230 Zoologica: N. Y. Zoological Society [I; 11 



The writer has had no opportunity to study living examples of 

 the Amblycephalidae. Systematic observations may reveal interest- 

 ing traits among these snakes, characterized by the small gape and 

 limited dilatability of the swallowing mechanism. Apparently con- 

 necting the Colubridae with the Viperidae, their methods of feeding 

 and the kind of food selected are characters which should be noted 

 together with their alleged relationship. 



The Viperine Snakes: Among these, the most highly specialized 

 forms of reptile life we find what appear to be indications of well- 

 defined food selection following the trend of specializa on. Although 

 there is an immediate relationship between New and Old World 

 species of the Crotalinae, the writer believes there should be generic 

 distinction between the New and Old World species of Ancistrodon 

 and Lachesis. He bases this opinion upon preliminary studies of his 

 friend Dr. Joseph E. Tompson, who explains that the hemipenial 

 characters of the species of the Eastern Hemisphere are markedly 

 different from the New World Crotaline snakes under the same 

 generic rating. From the standpoint of relationship and food the 

 New World Crotalinae may be thus defined: 



Sistrurus 



(Cold and warm-blooded prey) 



Ancistrodon. 



(Cold and warm- 

 blooded pray)^ 



(Warm-blooded prey) 



Lachesis mutus ^ \ i 

 6 rotalus 



(Warm-blooded prey) 



Other species of 

 La chesis 



(Cold and warm- 

 blooded prey) 



The species of Ancistrodon, apparently representing an older 

 tjrpe of development, possess relatively short fangs. Unlike the more 



