converging towards the crown, which however presents a broken and
worn surface. From side to side the squamosal and parietal bones are
concave, owing to the extended occipital crest behind, and the rapid
widening of the skull in front caused by the large size of the brain.
In _front_ is seen a section of the brain-cavity. It is very like in
form to the two halves of a pear put together side by side with the
stalk downward. I have removed some of the phosphate of lime from the
brain-cavity, and although it has not been excavated to the cerebellum,
the great depth of the brain is well seen, and the convex character of
the cerebral lobes, between which a crest of bone descends mesially as
in the ethmo-sphenoid mass next described. At each of the lower outer
angles of the brain, extending into the cancellous brain-walls to the
outermost film, is an ovoid convexity, covered with a thin film of
bone. They entirely correspond with the optic lobes, being in exactly
the same position as in birds, only relatively rather small. Underneath
the optic lobe on the outside is a small concavity, apparently the
articulation for the quadrate bone. The basi-sphenoid mass below the
brain is of considerable height, the upper half flat and smooth, the
lower half fractured and cancellous.
In the main this skull is like the other one, differing chiefly in the
depth of the sphenoid, in the mesial ridge between the cerebral lobes,
in showing the optic lobes, and in having anchylosed basi-temporal
bones. There would hence appear to have been considerable variations in
the skulls of Pterodactyles even in the Cambridge Greensand.
Orbito-ethmo-sphenoid bone.
Pl. 11.
Case. Comp. Tablet.
=J= _c_ 9
The symmetrical bone which I have so named is a wedge-like mass
tapering in front, keeled above; flattened below, and cupped behind
on each side. It belonged to a very much larger animal than the last
fossil, and probably to a very different genus.
The _inferior surface_ is triangular, an inch and an eighth wide
behind, at the base, and an inch and a quarter long; but it is broken
at both ends. In its longitudinal median line is a strong keel stopping
short in front, dying away behind, and forming with the compressed
margins a considerable hollow on each side, at the back part of which
is a large oval foramen. This surface, though five times the size,
corresponds in form, ridges, and foramina with the anterior part of the
sphenoid described in the article on the back of the cranium.
The _posterior surface_ is at right angles to the inferior one, but its
lower third shows only fractured phosphate of lime filling perhaps the
anterior part of the pituitary fossa. Its upper part also is broken.
But on each side is a large concavity measuring in the fractured fossil
an inch and a quarter high, three quarters of an inch wide, and half
an inch deep from the unbroken median ridge where the cups become
confluent at their base. The whole specimen is two and a quarter inches
high. From the determination of the under side it follows that these
smooth hollows, over each of which an impressed mesial line descends
obliquely outward, are a part of the anterior boundary of the brain.
From the middle of the outer convex border of the oval remains of
these cups for the cerebral hemispheres, a strong blunt ridge descends
obliquely down the sides of the bone to terminate the compressed
anterior end of the bone just in front of the hypapophysial ridge of
the sphenoid. Above this ridge the bone is much compressed anteriorly,
forming a strong straight mesial keel above, which rapidly approximates
to the base; the height of the bone in front being one inch and a half,
which is also its extreme length.
The region below the oblique ridge is a concavity, but it is a little
compressed from side to side behind, and has the same anterior
compression, so that the elongated oval of the fracture at the anterior
end of the bone is only three-eighths of an inch wide.
The superior ridge will probably have supported the frontals, and the
anterior end would terminate in the orbito-sphenoid.
The lateral ridges appear to correspond with what Prof. Huxley has
described in the Ostrich as the ridge indicative of a supra-presphenoid
ossification pointed out by Kölliker. The groove which is here noticed
on the cerebral surface may indicate the same division. If so, the
upper and anterior part of the mass would be the ethmoid.
This mass offers a considerable resemblance to the frontal portion
of the skull of a dolphin (_e. g._ Delphinus delphis) from which the
maxillary, premaxillary, palatine and nasal bones have been removed.
But in the Porpoise the mesial ridge dividing the cerebral hemispheres
is not prolonged so far forward as in the Pterodactyle; the cranial
bones are often as smooth on the inside. Notwithstanding Wagner's
assurance that the Pterodactyle skull is very like a Monitor's, he
would have looked in vain for an ossification in Monitor, Iguana, or
other Lizards, comparable with this mass. And although the brain is
closed in front by bones in Serpents, it is by the frontal bones,
which form a covering for nearly the whole of the conical cerebrum.
Nor in the Crocodile is there any ossified mass in front of the brain,
although the brain approximates nearer to Birds than is the case with
other living Reptiles. Among Birds such a structure as that of the
Pterodactyle is characteristic, but no bird has it so massive and
mammal-like, though an approximation is made in some thick-skulled
birds like _Ciconia marabou_. And in birds it usually is prolonged much
further forward than appears to have been the case with Pterodactyle,
where from the rapid tapering of the mass in front it appears to have
ended in a vertical ridge like that in Parrots and Birds with a
moveable beak. In Birds there is usually a median ridge dividing the
cerebral hemispheres, but there is also often a small olfactory lobe
prolonged in front of the cerebrum, to which nothing analogous is
indicated in these fossils.
NATURAL MOULD OF THE BRAIN CAVITY OF A CAMBRIDGE ORNITHOSAURIAN[U].
(Cast.)
Pl. 11.
[Footnote U: For the opportunity of making this description, I am
indebted to the kindness of John Francis Walker, Esq., M.A., F.G.S.,
F.C.S., &c., who some time since forwarded to me the whole of his rarer
Ornithosaurian remains for description in the Geological Magazine,]
The original specimen is in the collection of J. F. Walker, Esq., of
Sidney Sussex College. When found it only displayed the front of the
cerebral hemispheres, and Mr. Walker generously gave me permission to
remove the investing cancellous bone and phosphate of lime, and thus
exhibit the form of the cerebrum and its relations to the cerebellum.
The lower part of the brain is not preserved. But adherent to the sides
of the fossil are still left parts of the temporal bones, and part of
the bone at the back of the orbit which closes in the brain. The form
of the cerebellum is not quite perfect behind, but it must have been
unusually small.
The cerebral lobes taken together are much wider from side to side than
from back to front, and have a transverse elliptical outline, except
for the mesial notch behind for the cerebellum. The lobes are a little
flattened above, and divided from each other by a deep mesial groove,
which makes each lobe convex from side to side. They are well rounded
at the front and at the sides, and are a little compressed towards each
other below in the region of the orbits. Behind they become covered
superiorly as in birds with a greatly thickened part of the squamosal
and parietal bones. The surface of the cerebrum is smooth. There is
no indication of a pineal gland. The cerebellum is small, like a pea
between two filberts. It is sub-hemisphercal, is placed close against
the cerebrum, and appears to give off narrow lateral parts, like
those seen in many birds, only that they abut against the back of the
cerebral lobes as in the Hare and some Mammals. In no reptile is there
a brain in which the cerebrum embraces the front of the cerebellum,
or in which it attains to such an enormous size. Fœtal Mammals (_e.
g._ the horse and the sheep), even when they have attained to a
considerable bulk, and many adult mammals, still have the optic lobes
dividing the cerebrum from the cerebellum as in Reptiles.
The only Mammal which shows any near approximation to this brain is
the _Ornithorhynchus_, in which the cerebellum is very small, but the
cerebrum is not so well rounded in front. The form approximates to
the brain in Man. But with Birds the resemblance is so close--with
the owl and the goose--that there is no character to distinguish the
brain of the fossil animal from those of the recent ones. A section of
the cerebrum in this specimen entirely corresponds with a section of
the brain-cavity in the second skull described, as does the backward
extension of the cerebrum with the extent of the cerebral cavity, and
the narrow cerebellum with the narrow channel parallel to the walls
of the foramen magnum, as in _Gallus domesticus_ and Birds. The front
of the brain corresponds with the cast of the front of the cerebral
lobes taken from the Ethmo-sphenoid mass. Thus the specimens agree
among themselves, and prove the Pterodactyle to have had a brain
indistinguishable from that of a Bird. And when it is remembered how
distinctive this kind of brain is, and that it approximates rather
towards the higher Mammals than towards Reptiles, the fact attains
unusual importance in determining the Pterodactyle's place in nature.
?NEURAL ARCH OF SACRAL VERTEBRA, ?VOMER.
Pl. 12.
Frontal(?) Owen. _Palæontographical_, 1859
Pl. 4, fig. 6, 7, 8.
Case. Comp. Tablet. Specimen.
=J= _c_ 10 1-3
In 1859 Prof. Owen described with doubt as the Frontal
of Pterodactyle, a symmetrical bone. A smaller but more perfect
specimen has since been obtained for the Woodwardian
Museum; and a fragment of intermediate size is in the rich
collection of the Rev. T. G. Bonney. From the descriptions
already given it is impossible for it to be the frontal. There
is no proof that it is a skull bone. If of Pterodactyle the
compressed lateral spaces could only be part of the nasal passages,
or the impressions of a palatine or pterygoid articulation.
And as the external surface of every specimen is keeled, and
as the palatal surface of the upper jaw of every known Greensand
Pterodactyle is keeled, and as the concavities slightly converge
to the keel, it might be a bone from the under side of the
head,--the vomer.
The smallest specimen is a compressed sub-semicircular bone
1-1/4 inch long, 9/16 inch high, and a 1/4 inch thick. The under surfaces
converge to form a strong keel, which is flattened off behind.
Above this, the posterior third of the bone is compressed
obliquely to half the thickness, as though a bone had over-lapped
this area on each side. If the oval spaces are nares, that
bone might have been the pterygoid or palatine. Three-fifths
of the remainder of the bone are taken up by the smooth oval
depressions, which might be the inner walls of the nares; and above
this is a margin of bone widening into the triangular compressed
part in front, which, if the fossil is rightly determined, must have
fitted into the posterior end of the maxillary or anterior end of
the palatine bones.
A specimen collected by the Rev. T. G. Bonney is preserved on
the sacral side of a left _os innominatum_ with the keel downward.
It appears to show a sutural surface from which an anterior part
has come away. And if this specimen is compared with the
neural arch of the sacral vertebra =J=._c_.4.1, it will be found to
correspond entirely. It is not impossible that _c_.10.1, 2 may be
vomerine, and _c_.10.3 sacral, but there are no distinctive characters
between the specimens to warrant such a determination.
QUADRATUM.
Pl. II.
and Quadrato-Jugal.
Case. Comp. Tablet. Specimen.
=J= _c_ 11 1-4
In the Woodwardian Museum are two distal ends of the quadrate bone and
two other fragments showing the quadrato-jugal with it.
_Quadrate._ The smallest specimen is 1/2 an inch over the articular
surface for the lower jaw and a quarter of an inch thick. It is concave
from side to side in front where it shows a large pneumatic foramen
near the basal end; it is bent from the articulation a little backward.
It is convex behind; and between the foramen and the articulation sends
inward and forward a great wing like that of the quadratum in birds.
The specimens are broken short off and do not show any articulation
above, where the bone contracts.
The distal articulation is double, like two long cones placed together;
that in front having the base outward, while the hinder one has the
base on the inner side. The largest specimen, which is much broken,
shows the articulation half an inch thick.
_Quadrato-jugal._ This is a thin flat squamous bone, apparently of a
transverse diamond shape, which is anchylosed to the anterior lateral
margin of the quadrate, at right angles to the articulation. The lower
margin is straight, as is the upper anterior margin, which appears to
have received the malar bone above.
The upper posterior side is broken, but shows a large foramen near
to the side of the quadrate. The base of the diamond is at the
articulation, and at its apex is a small fragment of smooth surface,
either part of a foramen, or the orbit of the eye.
In this specimen the articulation, which is broken, is about 3/4 of an
inch wide, 3/8 of an inch thick. The remaining piece of the quadrate is
an inch long. The quadrato-jugal is an inch and 3/16 high, and between
its broken ends 1-3/4 inch long. It is thick and strong where joining
the quadrate, but the rest of the bone is about an 1/8th of an inch
thick.
The quadrate bone is Avian in possessing a pneumatic foramen, and Avian
in the form of so much of the distal end as is preserved, and in the
articulation for the lower jaw. The process which it sends inward on
the inside is probably for the pterygoid bone, after the manner of
Birds. Before anchylosis with the quadrato-jugal bone set in, as may
be seen in =J=._c_.11.4, the union was made by a hemispherical knob on
the outside of the quadrate, as in _Gallus domesticus_. The squamose
quadrato-jugal is a distinctive character.
?PTERYGOID END OF PALATINE BONE.
Pl. 12.
Case. Comp. Tablet. Specimen.
=J= _c_ 14 1-2
This determination is conjectural. Its form is such as would make it
probable that it is part of the head. A more perfect specimen is seen
in =J=._c_.1.2.7.
The best specimen is a compressed sub-quadrate fragment of bone
terminating at one end in a long reniform articular surface, and at
the other end in a fracture where the bone is rapidly thickening. A
side, regarded as the outer one, is flattened, being slightly concave
in length, and slightly convex from side to side. The form of the
inner side of the bone is determined by the inward curve of the thick
part of the articular surface, which sends a rounded ridge obliquely
on to the side, so that while it is concave from side to side at the
articulation, at the fracture it is convex from side to side. All the
specimens are large, the articulation being not less than an inch long.
PREMAXILLARY BONES
Pl. 12.
appear to be developed as in birds. An account of their structure will
be found in the notes on the species, page 112.
------------
OS ARTICULARE AND PROXIMAL END OF LOWER JAW.
Pl. 12.
Case. Comp. Tablet. Specimen.
=J= _c_ 12 1-6
Prof. Owen has described in a 'Palæontographical' monograph the
proximal end of a mandible in which the sutures are obliterated.
But there is one specimen of a young right ramus showing the inner
and under part of the mandible to be the surangular bone which
unites with the angular or outer bone by a longitudinal and vertical
suture traversing on the inner side the great upper groove; and on
the surangular the greater part of the articular bone rests. The
articulation is strong and double, consisting of a deep transverse
hollow, bounded by a strong over-locking ridge in front and a slight
ridge behind; and this area is divided into two tapering furrows by
a strong oblique and rounded crest, which passes from behind inward
and forward. Just behind the articulation is a ?pneumatic aperture,
and then the upper surface tapers to the under surface, forming a
heel, of which one specimen measuring an inch deep on the inside of
the articulation has 3/4 of an inch still left and is more than 1/4
inch thick at the fracture. In a specimen belonging to the Rev. T. G.
Bonney the outside of the jaw is 11/16 of an inch deep, and under the
articulation 5/16 of an inch deep. The articular area is 3/4 of an inch
wide and 6/16 of an inch long.
Seven specimens indicate four species.
The proximal end of the lower jaw is entirely Avian. The pneumatic
aperture, as in birds, is placed behind the articulation, which is
shaped as in many birds. Commonly in Ornithosaurians the bones are
anchylosed and all trace of sutures obliterated, as in most birds. In
the Goose, however, the six elements of each side are sometimes as
readily separated as in reptiles. And in some Pterodactyles the bones
separate.
THE DENTARY BONE
Pl. 12.
The dentary bone consists of a single piece, as in birds and
chelonians; and differs from both in being provided with teeth. It is
described under the species O. machærorhynchus, page 113.
------------
THE TEETH.
Pl. 12.
Case. Comp. Tablet. Specimen.
=J= _c_ 17 1-39
The first three teeth are usually larger than those which are
placed behind them, in this respect rather resembling some fossil
reptiles than Dolphins, and presenting a character like that seen
in the Dimorphodon. They are placed in oblique oval sockets. They
have a single fang like Cetaceans, Edentates, Reptiles, and like
the premaxillary teeth of Mammals. Cambridge specimens of jaws are
not sufficiently perfect to show whether the teeth are limited
to the premaxillary bone; but this appears to be the case in
_Pterodactylus crassirostris_ (Goldf.), and probably in _Ornithocheirus
compressirostris_ (Owen), [_Palæontographical Society_, 1851, Pl. 27],
and is so regarded by Professor Owen in his later writings. Yet the
significance of this fact seems to have been forgotten, and Cuvier's
dictum about their teeth still has influence. He says, "The teeth, by
which the examination of an animal ought always to be commenced, here
present nothing equivocal. They are all simple, conical, and nearly
alike, as in the crocodiles, monitors, and other lizards." But, on the
one hand, the Dolphins demonstrate that a mammal might have similar
teeth even in the maxillary bone; and, on the other hand, since teeth
in the premaxillary bone always are single-fanged, and commonly have
a simple sub-conical crown, there is absolutely no evidence in the
teeth of the affinities of the animal, which, so far as this portion
of its economy went, might as well have been a fish or a mammal as
anything else. In the succession there is nothing very distinctive.
In the Crocodile one tooth comes up under another, as is commonly
the case with mammals; and in mammals the fangs of the old teeth are
often partially absorbed so that the teeth drop out into the mouth. In
the Pterodactyle the new teeth came up on the inner side, as in the
Ichthyosauria--a tribe of animals as singular in their affinities as
the Ornithosauria. Occasionally specimens show a small furrow on the
inner side of the fang, indicating absorption, but there is nothing
to show how many times the teeth were renewed: in the Dolphins there
is but one set, and in Crocodiles the teeth are replaced many times.
In form and size the teeth are very variable. They are directed
obliquely forward, and are curved backward and inward. They taper
in an elongate cone, compressed from side to side, flattened on the
outside, moderately convex on the inside; rarely the sides meet in a
ridge after the plan of Pliosaurus, Megalosaurus, Dakosaurus, &c.;
more frequently the lateral margins round into each other. Usually
the enamel is quite smooth, sometimes, as in No. 1, it is finely
striated and wrinkled. Some teeth are nearly circular and some quite
straight. The ovate fang contracts below, conically, and is closed,
leaving a long hollow pulp-cavity in its interior. Nos. 9, 10 show the
marks of the successional teeth on their inner sides. No. 11 appears
to have had the crown slightly worn at the tip during the animal's
lifetime. In transverse section of the crown the tooth structure
resembles Ichthyosaurus, Cetaceans, and Bats. The dentine is filled
with calciferous tubes which radiate as in Ichthyosaurus, and towards
the centre of the tooth are seen in transverse section to present
many angles, almost like radiated corpuscles. They are separated by
interspaces of their own width, and run towards the circumference,
sometimes straight and sometimes wavy, parallel to each other. They
send off branches usually at right angles which anastomose with the
adjoining tubes. The dentine is in concentric layers, and shows layers
of sub-circular cells as in the teeth of Mammals. The enamel is a thin
transparent layer with fewer and finer tubes than the dentine.
------------
A SUMMING UP.
The story of the structure of the Ornithosaurians of the Cambridge
Greensand has now been told, and it only remains to gather up the
threads of their affinities and determine the Pterodactyle's place
in nature. But before doing so, so various in importance are the
characters enumerated, that I would first offer a few remarks on the
classificational value of characters among the Reptilia, with which
Pterodactyles have been most commonly grouped.
The naturalist who only examines organisms now living on the earth,
symbolizes to himself, by the term Reptile, a definite sum of
characters, with definite subdivisions and subordinate grouping, to
which the extinct types of life extricated from the rocks cannot
entirely be adapted. When the fragmentary, and often isolated or
ill-associated, bones of fossilized animals are contrasted with
corresponding bones in the skeletons of Serpents, Crocodiles, Lizards
and Turtles, not infrequently it is found that the characters
attributed to different Ordinal groups are interlaced in a single
individual with a type of organization peculiar to itself, and
important as are the modifications of existing orders. These characters
occasionally are grouped with others which in living animals had been
deemed characteristic of Fishes, Amphibia, Birds, and Mammals.
The Reptilia of the Palæontologist is therefore a vast and provisional
group, ever acquiring new characters, to which no diagnosis can be
applied. And although certain empirical characters have served to
allocate the specimens in their several orders, in general with
sufficient accuracy, yet from the imperfect preservation of some of the
remains, or the imperfect extent to which their structures are known,
and the want of recognised canons by which to measure their relative
values, it has not been possible to discuss the relations of the
several orders to each other or with the larger groups on which some of
them impinge.
Classifications represent more or less faithfully the gradational
increase in the sum of the characters of an organism, as well as the
increase in importance that those character severally attain. Thus
gathering, so far as may be, from the chaos of individuals, _a common
plan of structures_ on which the genus, order, or class is moulded
from a less specialized group of organs. The fundamental structures
of a vertebrate animal, so far as their persistent importance can be
measured, are, those connected with
I. Perpetuating the race.
II. Construction of the brain.
III. Circulation and oxidation of the blood.
IV. Locomotion, i.e. skeleton, muscles, &c.
And these characteristics are for the most part so interlinked, that
it becomes difficult to assign to one order of animals a relative
superiority over another order; since when a single set of organs is
prominently developed in one group it often happens that another set of
organs has a like pre-eminence in an allied group. Thus among reptiles
it might be considered that
_Crocodiles_ have the best hearts, and _Turtles_ the best lungs.