ANCISTRODON. 423 



Dr. Anderson was the first to notice that this viper makes a 

 curious, prolonged, almost hissing sound by rubbing the folds of 

 the sides of its body against one another. This sound is produced 

 by friction between the serrated keels of the lateral scales, which, as 

 noticed and figured above, are disposed obliquely with their tips 

 directed downwards and backwards ; the noise can even be pro- 

 duced after the death of the animal by twisting the body and 

 thus rubbing or rasping these little saws against one another. A 

 similar arrangement of the scales is found in the African genera 

 Dasypeltis and Cerastes. 



Subfamily II. CROTALIN^E. 



Genus ANCISTRODON, 

 Talisot de Beauvois, Tr. Am. Philos. Soc. iv. 1799, p. 381. 



Head with large symmetrical shields above. Tail ending in a 

 point ; subcaudal shields in two rows in the Asiatic species *. 



North and Central America and Asia. 9 or 10 species are known. 

 Terrestrial. 



Fig. 125. Head of Ancistrodon himalayanus. 



Two species in India : 



Two pairs of large shields on the snout .... A. himalayanus, p. 424. 

 Upper surface of snout covered with small 



shields A. Jiypnale, p. 424. 



* A few of the shields may be single. 



