Part 2

The rib of the ninth vertebra is terminated by a single long and slender semicartilaginous process which does not unite with the sternum. Each of the vertebral ribs from the tenth to the seventeenth vertebræ inclusively, on the other hand, is united with the sternum, or its continuation, by two such semicartilaginous costal elements, which may be respectively termed sternal and lateral. The sternal elements of the ribs of the tenth and eleventh vertebræ are united with the sternum proper; those of the next five vertebræ are connected with its median backward prolongation, while those of the seventeenth vertebra are attached to the processes into which this prolongation divides posteriorly.

The sternal costal elements are very broad and flat, and though the lateral ones are less so, they are wide and expanded. The lateral costal pieces of the eleventh to the sixteenth vertebræ inclusively, give attachment to very large and flat, triangular, _processus uncinati_. Those of the twelfth are 3-3/4 inches long and 1-3/8 inch wide at their widest part. The transverse processes of the twentieth vertebra bear rudimentary ribs. The centrum of the thirteenth vertebra is 1-3/4 inch long, and the vertebra is 3-3/4 inches high from the lower edge of the centrum to the summit of the neural spine. The centra of the vertebræ retain nearly the same length to the twentieth caudal; but behind this vertebra they are shorter, as are the anterior dorsal vertebræ. The first caudal vertebra is provided with two styliform bones, which represent the chevron bones of the other caudal vertebræ, but are not united below.

The dorsal scutes have the arrangement which his often been described. They are separated (except perhaps the median rows) by integumentary spaces, neither overlapping nor uniting by sutures; and there are no ventral scutes.

Among the osteological characters which have been detailed, the peculiarities of the tergal armour, the proportions of the skull, combined with the characters of the ridges upon its surface, and the form of the premaxillo-maxillary suture amply suffice to diagnose this species. Even in the small skull, only 5-1/2 inches long, lent to me by Dr. Gray, the characteristic features of the species are well exhibited, although age appears to give rise to many differences. Thus the posterior margin of the external nostrils does not extend so far back as in the adult, and the facial is smaller in proportion to the syncipital region, whose anterior and posterior transverse dimensions are very nearly equal. The orbits are proportionally larger, the interorbital space more excavated; and the outer straight margins of the supra-temporal fossæ are parallel with the longitudinal axis of the skull. Still more important differences are visible on the palatine face of the skull. The premaxillo-maxillary suture reaches back, indeed, to the line of the seventh tooth; but it forms an even curve whose summit is in the middle line. The aperture of the posterior nares, again, has a totally different form from that which it assumes in the adult. It is somewhat heart-shaped, with its apex forwards, measures 1/4 inch long by 3/16ths at broadest, and looks altogether downwards, while its anterior margin is situated far more forward in the palate than that of the adult.

2. _Crocodilus biporcatus._

This, the best-known Crocodile, is a very well-marked species, characterized (beside the peculiarities of its dermal armour) by a comparatively slender skull, similar in shape to that of _C. vulgaris_, and, like it, without any sudden enlargement immediately behind the canine groove; and by the strong ridge which arises on each lachrymal bone close to the anterior edge of the orbit, and is continued forwards on to the line of junction of the nasal and maxillary bones, so that the naso-maxillary suture traverses the axis of the ridge, and then CURVES outwards, descending towards the alveolus of the tenth tooth. The premaxillo-maxillary suture is W-shaped; and its salient angles reach backwards even to the level of the posterior margin of the seventh alveolus.

3. _Crocodilus Americanus_ (_acutus_, Cuv.)

has the slenderness of snout (even more marked) and the form of the premaxillo-maxillary suture of the preceding species; but it is at once distinguished from this and all other Crocodiles (except _C. rhombifer_) by the marked longitudinal and transverse convexity of the middle of the face, which gives the profile a totally different aspect from that of the other species, which are flat or concave in this region.

4. _Crocodilus Journei_

is another unmistakeably distinct and very remarkable species. The descriptions and figures given by Graves, Bory de St. Vincent, and Duméril and Bibron, of the unique specimen of this Crocodile to the Bordeaux Museum, would alone have compelled me to differ entirely from the view taken by Dr. Gray of the affinities of this species. These observers agree in stating that _Crocodilus Journei_ has six cervical scutes, arranged as in the other Crocodiles, and, as Graves says, "separated by an interval of four inches" from the commencement of the tergal scutes, whence it is obviously impossible that it can be a _Mecistops_. But, in addition to this, I had the good fortune to find, among the recent additions to that excellent osteological collection which Dr. Gray has gradually formed at the British Museum, the skull of a Crocodile obtained from a dealer in Paris, and labelled by him "Croc. de l'Orinoke." I at first imagined this Crocodile to be a _Mecistops_; but on careful investigation it turned out to be no other than the skull of a _Crocodilus Journei_, somewhat larger than the Bordeaux specimen, but, as the subjoined measurements will prove, agreeing with it in all its proportions:--

Inches.

Length from end of snout to end of ossa quadrata 22-1/2 Breadth between outer margins of ossa quadrata 9-3/4 ---- at the level of the anterior margins of the orbits 5-1/2 ---- at the tenth tooth 3-1/2 ---- at the end of the snout 2-3/4 ---- of the interorbital space 1-3/4 Length of mandibular symphysis 5

Now Duméril and Bibron expressly state that the length of the head of _C. Journei_ equals 2-1/2 times its greatest transverse diameter, that the width of the jaws at the anterior margins of the orbit equals one-fourth the length of the head, and that at the tenth tooth it equals one-sixth the length of the head; and these are as nearly as possible, it will be observed, the relations of the same dimensions in the above list.

In the specimen in the British Museum there are eighteen teeth on each side above, and fifteen below. The Bordeaux specimen is stated to have the same dental formula, except that there are sixteen teeth in the left ramus of the mandible. The fourth and tenth maxillary teeth are stated by Graves to be as large again as the others; and the corresponding alveoli have these proportions to one another in the British Museum specimen. In fact, there can be no doubt that this skull is that of a true _Crocodilus Journei_.

But its general characters at once prove the close affinity of _C. Journei_ with the other true Crocodiles, from which it differs only in its elongated and gradually tapering skull, and in the more backward extension of the mandibular symphysis[4], which attains the level of the posterior margin of the sixth tooth.

In this character, and in the extreme slenderness of the snout, there is doubtless an approximation to _Mecistops_; but _Crocodilus Journei_ is sharply separated from that genus by the characters of its teeth, and by those of its dermal armour.

[4] The greater proportional length of the symphysis is noted by Duméril and Bibron.

5. _Crocodilus bombifrons_ (_palustris?_).

All the species of _Crocodilus_ which I have hitherto mentioned have, in common, the backward curvature of the premaxillo-maxillary suture to the level of the seventh tooth. But there is a species of Crocodile, about whose proper specific name I am by no means clear, in which this suture passes straight across the palate, or may even be a little convex forwards.

And not only do the skulls of this species exhibit this approximation to those of the _Alligatoridæ_, but they resemble them still further in their rounded snouts, their great width immediately behind the canine groove, and in the fact that, in young specimens, one or the other canine may be received into a pit instead of into a groove[5].

In the Hunterian Collection there are seven skulls, varying in length from 5-1/4 inches up to 16 inches, in none of which does the crown of the premaxillo-maxillary suture extend beyond a line joining the sixth pair of teeth. In all there are two short ridges (convergent in young specimens, nearly parallel in old ones) upon the lachrymal bones, which end before reaching the anterior limits of those bones. They all have an oblique ridge on the upper jaw above the tenth tooth; and the snout attains the width which it has opposite this tooth immediately behind the canine groove. In the British Museum there are five middle-sized skulls with the same characters; but two of these have a pit on one side of the upper jaw, and a groove on the other, and one has something between a pit and a groove on each side.

Dr. Gray, has in his 'Catalogue[6],' mentioned the peculiar transverse disposition of the premaxillo-maxillary suture in his _Crocodilus bombifrons_; and on examining the two crania thus named in the British Museum collection, one of which is 20 and the other 21 inches long, I can discover no distinguishing character between them and those already described. There can be no doubt then, I think, that these constant and well-marked characters, exhibited by fourteen skulls which vary in length from 5-1/4 to 21 inches, prove the existence of a distinct species of Crocodile, which I would provisionally term _bombifrons_.

[5] In a skull of this species 14-1/2 inches long, in the British Museum, the vomers are completely excluded from the palate, and their anterior ends do not extend for an eighth of an inch beyond the palatine part of the palato-maxillary suture, which lies on a level with the anterior margin of the twelfth alveolus. Each vomer is 2-3/8 inches long, and presents the same general form as that of _Jacare_; only the anterior division is but a very small, flat and thin plate, not a quarter of an inch long. The boundary of the median nares is formed in equal proportions by the vomer and the palatine, and is opposite the fourteenth tooth. The hinder end of the vomer articulates with the end of the descending process of the prefrontal.

[6] 'Catalogue of the Tortoises, Crocodiles, and Amphisbænians in the Collection of the British Museum,' 1844, p. 59.

I believe that this species has been constantly confounded with _biporcatus_, from which it may be at once distinguished by the direction of the premaxillo-maxillary suture, and by the shape of the snout behind the canine groove. I have found these distinctions to hold good at all ages; but the last-mentioned difference is far more marked in middle-aged than in either young or old specimens.

All the skulls named _Crocodilus palustris_ which I have seen are referable either to _C. biporcatus_ or to _C. bombifrons_. With respect to the _C. palustris_ of Lesson and Duméril and Bibron, the latter authors consider it to be only a variety of _C. vulgaris_. Their description would, however, apply very well to _C. bombifrons_, as I have defined it above; and they expressly state ('Erp. Générale,' t. iii. p. 113) that all their specimens (twelve in number and varying in length from 30 centimetres to more than 3 metres) came from the East Indies or the Seychelle Islands. Now, Duméril and Bibron enumerate only three Asiatic Crocodiles--_C. biporcatus_, _C. palustris_, and _C. galeatus_, the last of which was only known to them by description; so that all the numerous Asiatic crocodiles which passed through their hands belonged either to _C. biporcatus_ or _C. palustris_. On the other hand, all the skulls of crocodiles from Asia which I have met with (amounting to at least twenty) are either those of _C. biporcatus_ or of the species which I have called _bombifrons_; so that I suspect the latter title will turn out to be a synonym of _palustris_.

6. _Crocodilus rhombifer._

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.

I distinguish two genera in this family, _Rhynchosuchus_ and _Gavialis_.

Genus 6. RHYNCHOSUCHUS.

There are twenty teeth above, and eighteen or nineteen below, on each side; the mandibular symphysis extends to the fifteenth tooth. The posterior teeth of the upper jaw, and almost all those of the lower jaw, are received into interdental pits; the orbital margins are not raised; and the premaxillæ are hardly at all expanded. The premaxillo-maxillary suture does not reach the third tooth behind the notch.

I propose the name _Rhynchosuchus_ to indicate that generic type which is at present represented by the solitary species called by Müller and Schlegel _Crocodilus_ (_Gavialis_) _Schlegelii_, and admirably described and figured by them in their essay, 'Over de Krokodilen van der Indischen Archipel,' in the 'Verhandelingen over de natuurlijke Gesch. der Nederl. overzee. Bezittingen,' 1839-1844. Under the title _Crocodilus_ (_Gavialis_) _Schlegelii_ (p. 18), they say--"The Gavial from Borneo, when compared with the Indian one, is principally distinguished by the following characters:--

"1. By its stronger form and better developed limbs.

2. By its much less slender head and snout, which last does not narrow so suddenly in front of the eyes as in _G. Gangeticus_.

3. By the smaller number of teeth, of which there are twenty above and eighteen below on each side, while _G. Gangeticus_ has 28/26 or 27/25; furthermore, the teeth are stouter, less curved, and less sharp, and are disposed more perpendicularly, and the ninth tooth of the upper jaw (reckoning from the front) is considerably larger and stronger than the others; whence it follows that, just as in the true Crocodiles, the snout at the level of this tooth exhibits a lateral projection.

4. By the shorter symphysis of the under jaw.

5. By the absence of the swollen nasal prominence (neusklep), which characterizes the Gangetic Gavial.

6. By the less expanded form of the tabular upper surface of the hinder part of the skull.

7. By the very slight production of the edges of the orbit.

8. By the large eyes.

9. By the presence of a number of small nuchal shields, while _G. Gangeticus_ has but one pair.

10. By the strongly developed keels of the dorsal scutes.

11. By the much larger scales on the under parts and on the legs of the animal.

12. By the different colours with which it is variegated."

* * * * *

These authors further point out that the vomers appear for a small space in the posterior part of the palate, that the opercular or splenial bones join in the symphysis of the lower jaw, and that the cervical and dorsal scutes form one continuous shield; and they represent the two anterior mandibular teeth passing in grooves on either side of the end of the premaxilla. In fact, they fully and completely establish the fact that their new species belongs to the _Longirostres_ of Cuvier, or to the Gavials of later writers.

Under these circumstances, it is somewhat surprising to find the deliberate conclusions of these careful investigators set aside in the following brief passage:--

"This Bornean species (_C. Schlegelii_) was, in fact, originally described as a new species of Gavial; but the nasal bones, as in the fossil from Sheppey, figured in t. ii. 15, extend to the hinder border of the external nostril."--_Owen_, _Fossil Reptilia of the London Clay, Crocodilia_, p. 15: 1850.

Müller and Schlegel give remarkably clear and beautiful figures of the skull of their Gavial; and these show at once that the nasal bones do not "reach the hinder border of the external nostril," but meet the premaxillaries at a point very distant from that border, viz. opposite the ninth tooth. Even did the nasal bones reach the posterior boundary of the nostril, such a character would not outweigh those derived from the relations and number of the teeth, the structure and extent of the mandibular symphysis, and the disposition of the dermal scutes,--all of which are so clearly and definitely set forth by Müller and Schlegel, that it seems difficult to understand how any one who had consulted the original memoir could have overlooked them.

It was possible, however, that Müller and Schlegel, notwithstanding their great opportunities, might have erred in their statements; and I therefore gladly seized the opportunity of testing their description by comparing it with an authentic skull of the species in question, from New Guinea, in the collection of the British Museum.

I have found the statement of Müller and Schlegel minutely accurate in almost all points; and there cannot be the slightest doubt, not only that the Schlegelian crocodile is one of the _Gavialidæ_, but that it forms a distinct generic type in that family, as different from _Gavialis_ as _Caiman_ is from _Jacare_, or _Mecistops_ from _Crocodilus_.

* * * * *

The following are the most important measurements of the skull of _Rhynchosuchus Schlegelii_ in the British Museum collection:--

Inches.

Length from the end of the premaxilla to that of os quadratum 23 Breadth from outer edge of one os quadratum to that of the other 8-3/4 Breadth across the face in front of the orbits 4 " at the 9th tooth 2 " at the 5th tooth 1-1/2 " at the 3rd tooth 1-3/4 " of the beak-like curved process which carries the two anterior teeth 1 Mean width of lower jaw from symphysis to extremity 1-5/8 Length 12 No tooth measures transversely more than 3/16

The face is very smooth; but a slight longitudinal groove runs down on each side from the anterior margin of the orbit for about two inches. Anteriorly to this point the snout retains a nearly even diameter as far as the ninth tooth, in front of which it suddenly narrows a little, retaining nearly the same dimensions to the fourth tooth, where it widens a very little, and then suddenly narrows to the terminal beak. The lower jaw does not expand at all at its extremity. The nasals join the premaxillaries opposite the ninth tooth, and the splenial bones, in the lower jaw, end opposite the tenth mandibular tooth, as the figures of Müller and Schlegel show. The vomers appear between the inner edges of the palatines posteriorly, as a thin bony band 1-3/8 inch long by 1/8 inch wide, which tapers at each end and is divided by a longitudinal suture. The ninth tooth of the upper jaw is stronger than the rest.