20 PBOr. HUXLEY ON THE SPECIFIC AND GENERIC 



RJiynchosKchus Schlegelii inhabits the inland lakes of Borneo, 

 and is fonnd in New Guinea. 



G-enus 7. Gayialis. 



There are twenty-seven or twenty-eight teeth in the upper, and 

 twenty-five or twenty-six in the lower jaw. The mandibular sym- 

 physis extends to the twenty-third or twenty-fourth tooth. The 

 lateral teetli of both jaws are, all but the very hindmost, directed 

 obliquely downwards (or upwards), forwards or outwards, and are 

 not received into interdental pits. The anterior margins of the 

 orbits are raised. The premaxillse and the end of the mandible 

 are greatly expanded. The premaxillo-maxillary suture reaches 

 the level of the fourth tooth behind the canine notch. 



The only true Gavialis is the well-known G. Gangeticus from the 

 East Indies. In this ' Gavial,' or ' Garrhial,' the vomers are slender 

 bones which do not extend further forwards than the level of the 

 twenty-second or twenty-first tooth, and have but a very short 

 and slender representative of the anterior flattened division of the 

 bone in Jacare ; posteriorly they extend back to the level of the 

 descending processes of the prefrontals. In a skull 25 inches 

 long the vomers have a length of about 4 inches, extending as 

 they do a little further forward than the palato-maxillary suture. 

 The median nares are opposite the twenty -fifth tooth. 



All the Crocodilia which I have enumerated are provided with 

 two perfectly distinct kinds of dermal armour, — the one consisting 

 of plates of horn, produced by a modification of the superficial 

 layer of the epidermis ; the other composed of discs of bone marked 

 by a peculiar pitted sculpture on their outer surfaces, and deve- 

 loped within the substance of the dermis. To the former I shall 

 apply tlie term "scales ;" the latter are what I have denominated 

 "scutes." 



All recent Crocodilia have both scales and scutes in the dorsal 

 region of the body, the scutes underlying, and having the same 

 general form as, the scales. In all, the ventral region of the body 

 is also covered with scales which have a very definite shape ; but 

 in no recent Crocodilian which I have examined, save those species 

 which are included in the genera Caiman and Jacare, are there 

 any scutes in the ventral region. 



Again, in the genera Alligator, Crocodilus, Mecistops, RhyncJio- 

 siichus, and Gavialis, the edges of the scutes, except those of the 

 two median longitudinal rows, are hardly ever united by sutures, 



