590 REPTILIA [CH. 



Those which crush their prey are confined to the tropics ; those 

 which swallow their prey directly are the non-venomous snakes, and 

 are represented in both England and North America by the family 

 COLUBRIDAE. In this family the maxilla is long and bears numerous 

 teeth, as do also the pterygoid and the lower jaw. The head is 

 much broader behind than at the muzzle and passed into the trunk 

 without any constriction to mark a neck. There are about thirty 



FIG. 292. The Texas Rattlesnake, Crotalus atrox, reduced. From Stejneger 

 after Baird and Girard. 



species belonging to eighteen genera in North America, of which 

 Tropidonotus (Eutainia) sirtalis, the Garter-snake frequently met 

 with in Canada, is one of the commonest; and in England the 

 family is represented by two species, the Smooth-snake, Coronella 

 laevis, and the Grass- or Ring-snake, Tropidonotus natrix. 



The venomous Snakes in America belong to two families and 

 these two families are not closely allied and have quite different 



