Bats 
281 
Revision, Miller, A^. A. Fauna, No. 13 (1897). (There called 
Lasiurus.) 
Skull broad, short, and deep, very different in form from that of 
any of the other genera of bats found in Colorado ; brain-case high 
and rounded, the rostrum sloping away rapidly in front so that 
its upper surface is nearly in line with that of brain-case. Palate 
sloping upward anteriorly, and floor of brain-case rising posteriorly 
so that the two surfaces are set at noticeably different angles. Ear 
short, rounded. Interfemoral membrane very large, most of its 
upper surface furred. Mammae four, the only genus having this 
number. 
Dentition, i. | ; c. {; pm. |; m. f X 2 = 32; anterior upper pre- 
molar at base of canine on inner side. 
The members of this genus are recognizable among North 
American Bats by their thickly furred interfemoral mem- 
branes. 
About a dozen forms are now recognized, distributed in 
America to the limits of tree growth, including the Bahama 
Islands and Greater Antilles; also the Galapagos and 
Hawaiian Islands. Of these two species have been met 
with in Colorado. 
Key of the Species 
A. Size large, forearm more than 2.0; color brown, hairs tipped 
with silvery white. N. cinereus, p. 282 
B. Smaller, forearm, 1.5; color reddish. N. borealis, p. 281 
Nycteris borealis (Lat. Boreas, the god of the North 
Wind). Red Bat. 
Vespertilio borealis MuUer, Natur. Syst., Suppl., p. 21 (1776). 
Lasiurus borealis Warren, Mamm. of Colo., p. 268 (1906). 
Type locality. — New York. 
Measurements. — Total length, 4.3; tail vert., 2.0; hind foot, 0.8; 
forearm, 1.60. Length of skull, 0.5; width, 0.35. 
Description. — (Compiled from Miller): Fur everywhere full and 
soft, covering whole dorsal surface of interfemoral membrane ; the 
color varies much, ranging from bright rufous red or fawn color 
to yellowish gray; red specimens are rufous red throughout, paler 
and more fawn colored on belly ; the hairs of the back usually with 
distinct grayish tips, these on throat and chest tipped with whitish. 
