340 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



Genera of the North American Region — Continued. 



Genera. 



Sciurus 



Tamias 



Spermophilus . 



Cynomys 



Arctomys 



Haplodon 



jSTeotoma 



Sigmodon 



OCHETODON . . . 



Hesperomys . . 



Arvicola 



Evotomys 



Synaptomys - . 



Fiber 



Zapus 



Perognathus . 

 Ckicetodipus . 

 Dipodomys . . . 



Geomts 



Thomomys 



Castor 



Erethizon 



Lagomys . . 

 Didelphys 



Subregions. 



+ 

 + 

 + 

 — ? 

 + 



+ 



+ 



+ 



+ 

 + 

 — ? 



4- 



+ 



+ 

 + 

 + 

 + 

 + 

 + 

 + 

 + 

 + 

 + 



+ 

 + 

 + 

 + 

 + 

 + 

 + 



+ 



+ 



+ 

 + 

 + 



+ 

 + 

 + 

 + 

 + 

 + 



Summary. 



Whole number of genera 



Peculiar to tlie region , 



Circumpolar 



Of general distribution throughout the region . . . 

 Occurring in the Cold Temperate Subregion. 



72 



'. 23 



32 



26 



47 



Occurring in the Warm Temperate Subregion 53-56 



Land genera represented in the Eastern Province 47 



Genera represented in the Middle Province 51 



Land genera represented in the Western Province 48 



Land genera restricted to the Eastern Province *6 



Genera common to the Middle and Western Provinces not represented in the 



Eastern Province 8 



Genera restricted to the Middle Province , 2 



Land genera restricted to the Western Province t3 



Maritime genera restricted to the Eastern Province 5 



Maritime genera restricted to the Western Province 5 



Maritime genera occurring in both Eastern and Western Provinces 1 



* Plus 5 maritime = 11. 



t Plus 5 maritime =^ 7. 



