226 



Key to the Indo-Australian species. 



^. Head very small; neck very slender. 



I. Two superposed anterior temporals. 



a. Praefrontals separated by the frontal \. H. frontalis p. 227. 



b. Praefrontals in contact 2. H. nigrocinctus p. 227. 



11. A single anterior temporal. 



a. Frontal as long as its distance from the rostral. 



1. Scales in 29^ — 37 rows round the body. 



X 29 — 33 scales round body ; ventrals 



225 — 298 Z- ^- gJ'acilis p. 22S. 



XX 37 scales round body; ventrals 298 — 321. 4. H. flowerl p. 229. 



2. Scales in 40 — 50 rows round body. 



aa. 31 — 40 scales round the neck; 40 — 50 



round the body; ventrals 310 — 438 . . ^. H. diadcma p. 229. 

 bb. 25 — 31 scales round the neck; 40 — 48 



round the body; ventrals 345 — 500. . . 6. H. fasciatus p. 230. 

 cc. 30 scales round the neck; 42 round the 



body; ventrals 416 "]. H. brookct p. 230. 



/^ Frontal shorter than its distance from the rostral. 8. H. torqiiatus p. 231. 

 B. Head moderately small ; neck not very slender. 

 I. Anterior ventrals three or four times as broad 

 as the last row of scales <^. H. viperinus p. 231. 



II. Anterior ventrals not more than twice as broad 

 as the last row of scales. 



a. One anterior temporal. 



1. 19 — 21 scales round the body 10. H. jerdoni p. 232. 



2. Scales round the body in more than 21 rows. 



t Ventrals 159 \\. H. mcrtoni p. 233. 



tt Ventrals 270 — 354. 



ca. Scales round body in 45 rows . . . . 12, H. polyodonhts p. 233. 

 bb. Scales round body in 32 — 40 rows. 



X Head yellow ^Z- ^- brugmansi p. 233. 



XX Head black with a curved yellow 



marking \\. H. spiralis p. 234. 



ttt Ventrals 372 — 400 15. //. gra/idis p. 235. 



b. Two or three superposed anterior temporals. 

 I. Scales round body in 34 — 50 rows; ventrals 

 squarish. 



X Second pair of chin-shields, if distinct, 

 separated by several scales. 



fffl. One postocular 16. H. hyhridiis p. 235. 



/V'. Two or three postoculars 17. ^. ornaliis p. 236. 



