338 TEND. 
two nasals, Eyelids developed. Ear exposed. Limbs well deve- 
loped, each with five digits, the toes with a feebly denticulated 
fringe laterally, inferiorly with small squarish scales. Dorsal lepi- 
dosis composed of small scales intermixed with very large keeled 
tubercles ; ventral plates small, elongate subquadrangular, feebly 
keeled, forming regular series. A double collar fold. Femoral 
pores. Tail strongly compressed, with a double denticulated keel 
superiorly, 
Guianas and Basin of the Amazon. 
1. Dracena guianensis. 
Ada guianensis, Gray, Cat. p. 25. 
Dracena guianensis, Daud. Rept. ii. p. 423, pl. xxviii. 
Teius crocodilinus, Merr. Tent. p. 62. 
Thorictis guianensis, Wagl. Syst. Amph. p. 153. 
Teius (Ada) crocodilus, Gray, Griff. A. K. ix. Syn. p. 28. 
Thorictes draceena, Dum. § Bibr. v. p.56; Duvern. R. A., Rept. 
pl. x. bis. fig. 2. 
Head large, not depressed, subpyramidal. Nostrils opening on 
the upper surface of the snout, on the canthus rostralis; anterior 
nasals forming a long suture. Upper head shields: a pair of naso- 
frontals, three smaller prefrontals on a line, followed by several 
irregular small shields, a large frontal, a pair of frontoparietals, 
three subequal parietals on a line, four or five supraoculars ; occiput 
with numerous small shields; a row of three or four large supra- 
temporals ; two or three loreals and several small frenoorbitals; a 
row of infraorbitals; labials large, eight or nine upper and eleven 
to thirteen lower ; chin-shields, an anterior and nine or ten pairs, 
all except the anterior separated from the labials by smaller shields, 
the outer row of which is the largest; gular and mesoptychial 
seales flat, subhexagonal. Dorsal scales small, irregular, intermixed 
with irregularly arranged large oval strongly keeled tubercles. Ab- 
domiual scales small, narrow, feebly keeled, in thirty-four or thirty- 
six transverse and about forty longitudinal series. Preeanal scales 
small, irregular. Scales on the limbs small. Four or five small 
pores on each side in front of the preanal region and two or 
three under each thigh. Caudal scales narrow, feebly keeled, 
forming annuli; the dorsal tubercles are gradually modified into a 
strong double crest along the upper surface of the tail. Olive- 
brown above, flanks with more or less distinct lighter spots; the 
sutures of the labials and chin-shields black; lower surface yel- 
lowish, marbled with blackish. 
centim. centim. 
Total length ...... 83 Fore limb ........ 11:5 
Cad es ce oat is 8:5 Hind limb........ 15 
Width of head .... 5-5 DBI asa 5 tae Wat a 50 
Body ces sia es 24-5 
Guianas and Basin of the Amazon. 
