300 E. G. LINSLEY 



a Neotropical element (largely austral), an Alleghenian element 

 (centering mainly in the Appalachian and Ozark plateaus), a 

 Vancouveran element (centering along the Pacific Coast), and a 

 Sonoran element (centering in southwestern United States and 

 northern Mexico). 



The modern Holarctic and Neotropical constituents are of 

 relatively recent derivation and endemism is expressed largely at 

 the species level (Table I). The Alleghenian, Vancouveran, and 

 Sonoran elements are of more ancient origin, although the first two 

 were apparently derived largely from an early Holarctic fauna, 

 and the last originated almost entirely from the early Neotropical. 

 Much of the endemism in these subfaunas is at the generic level 

 (Tables I and II). 



