234 



GEOGRAPHICAL ZOOLOGY. 



[PART iv. 



FAMILY 60. CASTOKID^E. (1 Genus, 2 Species.) 



GENERAL DISTRIBUTION. 



The Beavers, forming the genus Castor, consist of two species, 

 the American (Castor canadensis) ranging over the whole of 

 North America from Labrador to North Mexico ; while the 

 European (Castor fiber) appears to be confined to the temperate 

 regions of Europe and Asia, from France to the Eiver Amoor, 

 over which extensive region it doubtless roamed in prehistoric 

 times, although now becoming rare in many districts. 



Extinct Castoridce. Extinct species of Castor range back 

 from the Post-pliocene to the Upper Miocene in Europe, and to 

 the Newer Pliocene in North America. Extinct genera in Europe 

 are, Trogoniherium, Post-Pliocene and Pliocene ; Chalicomys, 

 Older Pliocene; and Steneofiber, Upper Miocene. In North 

 America Castoroides is Post-Pliocene, and Palceocastor, Upper 

 Miocene. The family thus first appears on the same geological 

 horizon in both Europe and North America. 



FAMILY 61. SCIUKIDJE. (8 Genera, 180-200 Species.) 

 GENERAL DISTRIBUTION. 



The Squirrel family) comprehending also the marmots and 

 prairie-dogs, are very widely spread over the earth. They are 

 especially abundant in the Nearctic, Palaearctic, and Oriental 

 regions, and rather less frequent in the Ethiopian and Neotro- 

 pical, in which last region they do not extend south of Paraguay. 

 They are absent from the West Indian islands, Madagascar, and 

 Australia, only occurring in Celebes which doubtfully belongs 

 to the Australian region. The genera are as follows ;- 



