22. CXENOBLEPIIARIS. 23. HELOCEPHALUS. 137 



rhomboidal, imbrieate, smooth, largest under the neck. The ad- 

 ])re.ssed hind limb reaches the neck. Digits rather short. Tail a 

 little shorter than head and body, wiih rings of smooth scales. Four 

 anal jiores. Pale greyish olive above, with darker marblings enclosing 

 roundish cream-coloured spots ; lower surfaces uniform whitish. 



Total length 105 millim. 



Head 15 „ 



Width of head 13 „ 



Body 45 „ 



Fore limb 27 „ 



Hind limb 38 „ 



Tail 45 „ 



Peru. 



a. d". Arequiba, 7500 feet. W. Tegetmeier, Esq. [P.]. 



23. HELOCEPHALUS*. 



Helocephalus, Philip^n, Heise Atacama, p. 167. 

 Leiosauriis, part., Burmeister, Heise La Plata, ii. p. 523. 



This genus is apparently closely related to the preceding, from 

 which it differs in having the infradigital lamella) bicaiinate, and 

 lacking the pterygoid teeth. 



Atacama and North-western La Plata. 



1. Helocephalus nigriceps. 



Helocephalus nigriceps, PhUipjn, 1. c. pi. vi. tig. 1. 



Head short, covered with small smooth scales, the supraoculars 

 being the smallest of all ; ear-opening rather small, without denti- 

 cidation. Dorsal scales hexagonal, juxtaposed, smooth, forming 

 oblique lines. The adpressed hind limb does not quite reach the 

 axil. Tail nearly as long as head and body, conical, with rings of 

 small squarish smooth scales. Pale grey above, sides orange with 

 vertical black bars ; head and neck deep black ; lower surfaces 

 white, black-spotted. 



Total length 147 millim. 



Head 21 „ 



Body 56 „ 



Fore limb 34 „ 



Hind limb 50 ,, 



Tail 70 



J5 



Pajonal, Atacama, 10,500 feet. 



* Leiosaurun mulfipHnctafu.", I'.unnoister, /. c. p. .")'24. — Sierr.-i de U.'<pallata, 

 8000 feet. 



L. 77iarmoratus, id. ibid. — Desert west of Ciilauiarca. 



