REPTILES. 7 



small interrupted fascia of the same colour extends from the shoulder to the thigh. The 

 belly is of au uniform dirty white. 



This species approaches considerably to Pr. cyanogaster in general form and habit, and in 

 many of its characters ; but it may be at once distinguished from it not only by its colouring, 

 but by the absence of even the slightest appearance of a carina on any of the scales of the 

 temples or of the sides of the neck. 



DIMENSIONS. 



Inches. Lines. 



Length of the head 6 



of the body 1 6 



of the tail 3 4 



Total length 5 6 



Length of anterior extremity 7 



of posterior extremity 1 1 



Found by Mr. Darwin at Port Desire, in Patagonia. 



Proctotretus tenuis. 

 Plate III.— Fig. 2. 



Capite squamis lesvibus, non imbricatis ; auribus magnis, margiue anteriore sub- 

 tuberculato; serie unica squamarum supralabialium ; temporibus squamis rotun- 

 datis, imbricatis ; collo granuloso ; squamis dorsi parvis, obtusis, carinis minimis ; 

 squamis lateralibus exiguis, non imbricatis; facie posteriore femorum omnino 

 granulosa. 



Proctotretus tenuis, Bibr. 1. c. p. 279. 



Description.- General form slender: head rather short and obtuse, covered with flattened smooth 

 scales; anterior margin of the ears with one or more slight tubercles ; temples covered with 

 rounded imbricated scales, some of which are slightly carinated; sides of the neck, and 

 above the shoulders granular; scales of the back small, slightly carinated, obtuse; those of 

 the sides very small, very little imbricated ; those of the belly small and smooth. The 

 posterior surface of the thighs has no patch of imbricated scales, but is wholly granular. 



The colour of the two specimens brought home by Mr. Darwin is so much obliterated, 

 that I am obliged to have recourse to the account given by Bibron of the colour and markings 

 of this species: — "Les deux sexes du Proctotrete svelte n'ont pas le meme mode de coloration. 

 Ni l'un ni 1'autre ne portent, de chaque cote du dos, une bande longitudinale verte ou jaunatre 

 comme cela s'observe dans Pespece precedente, (Pr. pictus.) 



" Le male a le dessus de la tete nuance de brun et de fauve, ou bien ponctue de jaune 

 et de noiratre. La region cervicale est, ainsi que le dos, vermiculee de noir sur un fond brun, 



