CHAP. XVII.] 
MAMMALIA. 
233 
Family 59. — SACCOMYIDAS. (6 Genera, 33 Species.) 
General Distribution. 
Neotropical 
Sub-regions. 
Nearctic 
Sub-regions. 
Palaearctic 
Sub-regions. 
Ethiopian 
Sub-regions. 
Oriental 
Sub-regions. 
Australian 
Sub-regions. 
- 
1 . 2 . 3 . 4 
The Saccomyicke, or pouched rats, are almost wholly confined 
to our second Nearctic sub-region, comprising the Eocky Moun- 
tains and the elevated plains of Central North America. A few 
species range from this district as far as Hudson’s Bay on the 
north, to South Carolina on the east, and to California on the 
west, while one genus, doubtfully placed here, goes south as far 
as Honduras and Trinidad. The group must therefore be consi- 
dered to be pre-eminently characteristic of the Nearctic region. 
The genera are, — Dipodomys (5 sp.), North Mexico, California, 
the east slope of the Eocky Mountains to the Columbia Eiver, and 
one species in South Carolina ; PerognatJms (6 sp!), North Mexico, 
California, east slope of the Eocky Mountains to British 
Columbia; Thomomys (2 sp.), Upper Missouri, and Upper 
Columbia Bivers to Hudson’s Bay ; Geomys (5 sp.), North Mexico, 
and east slope of Eocky Mountains to Nebraska (Plate XIX., 
vol. ii. p. 129) ; Saccomys (1 sp.), North America, locality un- 
known ; Heteromys (6 sp.), Mexico, Honduras, and Trinidad. 
Geomys and Thomomys constitute a separate family Geomyidae, 
of Professor Carus ; but I follow Professor Lilljeborg, who has 
made a special study of the Order, in keeping them with this 
family. 
In the Post-Pliocene deposits of Illinois and Nebraska, remains 
of an existing species of Geomys have been found. 
