CHARACTEES OF EECENT CEOCODILIA. 21 



nor do the posterior margins of those in each transverse row overlap 

 the anterior margins of the succeeding row. At any rate, there is 

 no flat, bevelled, articular facet on the outer surface of the anterior 

 margin of a scute, for articulation wdth the inner surface of the 

 posterior margin of its predecessor. In the genera Caiman and 

 Jacare, however, the lateral edges of all the scutes of the dorsal 

 and ventral shields are united by serrated sutures ; and the anterior 

 end of the outer face of each is provided with a well-marked smooth 

 facet, which is overlapped by the smooth under-surface of the 

 scute in front of it. 



I first noticed the remarkable structure of the dermal armour 

 of these Alligatoridcd'm. the skin of a Jacare {sp. incerta), wanting 

 the end of the tail, but which must have belonged to an animal 

 between five and six feet in length. It had long been in my pos- 

 session ; but I had never before had occasion to study its cha- 

 racters minutely. 



The horny scales, which had the appearance of thin tortoise- 

 shell, could be readily peeled ofi" (especially by the aid of a little 

 caustic potash) ; and then the white surface of the subjacent 

 bony scute upon which they were modelled came into view. It 

 is to be understood, however, that the inner surface of the scale 

 corresponded only in its general form with the outer surface of 

 the scute ; for it did not dip into the pits with which the latter 

 is sculptured. These are in fact filled by the dry dermis which 

 extends over and encloses the scute, a very thin layer (bearing the 

 rete mucosum) being interposed between it and the scale ; so that 

 the pitted sculpture does not come out well until the scutes have 

 been boiled. 



The dorsal scutes are both carinated and angulated. By the 

 application of the former term, I mean to indicate that, along a 

 median or submedian longitudinal line, their substance is more 

 or less elevated, so as, in many cases, to form a very prominent 

 crest. This crest always subsides before it reaches the anterior 

 margin of the scute, though it may extend beyond the posterior 

 margin. Its highest point is alw^ays behind the centre of the 

 scute, and is devoid of sculpture. The sculpture however seems 

 to radiate from this point, inasmuch as it consists, on the greater 

 part of the scute, of distinct pits, which, are usually round towards 

 the centre, but towards the periphery become ovals with their 

 long axes directed towards the point in question. 



The smooth inner surfaces of the scute shelve towards a depres- 

 sion which corresponds with the external ridge, under which the 



