14 SYNOPSES AND DESCRIPTIONS. 
LEPTOGNATHUS DIMIDIATUS. 
Giinther, 1872, Ann. & Mag. Nat. Hist., LX, 31. 
Long, slender, much compressed ; head broad, short; tail less than one 
third of the total length. Eye rather large, pupil erect. Internasals 
small. Prefrontals large, bent down on the face, entering the orbit. Outer 
edges of frontal nearly parallel. Loreal and preocular fused. Post- 
oculars two. Temporals 1+2. Submentals three pairs, anterior largest, 
crescent-shaped; middle longer than broad, posterior divergent. Labials 
eight, fifth and sixth in orbit. An azygos scale-like shield under the chin, 
surrounded by the first pair of infralabials, the mental and submentals. 
Second to sixth infralabials in contact with anterior submentals. Scales 
smooth, in 15 series, vertebral not larger. Ventrals 186. Anal entire. 
Subcaudals 98 pairs. 
Body and tail with broad black rings, separated by narrow, whitish inter- 
spaces. Twenty-five rings on the trunk, sixteen on tail; white interspaces 
subdivided by a narrow black transverse line. Upper parts of head black; 
with small, irregularly placed whitish spots, and a pair of large spots of 
the same color on the neck, forming a sort of collar. Anterior chin-shields 
black. (From Giinther.) Hab. Mexico. 
Drpsas. 
Laurent, 1768. 
Slender, elongate, compressed; head very large, distinct, depressed, 
broad behind, angles rounded, muzzle blunt; tail slender, tapering. Eye 
moderately to very large, pupil erect. Posterior maxillary teeth longer, 
grooved. Rostral broad, low. Head-shields nine, broad. Nasal divided. 
A loreal, rarely fused with orbital. One preocular. Postoculars two to 
three. Seales smooth, rarely keeled, in 19—27 rows, vertebral larger. 
Anal entire or divided. Subcaudals in two rows. Hab. Mexico to Brazil; 
Australia; Africa. 
(Himantodes.) 
DIPsAS CENCHOA. 
Conuper cencnoa Linné, 1758, Syst. Nat. Ed. X, 226. 
Dresas CeNcHOA Iitzinger, 1826, Neue Class Rept., 59. 
Very long and slender, compressed, neck and tail very small; head 
large, very broad, muzzle short, crown convex; tail near one third of the 
total. Eye large, pupil erect. Mouth deeply cleft, curved, Internasals 
