254 University of California Publications in Zoology (Vou. 17 
color in irregular patches, due to the parting of the hairs. Fur upon 
bases of ears grizzled gray throughout. Upon the lower surface of 
the body the bases of the hairs are white, the distal third drab, tipped 
with white, this giving a frosted appearance. The membranes in the 
dried skin are clove brown. In specimens preserved in alcohol the 
colors are essentially the same, save that the ventral surface lacks the 
frosted appearance characteristic of dried skins, and the white bases 
of the hairs are yellowed by the absorption of fat from the body. 
Skull.—Rostrum at orbits twice as wide as at canines (pl. 23, fig. 
54). Auditory bulla conspicuously enlarged, covering almost entire 
cochlea (pl. 24, fig. 62), its greatest diameter distinctly greater than 
width of space between the two bullae. 
22, @il=il 2=2 38) : 
59 jay’ PM ag M39 =34. Upper 
incisors conspicuously unequal in size, and completely bridging space 
between canines; inner pair large, in contact distally, but with roots 
widely separated; lateral pair small, not extending beyond cingula of 
inner pair. Lower incisors small and simple, forming a continuous 
row between canines. Canines strong and simple, with well-developed 
cingula. Area of anterior upper premolar when viewed from side 
almost equaling that of posterior tooth. Second upper premolar with 
main cusp straight, situated at or near middle of crown. First lower 
premolar higher and broader, when viewed in profile, than second 
and third, the third the smallest of the three. Second upper molar 
largest, third upper molar with less than half crown area of second. 
First lower molar smaller than second. 
Measurements—Average and extreme measurements in milli- 
meters of a series of eighteen females from the Colorado Desert are 
as follows: total length, 97.3 (93.0-103.0) ; tail vertebrae, 37.0 (33.0— 
41.0) ; tibia, 23.0 (20.8-24.2) ; foot, 15.6 (14.0-17.0) ; forearm, 49.9 
(46.8-52.6) ; greatest length of skull 23.1 (22.5-23.7); zygomatic 
breadth, 11.2 (10.8-11.6); mastoid breadth, 9.8 (9.2-10.0); inter- 
orbital constriction, 3.5 (3.4-3.7); height of cranium at bullae, 9.4 
(9.8-9.7). The only male at hand measures: total length, 95.0 milli- 
meters; tail vertebrate, 35.0; tibia, 23.0; foot, 14.0; forearm, 48.4; 
ereatest length of cranium, 23.0; zygomatic breadth, 11.1; mastoid 
breadth, 10.0; interorbital constriction, 3.5; height of cranium at 
bullae, 9.3. 
Synonymy and History—This bat was described by Baird (1858, 
p. 116) from a specimen taken at Fort Yuma (Imperial County, Cali- 
fornia, opposite Yuma, Arizona), under the name Macrotus Califor- 
Nicus. 
Coues and Yarrow (1875, pp. 80-81), presuming the lighter color- 
ation of M. californicus to be due to fading in alcohol, and overlooking 
other differences, recorded the species occurring in California as 
identical with M. waterhousii of the West Indies. Dobson (1878, p. 
465) states that his own conclusion that waterhousii and californicus 
are identical was based on descriptions alone, he not having seen the 
type of californicus. 
Teeth—Dental formula: j 
