18 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 



of the Geckos. Its habits are singular. It lives on the dry sand of the beach, 

 at some distance from the vegetation, and the colour of the body much resembles 

 that of the sand. When frightened it depresses its body, stretches out its 

 legs, and closing its eyes tries to escape detection. If pursued it buries itself 

 with great quickness in the sand ; but as its legs are short, it cannot run very 

 swiftly." 



Proctotretus pectinatus. 



Plate IX.— Fig. 2. 



Capite squamis subccqualibus, rhomhoideis, imhricatis, carinatis iecto. 



Proctotretus pectinatus, Bibr. Hist. Kept. IV. p. 292. 



Habitat, Patagonia. 



Description. — The scales of the head are narrow, closely imbricated, strongly but not acutely 

 carinated, and the anterior ones arranged in somewhat of a radiating direction from the muzzle. 

 There is but a single series of scales between those of the upper lip and the orbit, and these, 

 together with all the scales about the head, partake of the carinated and elongated character 

 already described. A single strong triangular scale and two smaller ones are placed on the 

 anterior margin of the ear, which is narrow, oval and reniform. The scales of the temples and 

 sides of the neck are rhomboidal, acute, carinated and imbricated. There is a longitudinal 

 fold on each side of the neck and a transverse one anterior to the shoulder, behind which is a 

 deep depression. The scales of the back and side are prominently and acutely carinated, those 

 of the central line being rather more prominent than the others ; and above this there is on 

 each side a marked longitudinal lateral crest extending from beneath the eyes to the base of 

 the tail. The scales constituting these crests are very prominent, narrow and acutely carinated. 

 The scales of the belly are also imbricated and rhomboidal, but fiat; those of the under surface 

 of the hands and feet arc carinated ; and those of the toes have three carinae. The body is 

 somewhat depressed as is the tail at its commencement, becoming more rounded and rather 

 abruptly smaller at some distance from its origin. The fore-foot reaches to about two-thirds of 

 the distance from the shoulder to the side, and the hinder extremity thus placed extends to the 

 shoulder. 



The colours of this most elegant of all the species of the genus are very beautiful. " This 

 is the most beautiful lizard," says Mr. Darwin, " I have ever seen ; the back has three rows of 

 regular oblong marks of a rich brown, the other scales symmetrically coloured either ash or 

 light brown; many of them of a bright emerald green; beneath pearly, with semilunar spots of 

 brilliant orange on the throat." I find in the specimens I have examined that the pectinated 

 lateral crests are white, and the brown oblong marks of the back are bordered with a similar 

 colour. There are always three white transverse lines across the head. 



