278 The Mammals of Colorado 
to a narrowly rounding tip; tragus straight or slightly curved 
forward. Back of interfemoral membrane sprinkled with hair on 
basalthird. Mammae2. Dentition, i. f; c. pm. f; m. f X 2 = 34. 
The members of this genus are all small, some of them the 
smallest of known bats. About forty species are now 
recognized in the genus; these are found on the entire main- 
land of the Eastern Hemisphere to the limits of tree growth, 
and also in the Malay Archipelago, New Guinea, Solomon 
Islands, and northern Australia; in America from the northern 
United States (except in the Boreal Zone) to southern Mexico. 
Of these forty species four species and three subspecies are 
found in North and Middle America, and one, P. hesperuSf 
has been taken in Colorado. 
Pipistrellus hesperus (Lat. the evening star). Western Bat 
Scotophilus hesperus H. Allen, Monogr: N. Am. Bats, p. 43 (1864). 
Type locality. — Fort Yuma, California. 
Measurements. — Total length, 3.0; tail vert., 1.2; hind foot, 0.2; 
forearm, 1.20. Length of skull, 0.42; width, 0.3. 
Description. — (From a specimen taken at Fort Bowie, Arizona, 
May 2ist): Color above and below light yellowish gray, hairs 
plumbeous at base ; ears, muzzle, face, and membranes black. 
Cranial and dental characters as for genus. The anterior upper 
premolar is very minute and usually thrown out of tooth row by the 
second premolar. The very small size distinguishes it from all other 
Colorado bats. 
Distribution. — Lower Austral Zone in the western United States 
from western Texas to the Pacific Coast. Limits not known 
(Miller I. c). He records it from Grand Junction and I have taken 
it at Bedrock, on the Dolores River in Montrose County, 5,150 feet. 
Genus EPTESICUS 
Eptesicus Rafinesque, Annals of Nature, p. 2 (1820). Type, 
Vespertilio fusciis Beauvois. 
Revision, Miller, N. A. Fauna, No. 13 (1897). 
Skull large and heavily built, rostrum broad in proportion to 
brain-case, scarcely concave at sides back of nasal aperture ; dorsal 
profile nearly straight, rising gradually from external nares to 
occiput, which in the adult is strongly angular and provided with a 
conspicuous sagittal crest. Ears short, considerably narrower than 
