426 DISEASES DUE TO VENOMS AND POISONS 



the Indian Ocean. Their fangs are small, but the venom, though but 

 little is injected, is the most potent known. It is chiefly neurotoxic. 



The Genera are : Distera, Acalyptus, Hydrophis, Enhydrina, 

 Hydrelaps, Hydrus, Thalassaphis, Enhydris, Platurus and Aipysurus. 



(II) Yiperidae. 



These have a triangular head, short neck, stout body, stumpy tail, 

 and tubular poison glands situated anteriorly, which are provided with 



Bung-ants fasdatus (India). (After Sir Joseph Fayrer.) 



fangs having a large foramen for the venom. There are 120 species, 

 some of which live in trees, but all are dangerous to man. There are 

 two groups : — 



(i) Crotalin^, with a deep sensory pit between the eye and the 

 nostril on each side. These include rattlesnakes, such as : — 



Crotalus, with many small scales on the top of the head. 



Sisturus, with nine large scales on the top of the head. 



Ancistrodon. 

 (2) ViPERiN^, having no sensory pit as the Crotalinas. Amongst 

 them are : — 



Vipera berus, the English adder. 



Vipera russelli, the handsome Indian viper. 



