THE QUADRUPEDS OF ARIZONA. 397 
Another genus of Pouched Mice (Perognathus) occurs 
in Arizona. Its species much resemble those of Dipo- 
domys in general appearance. Prominent amongst them 
is the P. penicillatus, also discovered by Dr. Woodhouse 
on the San Francisco Mountains. It is the largest species 
of its genus in the United States. Two others known to 
occur are P. flavus and P. parvus, both of which are 
among the most diminutive of all our animals. Little is 
known of these comparatively rare animals, though it is 
presumed that their habits are in general similar to those 
of Dipodomys. 
Family Muride, the Rats and Mice. A species of this 
extensive family—the Jaculus Hudsonius—is also called 
the “Kangaroo” or “Jumping” Mouse, but must not be 
confounded with the preceding. It belongs to the same 
subfamily (Dipodine) as the Jerboa (Dipus sagitta). It 
has no cheek pouches, and is otherwise conspicuously dif- 
ferent from any member of the Saccomyine. It is of very 
extensive diffusion throughout North America, though I 
believe its actual occurrence in Arizona requires confir- 
mation. 
Exclusive of the Dipodine, the Muride are represented 
in North America by two subfamilies: the Murine, or 
true rats and mice, and the Arvicoline.. The latter is 
composed of the Meadow-mice (Arvicola), the Musk-rats 
(fiber), and the Lemmings (Myodes). The first sub- 
family is usually divided into the Mures, or “Old World 
Rats,” as they are called, and really were originally, 
though they are now cosmopolite ; and the Sigmodontes, or 
“New World Rats,” embracing such forms as the Cotton 
_ Rats (Sigmodon), the Bush Rats (Neotoma), and the 
Field-mice (Hesperomys). I am not aware that any 
“Mures” have as yet made their way into the central and 
