﻿PIPISTRELLUS HESPERUS. 



89 



membranes attached at base of toes. Uropatagiiim extendiug ahiiost 

 to extreme tip of tail. 



Feet. — Foot small, distinctly less than half as long as tibia, naked or 

 with a few almost invisible whitish hairs on dorsal snrface. Calcar 

 about as long as tibia, scarely keeled on posterior edge, terminal lobe 

 absent or very indistinct. 



Fu7' and color, — The fur extends on basal third of ears, but barely 

 reaches extreme base of interfemoral membrane, and on wing mem- 

 branes invades merely a very narrow strip close to body. 



Color light yellowish gray or whitish gray, the fur everywhere deep 

 plumbeous at base. In some specimens the hairs on the back have faint 

 dark sub terminal areas which, however, are visible on close insiiection 

 only. Ears, muzzle, face, and membranes black. A narrow whitish 

 border on wing membrane between foot and fifth finger. 



This species is apparently much more constant in color than P. suh- 

 Jlavus, but the absence of a good series of skins leaves the range of 

 individual variation in color a matter of uncer- 



tainty. 



Slxull. — The skull of PipistreJIus hesperus 

 (figs. 21 a, and 22 h) is very small, thin, and 

 papery. That of an adult male from Fort 

 Bowie, Arizona, measures 11.4 mm. in occipito- 

 nasal length, G mm. in zygomatic breadth, and 



4 mm. in occipital depth. The dorsal outline fi^. 2i.-Top view of sM of 

 is nearly straight from external nares to occi- («) Pip'streUus hesjx-rus ami 

 put, though there is a slight concavity between <2.) 

 the orbits and a slight convexity over the brain case. Muzzle broad 

 and nearly flat, slightly concave on each side of median line. In gen- 

 eral the skull of Fipistrelhis hesperus suggests a miniature of that of 

 Lasionycteris. 



Teeth. — The teeth of PipistrelJus hesperus (fig. 23 a) do not differ 

 materially from those of P. suhflarus. The anterior upper premolar is 

 minute (much smaller than the smaller upper incisor) and usually 

 thrown out of the tooth row by the second premolar, the anterior edge 

 of which is generally in contact with the canine. 



Measurements. — See table, page 95. 



Specimens examined. — Total number 127, from the following localities : 



Arizoua: Beaverdam, 1; Fort Bowiej 1 (skin); Graud Canon, 2; Guadalupe 

 Canon, Cochise County, 4 (skins) ; Little Colorado, 2; Dos Cabezas, 1 Cskin) ; 

 Keam Canon, Navajo County, 1 (skin); New River, Maricopa County, 1; 

 Yuma, 2. 



California: Borax Flat, Moliave Desert, 3; Colorado Desert, 1 (skin); Death 

 Valley, 4; Funeral Mountains, Inyo County, 1 ; Furnace Creek, Death Valley, 

 1; Grapevine Spring, Death Valley, 1; Independence, 1; Hot Springs Valley, 

 Inyo County, 2; Jacumba, San Diego County, 2 (skins); Keeler, 1; Kern 

 River, 3; Kernville, 1; Lone Pine, 3; Owens Lake, 1; Palm Springs, 3; Pana- 

 mint Valley, Inyo County, 6; Pananiint Mountains, 4; Poso Creek, Kern 

 County, 1 (skin); Saline Valley. Inyo Connty, 1; San Emigdio, 1; Santa 



