502 SNAKES OF CEYLON. 



Breeding. — -All whose habits are known are viviparous, 

 except Causus rhombeatus, Trimeresurus mutus, T. monticola, 

 and Ancistrodon rhodostoma. 



Poison.— All are poisonous. Many are fatal to man, but 

 many others rarely, if ever, cause a fatal toxsemia. 



Lepidosis. — The head in some is covered with large shields 

 more or less after the Colubrine type. In others there are 

 only small scales. 



Gostals : Longer than broad ; all rectiform, or some oblique ; 

 smooth or keeled ; with or without apical facets. Vertebrals 

 not enlarged or feebly enlarged. Ventrals ; Broad, three 

 times the breadth of the last costal row ; rounded or laterally 

 keeled. Anal : Entire. Subcaudals : Entire or divided. 



Dentition (for Indian species). — Maxilla : With a pair of 

 canaliculate fangs, and no other teeth. Palatine : Number 1 

 to 6 ; with or without edentulous spaces anteriorly and 

 posteriorly (completely edentulous in Trimeresurus jerdoni). 

 Pterygoid: Number 5 to 19; scaphiodont. Mandibular : 

 Number 10 to 19 ; scaphiodont. 



Distribution. — Europe, Asia, Africa, and America. 



There are thirteen genera arranged in two sub-families. 

 Five are represented in Indian limits, and of these four occur 

 in Ceylon. 



KEY TO THE SPECIES OF VIPERIDJE. 



(For Ceylon Species.) 



(A) Costals in 17 rows at midbody. A 



loreal pit. (See Figs. 96 and 97) . . Ancistrodon. 



(a) Slight boss on top of snout . . A. millardi. 



(b) A horn-like erect appendage on 



snout . . . . A. hypnale. 



(B) Costals in 19 rows at midbody. A 



loreal pit. (See Fig. 98) . . Trimeresurus tri- 



gonocephalus. 



(C) Costals in 29 to 31 rows at midbody. 



No loreal pit. (See Figs. 91 



and 93.) 

 (a) Subcaudals divided . . Vipera russelli. 



(6) Subcaudals entire ' .. Echis carinatus . 



