418 VIPEEID^. 



All the snakes of this family are poisonous, and some kinds are 

 amongst the most deadly kuown. Of the Indian forms, Vipera 

 russellii is, after the Cobra, the most dangerous poisonous snake ; 

 next comes the little Eclds carinata, which is also highly poisonous, 

 though less dangerous to man on account of its small size. The 

 Indian Trimeresuri have comparatively much smaller poison- 

 glands, and it has been repeatedly ascertained that their bite does 

 not produce death in man and large animals. The Viperidce are 

 semi-nocturnal, all having the pupil vertically elliptical, and, as far 

 as ascertained, their young are brought forth alive. 



The Viperidw are divided into two very distinct subfamilies : the 

 Vipers proper, Viperince, and the Pit-Vipers, Crotalince, the latter 

 being distinguished by the presence of a deep pit on each side of 

 the snout, between the eye and the nostril. The physiological 

 significance of this pit is still unknown. The Viperince are 

 confined to the Old World, and most abundant in Africa. The 

 Crotalince, of which the Rattle-Snakes are the type genus, are 

 American (ranging from the United States to Patagonia) and 

 Asiatic. 



Synopsis of the Subfamilies and Indian and Burmese Genera. 



A. No loreal pit : Viperina. 



a. Head with large symmetrical shields .... AZEMIOPS, p. 418. 



b. Upper surface of head covered with scales 



or small shields. 

 a'. Lateral series of scales running in 



straight longitudinal lines VIPEHA, p. 419. 



b'. Lateral scales disposed obliquely ; sub- 



caudals in a single row ECHIS, p. 421. 



B. A deep pit between the nostril and the eye : Crotalina>. 



a. Head with large symmetrical shields ANCISTRODON, p. 423. 



b. Upper surface of head covered with scales TRIMERESUHUS, p. 425. 



Subfamily I. VIPERIN^E. 



G-enus AZEMIOPS, 

 Boulenger, Ann. Mus. Geneva, (2) vi, 1888, p. 602. 



Head with large symmetrical shields ; loreal shield present. 

 Scales smooth, in 17 rows. Subcaudals in two rows. 



Only one species, which strikingly resembles a harmless Coln- 

 broid in external appearance. 



519. Azemiops feae. 

 lenff. Ann. Mus. Geno 



Head elliptical, snout short and broad ; rostral broader than 



Azemiops fese, Bouleng. Ann. Mus. Genova, (2) vi. 1888, p. 603, 

 pi. vii. 



