Bats 
285 
dorsal or upper surface of the metacarpal bone; membranes 
thick and leathery; fibula complete, bowed outwards from the 
tibia and forming an important part of the mechanism of the 
leg; interfemoral membrane short, the tail projecting con- 
spicuously beyond its free edge. 
Genus NYCTINOMUS 
Nyctinomus Geoffroy, Descr. de VEgypte, ii., p. 114 (1813). Type, 
Nyctinomus csgypticus Geoffroy. 
Skull with rounded or somewhat flattened moderately wide 
brain-case, about one and one third times as long as rostrum, above 
level of which it is very slightly elevated, and at least half as deep 
as wide. Sagittal crest scarcely indicated. Ears large and rounded, 
arising from same point on forehead. Laid forward they extend 
distinctly beyond extremity of muzzle ; anterior border of ear conch 
with six to eight horny excrescences; keel well developed; tragus 
small, flattened, squarely truncate above. Muzzle pad well de- 
veloped, sharply outlined, its upper margin thickly set with horny 
points like those on anterior margin of ear ; a line of similar points 
extends downwards across middle of pad between nostrils. Upper 
lip full and wrinkled, rather thickly sprinkled, as are also the muz- 
zle and chin, with stiffened spoon-hairs, the extremities of which are 
slightly expanded. Posterior third or more of tail extending be- 
yond interfemoral membrane. This latter character distinguishes 
this genus from all other genera of bats found in Colorado. 
About forty species of Nyctinomus are now recog- 
nized, which are found in the warmer portions of both 
hemispheres, north to southern Europe and the southern 
United States, east of the Philippines and Norfolk Island; 
eleven species occur in North and Middle America and the 
West Indies, and two have been taken in Colorado. 
Key op the Species 
A. Smaller, forearm, 1.75 ; color dull sooty brown; ears moderate in 
size. N. mexicanus, p. 285 
B. Larger, forearm, 2.4; color dark umber brown; ears large and 
rounded. N. depressus, p. 286 
Nyctinomus mexicanus. Mexican Free- tailed Bat 
Nyctinomus mexicanus Sauss., Rev. Mag. Zodl., 2 me Ser., xii., 
p. 283 (i860). 
