279 



7. Fam. VIPERIDAE. 



Body round or compressed, covered with imbricate scales 

 with or without apical pits, smooth or keeled; ventrals trans- 

 versely enlarged. Bones of head movable; ectopterygoid present, 

 extending to the mandible; supratemporal suspending quadrate; 

 praefrontal not in contact with the nasal. Maxillary short, 

 vertical, supporting a pair of large perforated poison-fangs; 

 mandible without coronoid; a mental groove. 



Semi-nocturnal; mostly ovoviviparous. All Viperidae are 

 poisonous; they include burrowing, terrestrial, semiaquatic and 

 arboreal forms. Of the two sub-families: Viperinae (without a 

 pit on the snout) and Crotalinae (with a deep pit on each 

 side of the snout) only the latter occurs in the Indo-Australian 

 region. About the occurrence of Vipera russelli (Shaw) be- 

 longing to the Viperinae, in Sumatra and Java, no certainty 

 exists. In BoULENGER's Catalogue III p. 490 this species is 

 mentioned from those islands, Java with a ? ; in DUMERIL 

 & BlBRON VII 1854, p. 1435, a specimen from Java is menti- 

 oned. Other records could not be found and as it is missing 

 in Borneo and the Malay Peninsula this Viper probably does 

 not belong to the fauna of the above-named islands. Its habitat 

 is: Ceylon, India, Burma and Siam. 



Key to the genera. 



A. Head covered above with large symmetrical shields. I. Agkistrodon p. 279. 



B. Head covered above with scales or small shields ... 2. Lachesis p. 281. 



I. Agkistrodon Palisot de Beauvois. 

 (PALISOT DE BEAUVOIS, Tr. Am. Philos. Soc. IV p. 381, 1799). 



Head distinct from neck; eye with vertical pupil. Nine shields 

 on the head or internasals and praefrontals broken up into 

 scales. Body round, covered with smooth or keeled scales, 

 with apical pits. Tail short or moderate; subcaudals single or 

 in two rows. 



Distribution. Round the Caspian Sea; Asia; N. and C.America. 



A single species. 



i. Agkistrodon rhodostoma (Boie). 



Trlgonocephalus rhodostoma^ Boie, Isis, 1827, p. 561. 



Ancistrodon rhodostoma^ Boulenger, Cat. Sn. Ill 1896, p. 527 (s. syn.). 



