234 
GEOGRAPHICAL ZOOLOGY. 
[PART IV. 
Family 60. — CASTOKIDiE. (1 Genus, 2 Species.) 
General Distribution. 
Neotropical 
Sub-regions. 
N EARCTIC 
Sub-regions. 
Pal.e arctic 
Sub-regions. 
Ethiopian 
Sub-regions. 
Oriental 
Sub- regions. 
Australian 
Sub-regions'. 
— 
1 , 2 . 3 . 4 
1 - 3 - 

— 
— 
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 Kiver Amoor, 
over which extensive region it doubtless roamed in prehistoric 
times, although n6w 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, Trogontherium, Post-Pliocene and Pliocene ; Chalicomys , 
Older Pliocene ; and Steneofiber, Upper Miocene. In North 
America Castor oides 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. — SCIUEIDiE, — (8 Genera, 180-200 Species.) 
General Distribution. 
Neotropical 
Sub-regions. 
Nearctic 
Sub-regions. 
Palsearctic 
Sub-regions. 
Ethiopian 
Sub-regions. 
Oriental 
Sub-regions. 
Australian 
Sub-regions. 
- a. 3 - 
1 .2.3.4 
Jl.2.3.4 l 
! 1.2.3- 
1 .2.3 .4 
— 
The Squirrel family, comprehending also the marmots and 
prairie-dogs, are very widely spread over the earth. They are 
especially abundant in the Nearctic, Palsearctic, 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 : — 
