304 ON THE DERMAL ARMOUR OF JACARE AND CAIMAN 
teeth on each side of the upper jaw pass straight down outside 
the lower jaw. In the Gangetic Gavial the relations of the tecth 
of the two jaws appear to me, as I shall state below, to be very 
different. 
Rhynchosuchus Schlegelit inhabits the inland lakes of Borneo, and 
is found in New Guinea. 
Genus 7. GAVIALIS. 
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 teeth 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 premaxille 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 Gavzals 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-manillary 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 developed 
within the substance of the dermis. To the former I shall apply the 
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 Cazman and /acare, are there any scutes in 
the ventral region. 
