22. crENOBLEPHARIS.—23. HELOCEPHALUS. 137 
rhomboidal, imbricate, smooth, largest under the neck. The ad- 
pressed hind limb reaches the neck. Digits rather short. Tail a 
little shorter than head and body, with rings of smooth scales. Four 
anal pores. Pale greyish olive above, with darker marblings enclosing 
roundish cream-coloured spots; lower surfaces uniform whitish. 
Total length.......... 105 millim, 
Gad soe aiens eee 1D 45 
Width of head........ IB 45 
Body x gus awn ayes 45, 
Fore limb............ QF sy 
Hind limb .......... 38 Cy; 
atl: Gsciexsa ecu cae ew 45 ,, 
Peru. 
aod. Arequiba, 7500 feet. W. Tegetmeier, Esq. [P.]. 
23. HELOCEPHALUS*. 
Helocephalus, Philippi, Reise Atacama, p. 167. 
Leiosaurus, part., Burmeister, Reise La Plata, ii. p. 523. 
This genus is apparently closely related to the preceding, from 
which it differs in having the infradigital lamelle bicarinate, and 
lacking the pterygoid teeth. 
Atacama and North-western La Plata. 
1. Helocephalus nigriceps. 
Helocephalus nigriceps, Phikippi, 7. c. pl. vi. fig. 1. 
Head short, covered with small smooth scales, the supraoculars 
being the smallest of all; ear-opening rather small, without denti- 
culation. 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. 
Heads” aee se eae eens 2h Sy 
Body) baad eae bao 56 Ca, 
Fore limb............ 34. Ci, 
Hind limb .......... 50, 
POU 4 gee yee acts) ain LO” 55 
Pajonal, Atacama, 10,500 feet. 
* Leiosaurus multipunctatus, Burmeister, /. c. p. 524.—Sierra de Uspallata, 
8000 feet. 
L. marmoratus, id, ibid, — Desert west of Catamarca. 
