SYXOrsES AM) DESCRIPTIOXS. • 33 



Helicops. 



Witijhi; 18;!0. 



Form stout, tapering to head and tail ; head hirger than the neck, 

 broad behind, narrow forward, crown tiat; tail tapering. Eyes mod- 

 erate to small, pupil round. Teeth smooth, post maxillary larger and often 

 isolated. Head-shields eight or nine. Internasals narrow in front or 

 fused, generally in contact Avith the rostral. Nasal entire and gi-ooved, 

 or divided. \Mth or without a loreal. Commonly 1 — 2 ante, and 2 — 3 

 postorbitals, suborbitals rarely present. Scales keeled in 19 — 25 rows. 

 Anal bilid. Subcaudals in two rows. 

 Nasal divided; 



internasals 2 ; scales keeled, in 19 — 21 rows 



variabilis. 

 Nasal entire, grooved; 



internasal 1 ; scales in 19 rows, keels few allenii. 



Helicops variabilis. 



Tretanoriiinus variahilis Dum. & Bibr., 1854, Erp. Gin. VII, 349. 



Fusiform; head distinct, narrow across the nasals, broad behind, de- 

 pressed, crown flat ; tail moderate, tapering rapidly near the base. Eye 

 small, pu[)il round. Jaws nearly equal in length. Posterior maxillary 

 teeth little larger, slightly compressed. Rostral broader than high, con- 

 vex. Head-shields nine. Internasals small, irregular, subtriangular, not 

 at all or but little in contact with the rostral. Prefrontals broader in front, 

 longer than broad. Frontal pentagonal, truncate and narrower in front. 

 Nasal in two parts, the small nostril between, nearer the upper margin. 

 Loreals 2 (1 — 2), anterior smaller. Anteorbitals 2 (2 — 3), lower larger. 

 Postorbitals 2. Temporals 1+2+3. Labials S — 9, the tAvo j^receding the 

 last largest, a single one (fourth or fifth) under the eye. Infralabials 

 10 — 11, sixth largest (fifth or sixth). Submentals two pairs, posterior 

 larger. Scales keeled, lozenge-shaped, truncate, in 21 rows (19 — 21), dor- 

 sal finely striate, outer broader, nearly or quite smooth. Ventrals broad 

 142 (137—158). Anal bifid. Subcaudals 65 pairs (65—78). 



Light greyish to dark brown, edges of scales lighter; young with irreg- 

 ular indistinct blotches of darker. A light line on the outer two rows of 

 scales from the neck to the tip of the tail. Belly yellowish white, mottled 



JIkm. — VOL. ij — 3 



