REPTILES. 19 



DIMENSIONS. 



Inches. Lines. 



Length of the head ? 



of the body 1 7 



ofthetail 3 1 



Total length 5 5 



Length of anterior extremity 1 



of posterior extremity 1 5 



This species, as has been observed by M. Bibron, who first described it, 

 may be at once distinguished from every other by the character of the scales of 

 the head, which, instead of lying fiat, with the edges in contact, are all of them 

 imbricated and carinated. Another obvious distinguishing character, is the 

 narrow line of prominent scales running the whole length of the body on each 

 side, forming a sort of pectinated lateral crest, from which circumstance it has 

 derived its name. 



Found by Mr. Darwin, at Bahia Blanca, and Port Desire in Patagonia. 



Genus— DIPLOL^MUS. Bell. 



Caput breve, latum, subtriangulare. Aures parvcs, ovatce, margine Icevi. Nares 

 magna, rotundce. Collum infra transverse, ad latera longitudinaliter plicatitm. 

 Corpus subdepressum, non cristatum. Cauda teres, breviuscula, Icevis. Pedes 

 breves, robusti. Squamae capitis numerosce, parvce, rotundatce, non imbricates — 

 corporis atque caudae supra minimce, Iceves, convexce, paulb imbricatce, infra laves, 

 planes. Pori femorales et pra>anales in utroque sexu nulli. Dentes palatini 

 nulli. 



The new genus which I have thus defined, resembles very closely, in most of its 

 characters, the genus Leiosaurus of Bibron ; from which, indeed, it scarcely differs, 

 excepting in the absence of palatine teeth, and in the form of the suborbitar 

 plates, which in Leiosaurus are all distinct, and of nearly equal size : whereas, in 

 the present genus, three of these are united to form one plate, resembling that in 

 Proctotretus, and some other Agamidce. In other respects the genera are very 

 closely allied ; but the existence or non-existence of palatine teeth, is a character 

 of so much importance, that it appeared to me, — and in this opinion I am supported 

 by M. Bibron, who examined the specimens with me, — that they should be con- 

 sidered as distinct. Both the genera are natives of South America. Of Leiosau- 

 rus Bellii (Bibr.) the only known specimens were presented to me by Capt. King, 

 who obtained them during his survey, from whom also I obtained specimens of 

 one of the species of the present genus, D. Bibronii. 



