10 BULLETIN 18 7, UNITED STATES NATIONAL MUSEUM 



Ck)RRELATION OF GeNEKIC RANGES AND ZOOGECXJEAPHICAL RB14.LMS 



♦Species most numerous in Nearctic. 



t Species slightly more numerous in Neotropical. 



have fiinneled into it from the north is a possibility. Since endemism 

 is represented equally in both Nearctic and Neotropical groups the 

 total picture is not notably changed by inclusion of restricted genera. 

 South America, or Central America, must be considered a center of 

 dispersal of major importance at least for reptiles ; in direct competi- 

 tion with the Nearctic center of dispersal in Mexico, it has produced a 

 notably greater effect. That South America could completely replace 

 North America as a major dispersal center in the epochs to come is 



