SNAKES OF THE EASTERN STATES 127 



Eocene deposits of France and England, we have no reason 

 to doubt that the family has originated in America. The 

 Cretaceous genera Iguanavus and Chamops from Wyoming, 

 have always been considered as belonging to the Iguanidae. 

 Since the family scarcely enters eastern America, even at the 

 present day, the western States must always have been its 

 headquarters. How the dispersal from the American con- 

 tinent to the Fiji Islands was effected is another problem 

 which I defer to a later discussion. 



As for the genus Sceloporus, to which the swift (S,. undu- 

 latus) belongs, almost all the species inhabit Mexico, that 

 country forming the centre of distribution. From there the 

 genus ranges as far south as Nicaragua;. One species occurs 

 in the western States, while the single northern species, 

 Sceloporus undulatus, ranges from Guatemala to the eastern 

 States. Both the nearest relations of this genus, Phrynosoma 

 and Uta, have their headquarters in the south-western States 

 and Mexico. We possess, consequently, satisfactory evidence, 

 both from its recent as well as its fossil distribution, that 

 the family Iguanidae is of North American origin, and that 

 the latter can be traced to the end of the Mesozoic Era. 



In spite of the occurrence of these three species of lizards 

 in some of the north-eastern States, these reptiles certainly 

 are scarce in the east. It is not so with the snakes. No less 

 than twenty-three different kinds have been observed in the 

 vicinity of New York,* whereas in the whole of France there 

 are only about half that number. The eastern States of 

 America are, in fact, remarkably rich in snakes. Snakes have 

 even penetrated to the eastern islands, for several species, in- 

 cluding the dreaded rattlesnake, occur in Long Island. 



The commonest of these eastern and probably of all the 

 American snakes, is the garter-snake (Thamnophis or Eutenia 

 sirtalis). It is abundant from southern Canada to Florida, 

 and I have met with it even on the edge of the White Moun- 

 tains plateau at a height of 5,000 feet. Very closely allied 

 to, arid scarcely distinct from the genus Tropidonotus, the 

 garter -snakes (Thamnophis) form a most troublesome group 



* Eckel, E. C., and F. C. Paulmier, "New York Keptiles," p. 356 



388. 



