I have not been able to obtain any skull of this species, which,
according to Cuvier's account and figures ('Oss. Fossiles,' t. ix. p.
102), resembles _C. Americanus_ in the great convexity of its nasal
region, but differs from it in the greater breadth of the skull, and in
the strong converging preorbital ridges, which appear to be limited to
the lachrymal bones. If the figures are to be I trusted, however, there
are other very important distinctive characters about the cranium of
this species; for Cuvier's, fig. 2, pl. 331, which gives a view of the
palate, shows the premaxillo-maxillary suture forming a nearly straight
transverse line.
* * * * *
There remain several species of _Crocodilus_ whose skulls I have not
been able to examine, and of which no sufficient descriptions exist. Of
these, (7.) _C. galeatus_ and (8.) _C. Gravesii_ (_planirostris_) would
appear to be very distinct forms. (9.) _C. marginatus_ is considered by
Duméril and Bibron to be only a variety of _C. vulgaris_; and they take
the same view of (10.) _Crocodilus suchus_. Professor Owen, however, has
figured the cranium of an Egyptian mummy under this name ('Monograph on
the Reptilia of the London Clay,' Pal. Soc., 1850). In the under-view
of this skull (tab. i. fig. 2), the junction of the premaxilla and the
maxilla in the palate seems to be broken away; but on the left side, the
palatine process of the maxilla is entire, as far as the level of the
anterior margin of the sixth tooth, and there is not a trace of a suture
behind this point. Are there, then, two or more species of Crocodile in
Egypt, as Geoffroy St.-Hilaire supposed?
With regard to the distribution of the species of _Crocodilus_, _C.
vulgaris_, _C. marginatus_, and _C. suchus_(?) appear to be exclusively
African; all the crocodiles from other parts of the Eastern hemisphere,
which I have met with, belong, as I have stated above, either to _C.
biporcatus_ or _C. bombifrons_, both of which species are found in
the Ganges. _Crocodilus galeatus_ appears to be peculiar to Siam.
_Crocodilus Americanus_ and _C. rhombifer_ are undoubtedly American. _C.
Journei_ has been supposed to be African; but such positive evidence as
exists tends rather to prove it to be an American species. Thus Bory de
St. Vincent states that the Bordeaux specimen is "suspected to have come
from America;" and, as I have said, the skull in the British Museum is
labelled "from the Orinoko."
_Crocodilus Gravesii_ (_planirostris_) is supposed by Bory de St.
Vincent to have been brought from the Congo; but its real origin is not
known.
Genus 5. MECISTOPS.
The cranium is elongated, and the snout slender and Gavial-like. There
are eighteen slender and subequal teeth above, and fifteen below, on
each side. The mandibular symphysis extends back to the level of the
seventh tooth. The cervical scutes are arranged in two transverse rows,
each of which contains two scutes; and there is no space left between
the posterior row and the tergal series.
This excellent genus, as established by Dr. Gray, includes Cuvier's
_Crocodilus cataphractus_ (which Dr. Gray considers to be the young of
a species whose full-grown form was discovered by Mr. Bennett in West
Africa), _Crocodilus Journei_ and _Crocodilus Schlegelii_. As I have
endeavoured to show, however, _C. Journei_ is a true crocodile; and, as
I shall point out below, Müller and Schlegel have satisfactorily proved
_C. Schlegelii_ to be a Gavial. Consequently _Mecistops_ is at present
represented by only one species, which must be called _M. cataphractus_
if _M. Bennettii_ of Gray is really the adult of the form which Cuvier
described.
* * * * *
III. In the family of the GAVIALIDÆ, the snout is always very long and
slender; the teeth are for the most part slender, sharp-edged, and
subequal. The two anterior mandibular teeth pass into grooves, one of
which lies on each side of a beak-like prominence of the premaxillæ,
which carries the two anterior upper teeth. The canines are received
into grooves. The mandibular symphysis extends back to at least the
fourteenth tooth, and is partly formed by the junction of the splenial
bones. The premaxillo-maxillary suture is always strongly convex
backwards. The posterior nares are situated more forward than in the
_Crocodili_. The temporal fossæ are large. The feet are strongly webbed.
The dorsal scutes are not articulated; and there are no ventral scutes.