its structure is similar to the corresponding part of such Dinosaurs as
Anchisaurus or Atlantosaurus, without the resemblance quite amounting to
identity, but still far closer than is the resemblance between the same
region in the heads of Crocodiles, Lizards, Serpents, Chelonians. Few of
these fossil Dinosaur skulls are available for comparison, and those
differ among themselves. The coincidences rather suggest a close
collateral relation than prove the elaboration of one type from the
other. They may have had a common ancestor.

The Trias rocks near Stuttgart have yielded Dinosaurs as unlike
Pterodactyles as could be imagined, resembling heavily armoured
Crocodiles, in such types as the genus Belodon. Its jaws are compressed
from side to side, as in many Pterodactyles, and the nostrils are at
least as far backward as in Rhamphorhynchus. Belodon has preorbital
vacuities and postorbital vacuities, but the orbit of the eye is never
large, as in Pterodactyles. It might not be worth while dwelling on such
points in the skull if it were not that the pelvis in Belodon is a basin
formed by the blending of the expanded plates of the ischium and the
pubis, into a sheet of bone which more nearly resembles the same region
in Pterodactyles than does the ischio-pubic region in other Dinosaurian
animals like Cetiosaurus.

The backbone in a few Dinosaurs is suggestive of Pterodactyles. In such
genera as have been named Coelurus and Calamospondylus, in which the
skeleton is only partially known, the neck vertebræ become elongated, so
as to compare with the long-necked Pterodactyles. The cervical rib is
often very similar to that type, and blended with the vertebra, as in
Pterodactyles and Birds. The early dorsal vertebræ of Pterodactyles
might almost be mistaken for those of Dinosaurs. The tail vertebræ of a
Pterodactyle are usually longer than in long-tailed Dinosauria.

In the limbs and the bony girdles which support them there is more
resemblance between Pterodactyles and Dinosaurs than might have been
anticipated, considering their manifest differences in habit. Thus all
Dinosaurs have the hip bone named ilium prolonged in front of the
articulation for the femur as well as behind it, almost exactly as in
Pterodactyles and Birds (see p. 95). There is some difference in the
pubis and ischium which is more conspicuous in form than in direction of
the bones. There is a Pterodactyle imperfectly preserved, named
_Pterodactylus dubius_, in which the ischium is directed backward and
the pubis downward, and the bones unite below the acetabular cavity for
the head of the femur to work in, but do not appear to be otherwise
connected. In Rhamphorhynchus the connexion between these two thickened
bars is made by a thin plate of bone. In such a Dinosaur as the American
carnivorous Ceratosaurus the two bars of the pubis and ischium remain
separate and diverging, and there is no film of bone extending over the
interspace between them. The development of such a bony condition would
make a close approximation between the Ornithosaurian pelvis and that
of those Dinosaurs which closely resemble Pterodactyles in skull and
teeth.

  [Illustration: FIG. 79.  LEFT SIDE OF PELVIS
  A Pterodactyle is shown between a carnivorous Dinosaur above and a
  herbivorous Dinosaur below]

Another pelvic character of some interest is the blending of the pubis
and ischium of the right and left sides in the middle line of the body.
There are some genera of Dinosaurs like the English Aristosuchus from
the Weald, and the American genera Coelurus, Ceratosaurus, and others,
in which the pubic bones, instead of uniting at their extremities, are
pinched together from side to side, and unite down the lower part of
their length, terminating in an expanded end like a shoe, which is seen
to be a separate ossification, and probably formed by a pair of
ossifications joined in the median line. This small bone, which is below
the pubes, and in these animals becomes blended with them, we may regard
as a pair of prepubic bones like those of Pterodactyles and Crocodiles,
except that they have lost the stalk-like portions, which in those
animals are developed to compensate for the diminished length of the
pubic bones. The prepubic bones may also be developed in Iguanodon, in
which a pair of bones of similar form remains throughout life in advance
of the pubes, as in Pterodactyles. In those Dinosauria with the
Bird-like type of pelvis the pubic bone is exceptionally developed,
sending one process backward and another process forward, so that there
is a great gap between these diverging limbs to the bone. In the region
behind the sternum to which the ribs were attached, and in front of the
pelvis, is a pair of bones in Iguanodon shaped like the prepubic bones
of Dimorphodon. They have sometimes been interpreted as a hinder part of
the sternum, but may more probably be regarded as a pair of prepubic
bones articulating each with the anterior process of the pubis (see Fig.
80). The small bones found at the extremities of the pubes in such
carnivorous Dinosaurs as Aristosuchus are blended by bony union with the
pubes. The bones in Iguanodon are placed behind the sternal region
without any attachment for sternal ribs, and the expanded processes
converge forwards from the stalk and unite exactly like the prepubic
bones of Ornithosaurs. While this character, on the one hand, may link
Pterodactyles with the Dinosaurs, on the other hand it may be a link
between both those groups and the Crocodiles, in which the front pair of
bones of the pelvis has also appeared to be representative of the
prepubic bones of Flying Reptiles (see Fig. 32, p. 98).

  [Illustration: FIG. 80.  DIAGRAM OF THE PELVIS SEEN FROM BELOW IN AN
  ORNITHOSAUR AND A DINOSAUR]

The resemblances between Pterodactyles and Dinosaurs in the hind limb
are not of less interest, though it is rather in the older Pterodactyles
such as Dimorphodon, Pterodactylus, and Rhamphorhynchus that the
resemblance is closest with the slender carnivorous Dinosaurs. They
never have the head of the thigh bone, femur, separated from its shaft
by a constricted neck, as in the Pterodactyles from the Chalk. In many
ways the thigh bone of Dinosaurs tends towards being Avian; while that
of Pterodactyles inclines towards being Mammalian, but with a tendency
to be Bird-like in the older types, and to be Mammal-like in the most
recent representatives of the group in the Chalk.

The bones of the leg in Ornithosaurs, known as tibia and fibula, are
remarkable for the circumstance first that they resemble Birds in the
fibula being slender and only developed in its upper part towards the
femur, and secondly that in a genus like Dimorphodon this drum-stick
bone has the two upper bones of the ankle blended with the tibia, so as
to form a rounded pulley joint which is indistinguishable from that of a
Bird (see p. 102). There is a large number of Dinosaurs in which this
remarkable distinctive character of Birds is also found. Only, Dinosaurs
like Iguanodon, for instance, have the slender fibula as long as the
tibia, and contributing to unite with the separate ankle bones of the
similarly rounded pulley at the lower end. There are no Birds in which
the tarsal bones remain separated and distinct throughout life. But in
Pterodactylus from Solenhofen, as in a number of Dinosaurs, especially
the carnivorous genera, the bones of the tarsus remain distinct
throughout life, and never acquired such forms as would have enabled the
ankle bone, termed astragalus, to embrace the extremity of the tibia, as
it does in Iguanodon. Thus the resemblance of the Ornithosaur drum-stick
is almost as close to Dinosaurs as to Birds.

There is great similarity between Dinosaurs and Pterodactyles seen in
the region of the instep, known as the metatarsus. These bones are
usually four in number, parallel to each other, and similar in form.
They are commonly longer than in Dinosaurs; but among some of the
carnivorous Dinosaurs their length approximates to that seen in
Pterodactyles. In neither group are the bones blended together by bony
union, while they are always united in Birds, as in Oxen and similar
even-hoofed mammals. Dinosaurs agree with Pterodactyles in maintaining
the metatarsal bones separate, but they differ from them and agree with
Birds frequently, in having the number of metatarsal bones reduced to
three, as in Iguanodon, though Dinosaurs often have as many as five
digits developed.

The toe bones, the phalanges of these digits of the hind limb, are
usually longer in Pterodactyles than in Dinosaurs, but they resemble
carnivorous Dinosaurs in the forms of their sharp terminal bones for the
claws, which are similarly compressed from side to side.

So diverse are the functions of the fore limb in Dinosaurs and
Pterodactyles, and so remarkably does the length of the metacarpal
region of the back of the hand vary in the long-tailed and short-tailed
Ornithosaurs, that there is necessarily a less close correspondence in
that region of the skeleton between these two groups of animals; for the
Pterodactyle fore limb is modified in relation to a function which can
only be paralleled among Birds and Bats; and yet neither of those groups
of animals approximates closely in this region of the skeleton to the
Flying Reptile. Under all the modifications of structure which may be
attributed to differences of function, some resemblance to Dinosaurs may
be detected, which is best evident in the upper arm bone, humerus; is
slight in the fore-arm bones, ulna and radius; and becomes lost towards
the extremity of the limb.

If the tendency of the thigh bone to resemble a Mammalian type of femur
(p. 100) is a fundamental, deep-seated character of the skeleton, it
might be anticipated that a trace of Mammalian character would also be
found in the humerus. For what the character is worth, the head of the
humerus does show a closer approximation to a Monotreme Mammal than is
seen in Birds, and is to some extent paralleled in those South African
reptiles which approximate to Mammals most closely. Not the least
remarkable of the many astonishing resemblances of these light aerial
creatures to the more heavy bodied Dinosaurs is the circumstance that
the humerus in both groups makes a not dissimilar approach to that of
certain Mammals.

These illustrations may be accepted as demonstrating a relationship
between the Ornithosaurs and Dinosaurs now compared, which can only be
explained as results of influence of a common parentage upon the forms
of the bones. But more interesting than resemblances of that kind is the
similarity that may be traced in the way in which air is introduced into
cavities in the bones in both groups. In some of the imperfectly known
Dinosaurs, like Aristosuchus, Coelurus, and Thecospondylus, the bone
texture is as thin as in Pterodactyles, and the vertebræ are excavated
by pneumatic cavities, which are amazing in size when compared with the
corresponding structures in birds, for the vertebra is often hollowed
out so that nothing remains but a thin external film like paper for its
thickness. In the Dinosaurian genus Coelurus this condition is as well
marked in the tail and back as it is in the neck. The essential
difference from Birds appears to be that in the larger carnivorous
Dinosaurs the pneumatic condition of the bones is confined to the
vertebral column; while Birds and Pterodactyles have the pneumatic
condition more conspicuously developed in the limb bones. The pneumatic
skeleton, however, appears to be absent from the herbivorous types like
Iguanodon and all Dinosaurs which have the Bird-like form of pelvis, and
are most Bird-like in the forms of bones of the hind limb. It is
possible that some of the carnivorous Dinosaurs also possessed limb
bones with pneumatic cavities. Many of those bones are hollow with very
thin walls. If their cavities were connected with the lungs the foramina
are inconspicuous and unlike the immense holes seen in the sides of the
vertebræ.

According to the late Professor Marsh, the limbs of Coelurus and its
allies, which at present are imperfectly known, are in some cases
pneumatic. Therefore there is a closer fundamental resemblance between
some carnivorous Dinosaurs and Pterodactyles than might have been
anticipated. But the skull of Coelurus is unknown, and the fragments of
the skeleton hitherto published are insufficient to do more than show
that the two types were near in kindred, though distinct in habit. Each
has elaborated a skeleton which owes much to the common stock which
transmitted the vital organs, and the tendency of the bones to take
special forms; but which also owes more than can be accurately measured
to the action of muscles in shaping the bones and the influence of the
mechanical conditions of daily life upon the growth of the bones in both
of these orders of animals. Enough is known to prove that all Dinosaurs
cannot be regarded as Ornithosaurs which have not acquired the power of
flight; though the evidence would lead us to believe that the primitive
Ornithosaur was a four-footed animal, before the wing finger became
developed in the fore limb as a means of extending a patagial membrane,
like the membrane which in the hind limb of Dimorphodon has bent the
outermost digit of the foot upward and outward to support the
corresponding organ of flight extending down the hind legs.

It may thus be seen that the characters of Ornithosaurs which have
already been spoken of as Reptilian, as distinguished from the
resemblances to Birds, may now with more accuracy be regarded as
Dinosaurian. The Dinosaurs, like Pterodactyles, must be regarded as
intermediate in some respects between Reptiles and Birds. The
resemblances enumerated would alone constitute a partial transition from
the Reptile to the Bird, although no Dinosaurs have organs of flight;
many are heavily armoured with plates of bone, and few, if any,
approximate in the technical parts of the skeleton to the Bird class,
except in the hind limbs. Yet Dinosaurs have sometimes been regarded as
standing to Birds in the relation of ancestors, or as parallel to an
ancestral stock.

Before an attempt can be made to estimate the mutual relation of the
Flying Reptiles to Dinosaurs on the one hand, and to Birds on the other,
it may be well to remember that the resemblance of such a Dinosaur as
Iguanodon to a Bird in its pelvis and hind limb is not more remarkable
than that of Pterodactyles to Birds in the shoulder-girdle and bones of
the fore limb. The keeled sternum, the long, slender coracoid bones and
scapulæ, are absolutely Bird-like in most Ornithosaurs; and that region
of the skeleton only differs from Birds in the absence of a furculum
which represents the clavicles, and is commonly named the
"merry-thought." The elongated bones of the fore-arm and the hand,
terminating in three sharp claws, are characters in which the fossil
bird Archæopteryx resembles the Pterodactyle Rhamphorhynchus, a
resemblance which extends to a similar elongation of the tail. It is
remarkable that the resemblance should be so close, since Archæopteryx
affords the only bird's skeleton known to be contemporary which can be
compared with the Solenhofen Flying Reptiles. The resemblance may
possibly be closer than has been imagined. The back of the head of
Archæopteryx is imperfectly preserved in the region of the quadrate
bone, malar arch, and temporal vacuity. And till these are better known
it cannot be affirmed that the back of the head is more Reptilian in
Pterodactyles than in the oldest Birds. The side of the head in
Archæopteryx is distinguished by the nostril being far forward, the
vacuity in front of the orbit being as large as in the Pterodactyle
Scaphognathus from Solenhofen and other long-tailed Pterodactyles.

CHAPTER XVIII

HOW PTERODACTYLES MAY HAVE ORIGINATED

Ornithosauria have many characters inseparably blended together which
are otherwise distinctive of Reptiles, Birds, and Mammals, and
associated with peculiar structures which are absent from all other
animals. They are not quite alone in this incongruous combination of
different types of animals in the same skeleton. Dinosaurs, which were
contemporary with Ornithosaurs, approximate to them in blending
characters of Birds with the structure of a Reptile and something of a
Mammal in one animal. If an Ornithosaur is Reptilian in its backbone, in
the articular ends of each vertebra having the cup in front and ball
behind in the manner of Crocodiles, Serpents, and many Lizards, a
Dinosaur like Iguanodon, which had the reversed condition of ball in
front and cup behind in its early vertebræ, may be more Mammalian than
Avian in a corresponding resemblance of the bones to the neck in hoofed
Mammals. But while Pterodactyles are sometimes Mammalian in having the
head of the thigh bone moulded as in carnivorous Mammals and Man, the
corresponding bone in a Dinosaur is more like that of a Bird. And while
the Pterodactyle shoulder-girdle is often absolutely Bird-like, that
region in Dinosaurs can only be paralleled among Reptiles.

Such combinations of diverse characters are not limited to animals which
are extinct. There were not wanting scientific men who regarded the
Platypus of Australia, when first sent to Europe, as an ingenious
example of Eastern skill, in which an animal had been compounded
artificially by blending the beak of a Bird with the body of a Mammal.
Fuller knowledge of that remarkable animal has continuously intensified
wonder at its combination of Mammal, Bird, and Reptile in a single
animal. It has broken down the theoretical divisions between the higher
Vertebrata, demonstrating that a Mammal may lay eggs like a Reptile or
Bird, that the skull may include the reptilian characters of the malar
arch and pre-frontal and post-frontal bones, otherwise unknown in
Mammals and Birds. The groups of Mammals, Birds, and Reptiles now
surviving on the earth prove to be less sharply defined from each other
when the living and extinct types are considered together. But in
Pterodactyles, Mammal Bird and Reptile lose their identity, as three
colours would do when unequally mixed together.

This mingling of characteristics of different animals is not to be
attributed to interbreeding, but is the converse of the combination of
characters found in hybrid animals. It is no exaggeration to say that
there is a sense in which Mammal, Bird, Reptile, and the distinctive
structures of the Ornithosaur, have simultaneously developed from one
egg, in the body of one animal.

The differences between those vertebrate types of animals consist
chiefly in the way in which their organisation is modified, by one
strain of characters being eliminated so that another becomes
predominant, while a distinctive set of structures is elaborated in each
class of animals. The earlier geological history of the higher
Vertebrata is very imperfectly known, but the evidence tends to the
inference that the older representatives of the several classes
approximate to each other more closely than do their surviving
representatives, so that in still earlier ages of time the distinction
between them had not become recognisable. The relation of the great
groups of animals to each other, among Vertebrata, is essentially a
parallel relation, like the colours of the solar spectrum, or the
parallel digits of the hand. It was natural, when only the surviving
life on the earth was known, to imagine that animals were connected in a
continuous chain by successive descent, but Mammals have given no
evidence of approximation to Birds; and Birds discover no evidence that
their ancestors were Reptiles, in the sense in which that word is used
to define animals which now exist on the earth. When the variation which
animals attain in their maturity and exhibit in development from the egg
was first realised, it was imagined that Nature, by slow summing up and
accumulation of differences which were observed, would so modify one
animal type that it would pass into another. There is little evidence to
support belief that the changes between the types of life have been
wrought in that way. The history of fossil animals has not shown
transitions of this kind from the lower to higher Vertebrata, but only
intermediate, parallel groups of animals, analogous to those which
survive, and distinct from them in the same way as surviving groups are
distinct from each other. The circumstance that Mammals, Birds, and
Reptiles are all known low down in the Secondary epoch of geological
time, is favourable to the idea of their history being parallel rather
than successive. Such a conception is supported by the theory of
elimination of characters from groups of animals as the basis of their
differentiation. This loss appears always to be accompanied by a
corresponding gain of characters, which is more remarkable in the soft,
vital organs than in the skeleton. The gain in higher Vertebrates in the
bones is chiefly in the perfection of joints at their extremities; but
the gain in brain, lungs, heart, and other soft parts is an elaboration
of those structures and an increase in amount of tissue.

The resemblances of Ornithosaurs to Mammals are the least conspicuous of
their characters. Those seen in the upper arm bone and thigh bone are
manifestly not derived from Mammals. They cannot be explained as
adaptations of the bones to conditions of existence, because there is no
community of habit to be inferred between Pterodactyles and Mammals, in
which the bones are in any way comparable.

Other fossil animals show that a fundamentally Reptilian structure is
capable of developing in the Mammalian direction in the skull, backbone,
shoulder-girdle, hip-girdle, and limbs, so as to be uniformly Mammalian
in its tendencies. This is proved by tracing the North American Texas
fossils named Labyrinthodonts, through the South African Theriodonts,
towards the Monotremata and other Mammalia. Just as those animals have
obliterated all traces of the Bird from their skeletons, Birds have
obliterated the distinctive characters of Mammals. The Ornithosaur has
partially obliterated both. With a skull and backbone marked by typical
characters of the Reptile, it combines the shoulder-girdle and
hip-girdle of a Bird, with characters in the limbs which suggest both
those types in combination with Mammals.

The bones have been compared in the skeleton of each order of existing
Reptiles, and found to show side by side with their peculiar characters
not only resemblances to the other Reptilia, but an appreciable number
of Mammalian and Avian characters in their skeletons. The term
"crocodile," for example, indicates an animal in which the skeleton is
dominated by one set of peculiar characters. Crocodiles retain enough of
the characteristics of several other orders of reptiles to show that an
animal sprung from the old Crocodile stock might diverge widely from
existing Crocodiles by intensifying what might be termed its dormant
characters in the Crocodile skeleton. Comparing animals together bone by
bone it is possible to value the modifications of form which they put
on, and the resemblances between them, so as to separate the inherited
wealth of an animal's affinities with ancestors or collateral groups,
from the peculiar characters which have been acquired as an increase
based upon its typical bony possessions or osteological capital. There
is no part of the Pterodactyle skeleton which is more distinctly
modified than the head of the upper arm bone, which fits into the socket
between the coracoid bone and the shoulder-blade. The head of the
humerus, as the articular part is named, is somewhat crescent-shaped,
convex on its inner border, and a little concave on its outer border,
and therefore unlike the ball-shaped head of the upper arm bone in Man
and the higher Mammals. It is much more nearly paralleled in the little
group of Monotremata allied to the living Ornithorhynchus. In that sense
the head of the humerus in a Pterodactyle has some affinity with the
lowest Mammalia, which approach nearest to Reptiles. The character might
pass unregarded if it were not found in more striking development in
fossil Reptiles from Cape Colony, which from having teeth like Mammals
are named Theriodontia. In several of those South African reptiles the
upper arm bone approaches closer to the humerus in Ornithosaurs than to
Ornithorhynchus. Such coincidences of structure are sometimes dismissed
from consideration and placed beyond investigation by being termed
adaptive modifications; but there can be no hope of finding community of
habit between the burrowing Monotreme, the short-limbed Theriodont, and
the flying Pterodactyle which might have caused this articular part of
the upper arm bone to acquire a form so similar in animals constructed
so differently. If the resemblance in the humerus to Monotremes in this
respect is not to be attributed to burrowing, neither can the crescent
form of its upper articulation be attributed to flight; for in Birds the
head of the bone is compressed, but always convex, and Bats fly without
any approach to the Pterodactyle form in the head of the humerus. This
apparently trivial character may from such comparisons be inferred to be
something which the way of life of the animal does not sufficiently
account for. These deepest-seated parts of the limbs are slow to adapt
themselves to changing circumstances of existence, and retain their
characters with moderate variation of the bones in each of the orders
or classes of animals. It therefore is safer to regard Mammalian
characters, as well as the resemblances which Pterodactyles show to
other kinds of animals, as due to inheritance from a time when there was
a common stock from which none of these animals which have been
considered had been distinctly elaborated.

A few characters of Ornithosaurs are regarded as having been acquired,
because they are not found in any other animals, or have been developed
only in a portion of the group. The most obvious of these is the
elongated wing finger; but in some genera, like Dimorphodon, there is
also a less elongation of the fifth digit of the foot, and perhaps in
all genera there is a backward development of the first digit of the
hand, which is without a claw, and therefore unlike the clawed digit of
a Bat. An acquired character of another kind, which is limited to the
Cretaceous genera, is seen in the shoulder-blade being directed
transversely outward, so that its truncated end articulates by a true
joint with the early vertebræ of the back, and defended the cavity
inclosed by the ribs by a strong bony external arch. And finally, as the
animals later in time acquire short tails, and relatively longer limbs,
the bones of the back of the hand, termed metacarpals, acquire greater
and distinctive length, which is not seen in the long-tailed types like
Rhamphorhynchus.

These and such-like acquired characters distinguish the class of animals
from all groups with which it may be compared, and mark the possible
limits of variation of the skeleton within the boundary of the order.
But no further variation of these parts of the skeleton could make a
transition to another order of animals, or explain how the
Pterodactyles came into existence, because the characters which separate
orders and classes of animals from each other differ in kind from those
which separate smaller groups, named genera and species, of which the
order is made up. The accumulation of the characters of genera will not
sum up into the characters of an order or class.

In making the division of Vertebrate animals into classes the skeleton
is often almost ignored. Its value is entirely empirical and based upon
the observed association of the various forms of bones with the more
important characters of the brain and other vital organs. What is
understood as a Mammalian or Avian character in the skeleton is the form
of bone which is found in association with the soft vital organs which
constitute an animal a Mammal or a Bird.

The characters which theoretically define a Mammal appear to be the
enormous overgrowth of the cerebral hemispheres of the brain by which
the cerebrum comes into contact with the cerebellum, as among Birds.
This character distinguishes both groups of animals from all Reptiles,
recent and fossil. But in examining the mould of the interior of the
brain case it is rare to have the bones fitting so closely to the brain
as to prove that the lateral expansion below the cerebrum and cerebellum
is formed by the optic lobes of the brain. Otherwise the brain of a
Pterodactyle might be as like to the brain of Ornithorhynchus as it is
like that of a Bird (Fig. 19). But it is precisely in this condition of
arrangement of the parts of the brain that the specimens appear to be
most clear. The lateral mass of brain in specimens of Ornithosaurs from
the Lower Secondary rocks appears to be transversely divided into back
and front parts, which may be thought to correspond to the structures in
a Mammal brain named _corpora quadrigemina_, but to be placed as the
optic lobes are placed in Birds, and to have relatively greater
dimensions than in Mammals. No evidence has been observed of this
transverse division of the optic lobes of the brain in Pterodactyles
from the Chalk and Cretaceous rocks, and so far as the evidence goes
this part of the brain was shaped as in birds, but rather smaller.

The brain is the only soft organ in which a Mammalian character could be
evidenced. The uniformity in character of the brain throughout the group
in Mammals is remarkable, in reference to the circumstance that the
reproduction varies in type; the lowest, or Monotreme division, being
oviparous. If there is no necessary connexion between the Mammalian
brain and the prevalent condition under which the young are produced
alive, it may be affirmed also that there is no necessary connexion
between the form of the brain and the form of the bones, since the brain
cavity in Theriodont reptiles shows no resemblance to that of a Mammal,
while the bones are in so many respects only paralleled among
Monotremata and Mammalia. The variety of forms which the existing
Mammalian orders of animals assume, shows the astonishing range of
structure of the skeleton which may coexist with the Mammalian brain.
And therefore we are led to the conclusion that any other fundamental
modification of brain--such as distinguishes the class of Birds--might
also be associated with forms and structures of the skeleton which
would vary in similar ways. In other words, if for convenience we define
a Mammal by its form of brain, structure of the heart and lungs, and
provision for nutrition of the young, without regard to the covering of
the skin, which varies between the scales of a pangolin and the
practically naked skin of the whale--a bird might be also defined by its
peculiar conditions of brain and lungs, without reference to the
feathered condition of the skin, though the feathered condition extends
backward in time to the Upper Secondary rocks, as seen in the
Archæopteryx.

The Avian characters of Pterodactyles are the predominant parts of their
organisation, for the conditions of the brain and lungs shown by the
moulds of the brain case and the thin hollow bones with conspicuous
pneumatic foramina, give evidence of a community of vital structures
with Birds, which is supported by characters of the skeleton. If any
classificational value can be associated with the distribution of the
pneumatic foramina as tending to establish membership of the same class
for animals fashioned on the same plan of soft organs, the evidence is
not weakened when a community of structures is found to extend among the
bones to such distinctive parts of the skeleton as the sternum,
shoulder-girdle, bones of the fore-arm and fore-leg; for in all these
regions the Pterodactyle bones are practically indistinguishable from
those of Birds. This is the more remarkable because other parts of the
skeleton, such as the humerus and pelvis, show a partial resemblance to
Birds, while the parts which are least Avian, like the neck bones, have
no tendency to vary the number of the vertebræ, in the way which is
common among Birds, following more closely the formula of the seven
cervical vertebræ of Mammals.

It would therefore appear from the vital community of structures with
Birds, that Pterodactyles and Birds are two parallel groups, which may
be regarded as ancient divergent forks of the same branch of animal
life, which became distinguished from each other by acquiring the
different condition of the skin, and the structures which were developed
in consequence of the bony skeleton ministering to flight in different
ways; and with different habit of terrestrial progression, this extinct
group of animals acquired some modifications of the skeleton which Birds
have not shown. There is nothing to suggest that Pterodactyles are a
branch from Birds, but their relation to Birds is much closer, so far as
the skeleton goes, than is their relation with the flightless Dinosaurs,
with which Birds and Pterodactyles have many characters in common.

On the theory of elimination of character which I have used to account
for the disappearance of some Mammalian characters from the
Pterodactyle, that loss is seen chiefly in the removal of the parts
which have left a Reptilian articulation of the lower jaw with the
skull, and the articulation of the vertebræ throughout the vertebral
column by a modified cup-and-ball form of joint. The furculum of the
Bird is always absent from the Pterodactyle. No specimen has shown
recognisable clavicles or collar-bones. Judged by the standard of
existing life, Pterodactyles belong to the same group as Birds, on the
evidence of brain and lungs, but they belong to a different group on
account of the dissimilar modifications of the skeleton and apparent
absence of feathers from the skin.

The most impressive facts in the Pterodactyle skeleton, in view of these
affinities, are the structures which it has in common with Reptiles.
Some structures are fundamental, like the cup-and-ball articulation of
the vertebræ, which is never found in birds or mammals. Although not
quite identical with the condition in any Reptile, this structure is
approximately Lizard-like or Crocodile-like in the cup-and-ball
character. It shows that the deepest-seated part of the skeleton is
Reptile-like, though it may not be more Reptilian than is the vertebral
column of a Mammal, if comparison is made between Mammals and extinct
groups of animals known as Reptiles, such as Dinosaurs and Theriodontia.

The orders of animals which have been included under the name Reptilia
comprise such different structural conditions of the parts of the
skeleton which may be termed reptilian in Ornithosaurs, that there is
good reason for regarding the cup-and-ball articulation as quite a
distinctive Reptilian specialisation, in the same sense that the
saddle-shaped articulation between the bodies of adjacent vertebræ in a
bird is an Avian specialisation. From the theoretical point of view the
Ornithosaur acquired its Reptilian characters simultaneously with its
Avian and Mammalian characters.

There is nothing in the structure of the skeleton of the Dinosauria, to
which Ornithosaurs approximate in several parts of the body, which would
help to explain the cup-and-ball articulation of the backbone, if the
Flying Reptile were supposed to be an offshoot from the carnivorous
Dinosaurs.

The elimination of Reptile characters from so much of the skeleton, and
the substitution for them of the characters of Birds and Mammals, would
be of exceptional interest if there had been any ground for regarding
the flying animal as more nearly related to a Reptile than to a Bird.
But if the evidence from the form of the brain and nature of the
pneumatic organs seen in the limb bones accounts for the Avian features
of the skeleton, the Reptilian condition of the vertebral column helps
to show a capacity for variation, and that the fixity of type and
structure, which the skeleton of the modern Bird has attained, is not
necessarily limited to or associated with the vital organs of Birds.

The variation of the cup-and-ball articulation in the neck of a
Chelonian, which makes the third vertebra cupped behind, the fourth
bi-convex, the fifth cupped in front, and the sixth flattened behind,
shows that too much importance may be attached to the mode of union of
these bones in Serpents, Crocodiles, and those Lizards which have the
cup in front; for while in Lizards the anterior cup, oblique and
depressed, is found in most of its groups, the Geckos show no trace of
the cup-and-ball structure, and in that respect resemble the Hatteria of
New Zealand.

If, therefore, the cup-and-ball articulation of vertebræ in
Ornithosauria has any significance as a mark of affinity to Reptiles, it
could only be in approximation to those living Reptiles which possess
the same character, and would have it on the hypothesis that both have
preserved the structure by descent from an earlier type of animal. This
hypothesis is negatived by the fact that the cup-and-ball articulation
is unknown in the older fossil Reptiles.

Although the articulation for the lower jaw with the skull in
Ornithosaurs is only to be paralleled among Reptiles, the structure is
adapted to a brain case which is practically indistinguishable from that
of a Bird, except for the postorbital arch.

The hypothesis of descent, therefore, becomes impossible, in any
intelligible form, in explanation of distinctive character of the
skeleton. The hypothesis of elimination may also seem to be
insufficient, unless the potential capacity for new development be
recognised as concurrent, and as capable of modifying each region of the
skeleton, or hard parts of the animal, in the same way that the soft
organs may be modified. From which we infer that all structures, which
distinguish the several grades of organisation in modern
classifications, soft parts and hard parts alike, may come into
existence together, in so far as they are compatible with each other, in
any class or ordinal division of animals.

Although the young Mammal passes through a stage of growth in which the
brain may be said to be Reptilian, there is no good ground for inferring
that Mammal or Bird type of skeleton was developed later in time than
that of Reptiles. The various types of Fishes have the brains in general
so similar to those of Reptiles that it is more intelligible for all the
vertebrate forms of brain to have differentiated at the same time, under
the law of elimination of characters, than that there should be any
other bond of union between the classes of animals.

If we ask what started the Ornithosauria into existence, and created the
plan of construction of that animal type, I think science is justified
in boldly affirming that the initial cause can only be sought under the
development of patagial membranes, such as have been seen in various
animals ministering to flight. Such membranes, in an animal which was
potentially a Bird in its vital organs, have owed development to the
absence of quill feathers. Thus the wing membrane may be the cause for
the chief differences of the skeleton by which Ornithosaurs are
separated from Birds, for the stretch of wing in one case is made by the
skin attached to the bones, and in the other case by feathers on the
skin so attached as to necessitate that the wing bones have different
proportions from Ornithosaurs.

It is a well-known observation that each great epoch of geological time
has had its dominant forms of animal life, which, so far as the earth's
history is known now, came into existence, lived their time, and were
seen no more. In the same way the smaller groups of species and genera
included in an ordinal group of animals or class have abounded, giving a
tone to the life of each geological formation, until the vitality of the
animal is exhausted, and the species becomes extinct or ceases to
preponderate. This process is seen to be still modifying the life on the
earth, when some kinds of animals and plants are introduced to new
conditions. Plants appear to wage successful war more easily than
animals. The introduction of the Cactus in some parts of Cape Colony has
locally modified both the fauna and flora, just as the Anacharis
introduced into England spread from Cambridge over the whole country,
and became for many years the predominant form of plant life in the
streams. The Rabbit in Australia is a historic pest. Something similar
to this physical fertility and increase appears to take place under new
circumstances in certain organs within the bodies of animals, by the
development of structures previously unknown. A familiar example is seen
in the internal anatomy of the Trout introduced into New Zealand, where
the number of pyloric appendages about the stomach has become rapidly
augmented, while the size and the form of the animal have changed. The
rapidity with which some of these changes have been brought about would
appear to show that Nature is capable of transforming animals more
rapidly than might have been inferred from their uniform life under
ordinary circumstances. Growth of the vital organs in this way may
modify the distinctive form of any vital organ, brain or lungs, and thus
as a consequence of modification of the internal structures due to
changes of food and habit, bring a new group of animals into existence.
And just as the group of animals ceases to predominate after a time, so
there comes a limit to the continued internal development of vital
structures as their energy fails, for each organ behaves to some extent
like an independent organism.

Under such explanations of the mutual relations of the parts of animals,
and groups of animals, time ceases to be a factor of primary importance
in their construction or elaboration. The supposed necessity for
practically unlimited time to produce changes in the vital organs which
separate animals into great orders or classes is a nightmare, born of
hypothesis, and may be profitably dismissed. The geological evidence is
too imperfect for dogmatism on speculative questions; but the nature of
the affinities of Ornithosaurs to other animals has been established on
a basis of comparison which has no need of theory to justify the facts.
It is not improbable that the primary epoch of time, even as known at
present, may be sufficiently long to contain the parent races from which
Ornithosaurs and all their allies have arisen.

In thus stating the relation of Ornithosaurs to other animals the Flying
Reptile has been traced home to kindred, though not to its actual
parents or birthplace. There is no geological history of the rapid or
gradual development of the wing finger, and although the wing membrane
may be accepted as its cause of existence, the wing finger is powerfully
developed in the oldest known Pterodactyles as in their latest
representatives.

Pterodactyles show singularly little variation in structure in their
geological history. We chronicle the loss of the tail and loss of teeth.
There is also the loss of the outermost wing digit from the hind foot as
a supporter of the wing membrane. But the other variations are in the
length of the metacarpus, or of the neck, or head. One of the
fundamental laws of life necessitates that when an animal type ceases to
adapt its organisation and modify its structures to suit the altered
circumstances forced upon it by revolutions of the earth's surface its
life's history becomes broken. It must bend or break.

The final disappearance of these animals from the earth's history in the
Chalk may yet be modified by future discoveries, but the Flying Reptiles
have vanished, in the same way as so many other groups of animals which
were contemporary with them in the Secondary period of time. Such
extinctions have been attributed to catastrophes, like the submergence
of land, so that the habitations of animals became an area gradually
decreasing in size, which at last disappeared. It appears also to be a
law of life, illustrated by many extinct groups of animals, that they
endure for geological ages, and having fought their battle in life's
history, grow old and unable to continue the fight, and then disappear
from the earth, giving place to more vigorous types adapted to live
under new conditions.

The extinct Pterodactyles hold a relation to Birds in the scheme of life
not unlike that which Monotremata hold to other Mammals. Both are
remarkable for the variety of their affinities and resemblances to
Reptiles. The Ornithosauria have long passed away; the Monotremes are
nearing extinction. Both appear to be supplanted by parallel groups
which were their contemporaries. Birds now fill the earth in a way that
Flying Reptiles never surpassed; but their flight is made in a different
manner, and the wing is extended to support the animal in the air,
chiefly by appendages to the skin.

If these fossils have taught that Ornithosaurs have a community of soft
vital organs with Dinosaurs and Birds, they have also gone some way
towards proving that causes similar to those which determined the
structural peculiarities of their bony framework, originated the special
forms of respiratory organs and brain which lifted them out of
association with existing Reptiles.

These old flying animals sleep through geological ages, not without
honour, for the study of their story has illuminated the mode of origin
of animals which survive them, and in cleaving the rocks to display
their bones we have opened a new page of the book of life.

APPENDIX

The best public collections of Ornithosaurian remains in England are
in the British Museum (Natural History); Museum of Practical Geology,
Royal College of Surgeons; the University Museum, Oxford; Geological
Museum, Cambridge; and the Museum of the Philosophical Society at
York.

Detailed descriptions and original figures of the principal specimens
mentioned or referred to may be found in the following writings:--

  H. v. Meyer, _Reptilien aus dem Lithograph_. _Schiefer_. 1859. Folio.
  v. Quenstedt, _Pterodactylus suevicus_. 1855. 4to.
  Goldfuss, _Nova Acta Leopold_. XV.
  v. Munster, _Nova Acta Leopold_. XV.
  A. Wagner, _Abhandl. Bayerischen Akad._, vi., viii.
  Cuvier, _Annales du Museum_, xiii. 1809.
    "     _Ossemens fossiles_, v. 1824.
  Buckland, _Geol. Trans._, ser. 2, iii.
  R. Owen, _Palæontographical Society_. 1851, 1859, 1860, 1870, 1874.
  K. v. Zittel, _Palæontographica_, xxix. 1882.
  T. C. Winkler, _Mus. Teyler Archives_. 1874, 1883.
  Oscar Fraas, _Palæontographica_, xxv. 1878.
  Anton Fritsch, _Böhm. Gesell. Sitzber_. 1881.
  R. Lydekker, _Catalogue of Fossil Reptilia in British Museum_ I. 1888.
  O. C. Marsh, _Amer. Jour. Science_. 1882, 1884.
  S. W. Williston, _Kansas University Quarterly_. 1893, 1896.
  E. T. Newton, _Phil. Trans. Royal Soc._ 1888, 1894.
  H. G. Seeley, _Ornithosauria_. 8vo. 1870.
      "         _Annals and Mag. Natural Hist._ 1870, 1871, 1890, 1891.
      "         _Linn. Society_. 1874, 1875.
      "         _Geol. Mag._ 1881.
  Felix Pleininger, _Palæontographica_. 1894, 1901.

INDEX

A

  Abdominal ribs, 85, 154

  Accumulation of characters, 220

  Acetabulum, 95

  Acquired characters, 219

  Adjacent land, 136

  Air cells, 10, 48

  Albatross, 23, 36, 176

  Alligator, brain, 53;
    pelvis, 98

  American Greensand, 185

  -- ornithosaurs, 87, 126

  Amphibia, 4, 191

  Anabas, 17

  Anacharis, 227

  Anchisaurus, 199

  Angle of lower jaw, 75

  Ankle bones, 103, 195, 207

  Anomodonts, 192

  Ant-eater of Africa, 142;
    India, 40;
    South America, 40, 185

  Apteryx, lungs, 48;
    pelvis, 95

  Aquatic mammals, 141

  Aramis, scapular arch, 113

  Archæopteryx, 58, 76, 104, 130, 197, 211

  Aristosuchus, 129, 190, 205, 209

  Armadillo, 40, 141

  Articulation of the jaw, 12, 75

  Ashwell, 177

  Atlantosaurus, 202

  Atlas and axis, 80, 81

  Aves, 190

  Avian characters, 220, 222

B

  Backbone, 78, 84

  Banz, 148

  Barbastelle, 25

  Barrington, 177

  Barton, 177

  Bat, 38, 110, 197;
    sternum of, 107;
    metacarpus, 128

  Bavaria, 156, 185

  Beak, horny, 74, 178

  Bear, skull of, 12;
    femur, 100

  Bel and the Dragon, 15

  Belodon, 202

  Bird, 80, 110, 120

  -- resemblances, 63, 65, 71, 95, 102, 108, 113, 119, 120, 211

  Bird-reptile, 188

  Bird wing, 128, 130

  Birds in flight, 22;
    with teeth, 76

  Black-headed bunting, 47

  Blainville, D. de, 30, 193

  Blood, temperature of, 56

  Bohemia, 34

  Bonaparte, Prince Charles, 30

  Bones of birds, variation in, 41

  -- of reptiles, variation in, 42

  -- about the brain, 69

  -- in the back, 84

  Bone texture, 59, 209

  Bonn Museum, 32, 85, 156

  Brain and breathing organs, 55

  Brain cavity, in birds and reptiles, 52;
    in mammals, 221, 226;
    in Solenhofen pterodactyles, 54, 220

  Brazil, 34

  Breathing organs, 8

  Bridgewater Treatise, 143

  British Museum, 133, 183

  Brixton, Isle of Wight, 55, 174

  Buckland, Dean, 143, 148, 231

  Burrowing limb, 38

C

  Cactus, 227

  Calamospondylus, 203

  Cambridge Greensand, 33, 89, 176

  -- Museum, 177

  Camel, 83

  Campylognathus, 68, 71, 135;
    size of, 149

  Canary, 47

  Carnivorous dinosaurs, 129

  Carpus, 122

  Caudal fin, 91, 161

  -- vertebræ, 89, 92, 203

  Ceratodus, 4, 5, 9, 17

  Ceratosaurus, 203, 204

  Cervical rib, 81

  Cetacea, 40

  Cetiosaurus, 198, 203

  Chalinolobus, 25

  Chalk, pterodactyles in, 136;
    of Kansas, 103, 132

  Chameleon, 17, 51, 70;
    scapula, 112;
    sternum, 107

  Chameleonoidea, 191

  Cheek bones, 178

  Chelonia, 86, 112, 193

  Chesterton, 177

  Chlamydosaurus, 21

  _Chrysochloris capensis_, 121

  Classification, 192;
    on pelvis characters, 195;
    of dinosaurs, 198

  Clavicles, 111, 112

  Claw, 105, 116, 183, 208

  Coelurus, 203, 209

  Coldham Common, 177

  Collar bone, 111

  Collini, 27

  Comparison with dinosaurs, 198;
    of pelvis, 204, 206;
    of skulls, 192, 199, 201

  Cope, Professor, 31, 34

  Coracoid, 109, 112, 113

  Cordylomorpha, 191

  Cormorant, 70, 174;
    sternum, 108

  Corpora quadrigemina, 221

  Crisp, Dr., on pneumatic skeleton, 47

  Crocodile, characters of, 217;
    heart, 56;
    lung, 9;
    shoulder-girdle, 111;
    skull, 46;
    vertebræ, 79

  Crocodilia, 190

  Curlew, 68

  Cuvier, 1, 27, 28, 54, 76, 77, 130, 231

  Cycnorhamphus, 70, 94, 171, 173, 204

  _Cycnorhamphus Fraasii_, 80, 96, 169

  -- _suevicus_, 169, 170

  Cypselus, 42

D

  _Dacelo gigantea_, 63

  Darwin, 3

  Davy, Dr. John, 142

  Deuterosaurus, 97

  Dicynodon, 200

  _Dicynodon lacerticeps_, 71

  Digits, of ostrich, 23;
    of pterodactyle, 128

  Digits with claws, 130;
    foot bones in, 105

  Dimorphodon, 63, 64, 66, 67, 73, 74, 83, 90, 102, 113, 143, 192, 194,
          199, 201, 206

  Dinosauria, 6, 77, 84, 87, 95, 129, 144, 198, 209

  Dinosaurs from Lias, 135, 192;
    from Elgin, 201, 207;
    Stuttgart, 202;
    Trias dinosaurs, 199, 200

  Diopecephalus, 168

  Diving birds, 23, 83, 102

  Dolichosauria, 191

  Dolphin, 107

  Doratorhynchus, 173

  Dorygnathus, 74, 148

  Dragons, 3, 15, 17

  Drumstick bone, 103, 195

  Duck, 22, 83

E

  Echidna, 75, 76, 95, 100

  Edentata, 185

  Edentulous beak, 153

  Eichstädt, 32

  Elephant, head of, 46

  Enumeration of characters, 223, 225

  Ephesus, winged figure, 16

  Epiphysis to first phalange, 123

  Exocoetus, 18

  Extinctions, 129

  Eye hole, 144;
    sclerotic bones in, 65

F

  Farren, William, 34

  Femur, 100

  Fibula, 102, 183, 206

  Fifth outer digit, 132;
    in foot, 145

  Figure from temple at Ephesus, 16

  First phalange, 151

  Fish-eating crocodile, 137

  Flight, organs of, 17;
    in bats, 25

  Flying limb, 38

  Flying fishes, 18, 57;
    foxes, 26;
    frogs, 19, 197;
    gecko, 21, 24;
    lizards, 20;
    reptiles, 37, 46;
    squirrel, 24

  Foot, 104;
    digits in, 105, 146

  Fore leg, 102, 206

  -- limb, 38, 107, 116, 120

  Four claws, 147

  Fox, Rev. W., 55, 174

  Fraas, Professor Oscar, 172, 231

  Frigate bird, vertebræ of, 86, 174

  Frog, lungs of, 8

  Furculum, 114

G

  Gaudry, Professor A., 31

  Gavial, 136

  Gecko, 21, 23

  Genera, comparison of, 192

  Geological distribution, 186

  Gills, 4

  Giraffe, 38, 39

  Glossy starling, 47

  Golden eagle, 120

  -- mole, 121

  Goldfuss, 30, 231

  Granchester, 177

  Great ant-eater, 40, 185

  Guillemot, 102

  Gull, 22

H

  Haarlem, Teyler Museum at, 32

  Habits, probable, 134, 176, 198

  Hairless skins, 141

  Hand in mammals, 38

  Harston, 177

  Haslingfield, 177

  Hastings, 174

  Hatteria lung, 9, 27;
    brain, 53;
    skull, 70, 77;
    ribs, 86;
    a reptile type, 13

  Head, characters of, 76

  Heidelberg Museum, 32, 54, 159

  Herpetomorpha, 191

  Heron, 65, 174

  Hesperornis, 76

  Hind foot, 104, 135

  -- limb, 93, 99, 159, 206

  Hip-girdle in whale tribe, 39, 159

  Homoeosauria, 191

  Horningsea, 177

  Horse, metacarpus of, 127;
    vertebræ of, 79

  Humerus, 46, 117, 217

  Huxley, Professor, 31, 89, 154, 188

  Hyo-mandibular arch, 13

  Hypothesis of descent, 226

  Hyrax, 101

  Ichthyornis, 76

  Ichthyosaurus, 6, 191

  Iguanodon, 209;
    pelvis, 206

  Ilium, 93, 95, 96, 98, 204

  Instep, 105, 207

  Inherited characters, 217

  Interclavicle, 111

  Ischium, 93, 96, 203, 204

  Isle of Wight, 174

J

  Jaw, in birds, 12;
    in fishes, 13;
    in mammals, 12;
    in reptiles, 13;
    in pterodactyles, 63;
    suspension of, 11, 74, 76

  -- lower, 75

K

  Kansas, Chalk of, 72, 103, 115;
    University Museum of, 181

  Kelheim, 32

  Keuper, 33

  Kimeridge Clay, 132

  Kingfisher, 63

  Kiwi, 23

L

  Labyrinthodontia, 191

  Lachrymal bones, 67

  Laramie rocks, 34

  Largest ornithosaur, 133

  Lateral vacuities in skull, 147

  Lawrence in Kansas, 181

  Lengths of bones, 146

  Lepidosiren, 17

  Lias, 33

  Lithographic Slate, 35, 156

  Lizards, 20, 21, 27, 123

  Llama, neck of, 79, 83

  Loach, swim bladder of, 52

  Lower jaw, 12, 74, 76, 149

  Lumbar vertebræ, 89

  Lungs, 47;
    in apteryx, 48;
    in chameleon, 51;
    in ostrich, 49;
    in reptiles, 8, 9, 51

  Lydekker, R., 160, 169, 231

  Lyme Regis, 33

M

  Macrocercus, palate of, 71

  Malar bone, 67

  Mallard, 22

  Mammal, 8, 12, 24, 79, 53, 95

  Mammalia, 38, 141

  Mammalian characters, 12, 220

  Mammoth, 141

  Manis, 40, 57, 142

  Manubrium of sternum, 108, 109, 183

  Marrow bones in a bird, 134

  Marsh, Professor O. C., 31, 72, 90, 115, 121, 131, 140, 160, 165,
          180, 181, 210, 231

  Marsupial, 70, 94, 99

  Megalosaurus, 129, 198

  Merganser, 108

  Merry-thought, 114

  Metacarpus, 116, 124, 126, 128, 130

  Metatarsal bones, 104, 207, 208

  Meyer, Hermann von, 31, 45, 46, 85, 105, 108, 121, 160, 192, 231

  Moa of New Zealand, 35

  Mole, humerus, 38;
    sternum, 107

  Monotremes, 70, 94, 111, 121, 185, 218

  Mososaurus, 77

  Movement of the leg, 101

  Mugger, 137

  Munich Museum, 32, 159

  Munster, von, 231

  Muschelkalk, 184

  Museum, 32, 156, 231, 159;
    Natural History, 133, 231

  Myrmecophaga, 185

N

  Names of genera, 183

  Natural History Museum, 38, 231

  Neck, 79;
    in Dimorphodon, 145;
    in Giraffe, 39;
    in Llama, 79;
    in Pterodactyles, 80;
    in Whales, 39

  Newton, E. T., 55, 70, 158, 160, 201, 232

  New Zealand Bat, 25

  -- -- Hatteria, 68

  Niobrara rock, 183

  Nostril, bones round the, 62;
    small, 147

  Notarium, 87, 115

  Nothosauria, 192

  Nusplingen, 32

  Nyctodactylus, 115, 180

O

  Obliteration of characters, 216

  Opercular bones, 13

  Ophidia, 52, 191

  Optic lobes, 53, 221

  Organs of flight, 17

  Ornithischia, 190, 198

  Ornithocephalus, 166

  Ornithocheirus, atlas and axis, 81;
    brain, 55, 69;
    carpus, 124;
    cervical vertebra, 83, 179;
    claw phalange, 129;
    coracoid, 109;
    femur, 100;
    pelvis, 98;
    pubic bones, 194;
    sternum, 109;
    shoulder-girdle, 115;
    remains, 176;
    teeth, 74, 76;
    absence of teeth, 138

  _Ornithocheirus machærorhynchus_, 139;
    _microdon_, 139

  Ornithocheiroidea, 193

  Ornithodesmus, neck bones, 173, 175;
    coracoid, 109, 116;
    dorsal vertebræ, 86;
    remains of _O. latidens_, 173;
    _O. sagittirostris_, 175

  Ornithomorpha, 189

  Ornithorhynchus, 40, 53, 95, 117

  Ornithosauria, 30, 31, 50, 52, 58, 72, 89, 95, 104, 108, 125, 132,
          133, 143, 187, 190, 192, 216

  Ornithostoma, 66, 69, 72, 180;
    lower jaw, 75, 76;
    pelvis, 98;
    sternum, 110;
    phalange, 122;
    size, 133;
    skull, 181, 182

  Ornithosuchus, 201

  Orycteropus, 96

  _Ossa innominata_, 93

  Ossified ligaments, 150

  Ostrich, 23, 45, 49, 113, 129

  Owen, Sir R., 31, 36, 46, 48, 110, 117, 143, 172, 176, 180, 231

  Owl, 46, 53

  Oxford Clay, 33, 156

  -- University Museum, 154

  Ox, vertebra of, 79;
    metacarpus, 127

P

  Palate, bones of, 71

  Pangolin, 142

  Pappenheim, 32

  Parallel groups, 215

  Parrot, 71

  Patagial membranes, 227

  Pelican, 174

  Pelvis, 88, 94-98, 151, 195, 202, 204, 206

  Penguin, 41, 42, 104, 176

  Periophthalmus, 17

  Peterborough, bones from, 113, 156

  Phalanges, 129, 132;
    wing finger, 155

  Phillips, Professor John, 155

  Pigeon, 119

  Platydactylus, 21

  Platypus, 214

  Plesiosaurus, 6, 73, 75, 93, 189

  Pleininger, 149, 232

  Pneumatic foramina, 45, 83, 88, 132, 209

  Pond, Mr., 34

  Porcupine, 40

  Porpoise, 38, 73, 141, 200

  Premaxillary bones, 77, 200, 205

  Prepubic bones, 94, 96-98, 194, 204, 205

  Protorosauria, 192

  _Ptenodracon brevirostris_, 64, 99, 167, 169, 192

  Pterodactyle aspects, 35;
    avian characters, 222;
    beak, 200;
    brain, 53;
    coracoid, 113;
    discovery, 27, 33;
    foot, 104;
    fore limb, 117;
    history in Germany, 31, 148;
    hand, 130;
    hind limb, 100;
    long tails, 156;
    palate, 71;
    sacrum, 89;
    short tails, 165;
    size, 35, 133;
    sacrum, 89;
    skull, 192;
    teeth, 73;
    vertebræ, 80

  Pterodactyles from Kansas Chalk, 177, 181

  -- from Lias Clay, 135, 147, 152

  -- from Neocomian Sand, 176

  -- from Oxford Clay, 155

  -- from Purbeck beds, 173

  -- from Solenhofen Slate, 156, 158

  -- from Stonesfield Slate, 153, 158

  Pterodactylia, 30, 165, 193, 199

  _Pterodactylus antiquus_, 167;
    _brevirostris_, 99, 167, 169;
    _crassirostris_, 156;
    _dubius_, 87, 96, 97, 203;
    _elegans_, 169;
    _Fraasii_, 169;
    _grandipelvis_, 87, 90;
    _grandis_, 102, 167, 169;
    _Kochi_, 12, 61, 87, 90, 168, 169;
    _longirostris_, 28, 90, 96, 101, 103, 105, 167, 169;
    _micronyx_, 105, 169;
    _rhamphastinus_, 183;
    _scolopaciceps_, 105, 166;
    _spectabilis_, 83;
    _suevicus_, 169

  Pterodermata, 194, 199

  Pteroid bone of first digit, 121

  Pteromys, 24

  Pterosauria, 187, 193

  Pterygoid bones, 72, 147

  Pythonomorpha, 191

Q

  Quadrate bone, 12, 68, 77

  Quenstedt, 231

R

  Rabbit, 227

  Radius, 119, 120

  Redshanks, 22

  Relation between head and tail, 157, 193

  Reptile, 6, 79, 80

  Resin, 136

  Restorations--
    Campylognathus, palate of, 71
    Dimorphodon, 143, 147, 164
    Ornithocheirus, 164
    Ornithostoma, 164, 183
    Ptenodracon, 167
    Pterodactylus, 29, 30
    Rhamphocephalus, 164
    Rhamphorhynchus, 161, 164
    Scaphognathus, 163

  Rhacophorus, 19

  Rhætic beds, 184

  Rhamphocephalus, 113, 136, 153

  Rhamphorhynchus, 118, 192;
    foot, 104;
    hind limb, 99;
    pelvis, 95;
    sacrum, 88;
    skull, 54, 63-6, 69;
    sternum, 108;
    tail, 91;
    teeth, 73;
    tibia and fibula, 103;
    web-footed, 105

  _Rhamphorhynchus curtimanus_, 163;
    _hirundinaceus_, 163;
    _longimanus_, 164;
    _phyllurus_, 91, 165

  Rhinoceros, 40, 141

  Rhopoladon, 97

  Rhynchocephala, 192

  Roc, 36

  Rochester, 136

  Running limb, 38

  Ryle, Bishop, 17

S

  Sacrum, 87, 88

  St. George, 15

  St. Ives, 156

  Sarcorhamphus, 102

  Saurians, 27

  Saurischia, 190, 195, 198, 199

  Sauromorpha, 191, 192

  Sauropsida, 188

  Sauropterygia, 192

  Scaphognathus, 64, 85, 140, 152, 192, 212

  _Scaphognathus crassirostris_, 73-5, 83

  Scapular arch, 111, 113

  Scelidosaurus, 135

  Sclerotic circle, 65

  Seals, 41

  Sedgwick, Professor Adam, v, 46

  Shillington, 77

  Shoebill, 67

  Shoe-shaped prepubic bones, 204, 205

  Short-tailed pterodactyles, 165, 193

  Shoulder-girdle, 107, 111, 114, 115, 183

  Siberia, 141

  Simultaneous origin of characters, 214, 224

  Skin covering, 40, 41, 58, 139, 140

  Skulls, 68

  Sloth, 112

  Snipe, 47, 68

  Solenhofen Slate, 28, 32, 88, 153, 156

  Sömmerring, 29

  South African reptiles, 188, 208, 216

  Spotted fly-catcher, 47

  Squamosal bone, 12, 13

  Sternal ribs, 110

  Sternum, 107, 158

  Stonesfield Slate, 33, 88, 153

  Structures common to reptiles, 224

  Stuttgart Museum, 32, 172, 203

  Swanage, 172

  Swan, neck of, 80, 113

  Swift, 50

  Swimming limb, 38

  Synotus, 25

  Syrinx, 48

T

  Tail, description of, 90;
    in Cretaceous Pterodactyles, 193
    -- long, 156;
    short, 166;
    in Dimorphodon, 145;
    in Ornithocheirus, 179

  Tanystrophoeus, long vertebræ in, 79

  Tarsal bones, 102, 207

  Tarso-metatarsus, 128

  Teeth, 73, 137, 138;
    in porpoise, 40

  Temperature of blood, 56

  Temporal arches, 68

  -- bone, 12

  -- fossa, 67

  Teredo, 137

  Texas fossils, 216

  Thecospondylus, 209

  Theriodont pelvis, 97

  -- reptiles, 75;
    of Russia, 96, 97;
    of South Africa, 96, 117

  Theropsida, 188

  Thigh bone, 100, 206, 211

  Three claws, 146, 197

  Tibia, 102, 195;
    in Iguanodon, 207

  Toothless mammals, 40

  -- pterodactyles, 138, 181;
    beak of pterodactyles, 150

  Transition from reptiles to birds, 211

  Tree frogs, 21

  Trias dinosaurs, 199

  Triceratops, pelvis of, 204

  Trout, 139;
    of New Zealand, 228

  Tuatera, 13

  Tübingen Museum, 32

  Tundras, 141

  Tunny, 57

  Turtles, neck bones, 79

U

  Ulna, description of, 119

  Uncinate process of ribs, 85

  Unlimited time, 228

  Upper arm bone, 117

  -- Greensand, remains in, 136

  -- Lias of Whitby, 147

  -- Oolites, 185, 195

V

  Variation of bones in mammals, 38

  -- in Pterodactyles, 229

  Variation of bones in vertebræ, 225

  Vertebræ, caudal, 89, 92, 203

  -- cervical, 173, 179, 203

  -- dorsal, 86

  Vertebral articulation, 82, 224

  -- column, 78

  Vulture, neck vertebræ of, 80;
    tibia and fibula of, 102

  Vomer, 147

  Vomerine bones, 72

W

  Wagler, 29

  Wagner, Andreas, 30, 148, 231

  Walker, J. F., 54

  Wealden beds, Pterodactyles in, 55, 84;
    bones in, 135, 136, 173

  Weight of Pterodactyle, 106

  Whinchat, 47

  Whitby, 33, 135

  Williston, Professor W. S., 75, 82, 92, 98, 105, 110

  Willow-wren, 47

  Wing finger, 116, 130, 133, 151, 178, 197

  -- membrane, 32, 121, 140, and frontispiece

  -- metacarpal, 123;
    in Dimorphodon, 151;
    in Ornithostoma, 184;
    in bats, 131

  Wings of Dragons, 16

  Winkler, T. C., 231

  Woodwardian Museum, 34

  Wood-wren, 47

  Wrist bones, 122

  Würtemberg, 33

Y

  Yale College Museum, 32

  York Museum, 34, 176

Z

  Zittel, Karl von, 31, 157, 165, 231

  Zygomatic arch, 67

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  WILLIAM BRENDON AND SON
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