12 NYXOI'SKS AND DESCRIPTIONS. 



Teeth equal, smooth ; 



anal entire ; scales in 13-17 vows, 

 vertebral series larger 



Leptognathus. 

 Posterior maxillary teeth longer, grooved ; 

 anal entire; scales in 19-27 rows, 

 vertebral series larger 



Dipsas. 

 anal divided, rarely entire ; scales in 19-23 rows, 

 dorsal series similar 



Si bon. 



Leptognathus. 



Dumiril, l.s.")2. 



Body long, more or less compressed; head subquadrangular, high, dis- 

 tinct from neck; tail medium. Eye moderate, pupil erect. Teeth equal, 

 smooth. Head-shields nine, short, broad. Rostral broad, low. With or 

 without a distinct loreal. Orbitals 1 — 2+2 — 3, suborbitals sometimes 

 present. Scales moderate, rarely keeled, in 13-17 rows, vertebral gener- 

 ally larger. Anal rarely divided. Subcaudals in two rows. 



Hab. Mexico to the Argentine Republic; India, 



Scales keeled in vertebral series, rows 15-17; 



loreal distinct fasciatus. 



Scales smooth, rows 17; 



loreal distinct dumeriffi. 



Scales smooth, rows 15; 



loreal and anteorbital fused; 



transverse bands narrow nebulatus. 



transverse bands broad dimidiatus. 



Leptognathus fasciatus. 



Tropidodii'sas fasciata, Gtkr., 1858, Cat. i 'ill. Snakes, 181. 



Slender; head oval, crown slightly flattened, muzzle broad; tail long, 

 slender. Eye large, pupil erect. Head-shields broad. Frontals bent on 

 the side. A loreal. Orbitals '1-1. Temporals 1+2. Labials 6-7, penult- 

 imate largest. Infralabials 7, fifth largest. Submentals two or three 



