138 GLIRES. 
against the attacks of the Coyote and other enemies. If the entrance happens to be in 
an exposed place, it is sometimes fortified with thorny pieces of the mesquite and cacti. 
Though somewhat companionable, each, as a rule, seems to have its own house. Like 
other mammals, it is most above ground in the morning and evening in search of food ; 
yet it is the least affected by the heat of the midday sun. It is omnivorous. Its bed. 
is a globular mass, lined with soft material, and has but one entrance” *. 
4, CYNOMYS. 
Cynomys, Rafinesque, Amer. Monthly Mag. ii. p. 45 (1817, fide Baird, Mamm. N. Am. 
p- 829). 
Anisonyz, Rafinesque, loc. cit. 
The well-known “ Prairie-Dogs” or Prairie-Marmots of North America are very 
closely allied to the Spermophiles, but are of more thickset form, and have well-deve- 
loped claws on all their toes. Their cheek-pouches are shallow; their grinding-teeth are 
placed obliquely, so that they converge strongly behind; and their skulls present slight 
but constant differences. 
Only two species are known, Cynomys ludovicianus and the western C. columbianus. 
The former, which is the only species hitherto recorded from Mexico, may be readily 
distinguished by its size, its reddish-brown colour, and its comparatively long tail, which 
is brownish-black towards the tip, instead of whitish, as in C. columbianus. It averages 
about 12 inches in length of head and body; and the tail-vertebre measure about 
34 inches. 
1. Cynomys ludovicianus. 
Arctomys ludovicianus, Ord, Guthrie’s Geogr., 2nd Amer. ed., pp. 292, 302 (1817, deser. orig., fide 
Baird, Mamm. N. Am. p. 331)’. | 
Cynomys ludovicianus, Baird, Rep. U.S. Mex. Bound. Surv. 1. Mamm. p. 397; Dugés, La Nat. i. 
p. 137°; Allen, Mon. N.-Am. Rodent. p. 892%. 
Perrito, Perrito del campo, of Mexicans? . 
Hab. NortH America, east of the Rocky Mountains, from lat. 49° southwards+.—Mexico, 
Chihuahua (Kennerly”, Dugés*). 
The range of the Missouri Prairie-Marmot extends to the Mexican State of Chihuahua, 
where its occurrence has been recorded by the naturalists of the United-States Boundary 
Survey and by Dr. Dugés®. Dr. Kennerly says that to the west of the Rio Grande it 
was observed as far as the Sierra Madre?. 
Much has been written on the habits of the Prairie-Dog, of its “ towns” or “ villages,” 
and of its strange fellow citizens, the Prairie-Owl (Speotyto cunicularia) and the Rattle- 
Snake (Crotalophorus confluentus), with which it is popularly but erroneously believed 
