REPTILES. 
19 
DIMENSIONS. 
Inches. Lines. 
Length of the head 0 7 
of tlie body 1 7 
of the tail 3 1 
Total length 5 5 
Length of anterior extremity 1 0 
of posterior extremity . t 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 flat, 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 j)^ctinated lateral crest, from which circumstance it has 
derived its name. 
Found by Mr. Darwin, at Bahia Blanca, and Port Desire in Patagonia. 
Genus— DIPLOLiEMUS. Bell. 
Caput breve, latum, suhtriangulare. Aures parvce, ovatee, margine leevi. Nares 
magncB, rotundcs. Collum infra transverse, ad latera longitudinalitSr pUeatum. 
Corpus suhdepressum, non cristatuni. Cauda teres, hreviuscula, Icevis. Pedes 
breves, robusti. Squamae capitis numerosce, parvce, rotundatce, non imbricatce — 
corporis atque caudae supra minimcB, Iceves, convexce, pauld imbricatce, infra Iceves, 
planes. Pori femorales et prae-anales m utroque sexii rmlli. Dentes palatini 
nidli. 
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 diflers, 
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 Bella (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, I>. Bibronii. 
