212 



TIPERID^. 



presence (Crctalince) or absence (Viperince) of a deep pit on each 

 side of the suout, between the nostril and the eye. The Vipennce 



jom. 



ar. Articular. 

 bo. Basioccipital. 

 ca. Columella auris. 



d. Dentary. 

 eo. Exoccipital. 



/. Fruntal. 



Fig. 63. — Skull of Lachesis gramineus. 

 A. Upper view. E. Side view. 



m. Maxillary. 



«. Nasal. 



J}. Parietal. 

 pf. Poison- fang. 

 pm. Pn^maxillary. 

 prf. Prae frontal. 



2y>'o. Prootic. 



pt. Pterygoid. 



ptf. Postfrontal. 



r/. Quadrate. 



$/. Supratemporal. 



tp. Transpalatiue. 



are not represented in the Malay Peninsula, from which only two 

 genera of Crotalince are known : — 



Upper surface of head covered with large 



symmetrical shields Ancistrodon, p. 212. 



Upper surface of head covered with scales or 



small shields Lachesis, p. 214. 



Genus ANCISTRODON. 

 Palisot de Beauv. Tr. Am. Philos. Soc. iv, p. 881 (1799). 



Pupil vertical. Upper surface of head with nine lai-ge sym- 

 metrical shields. Body cylindical ; scales smooth (or keeled), 

 with apical pits. Tail moderate or short; subcaudals in two 

 rows (or single). 



Alia, North and Central America. 



A single species in the Malay Peninsula. 



