A Key to the Genera of North American Mammals 
E. Facial part of head very long; whiskers crenulated. 
HALICH@RUS, 218 
EE. Facial portion of head short, about equal to the brain-case; 
whiskers not crenulated. 
F. Muzzle broad, forehead convex ........ ERIGNATHUS, 218 
FF. Muzzle narrow, forehead sloping gradually. Poca, 215-217 
II. AERIAL MAMMALS WITH THE FORE LIMBS MODIFIED FOR 
FLIGHT AND COVERED BY AN ELASTIC MEMBRANE WHICH 
EXTENDS DOWN THE SIDES OF THE BODY AND BETWEEN 
THE HIND LEGS (BATS). 
A. a wanting; a curious leaf-like appendage on the nose; teeth, 1 3,c4, 
PRO TINGE Oe cS ore ta ah 2s iN tific, et oetaMehelon uals Sale ‘a cueleiens ARTIBEUS, 194 
AA. Tail present; no appendage on the nose. 
B. Tip of tail projecting beyond the interfemoral membrane; teeth,i 4, 
CMe BD) Son pT Ge cctesateys crsesecetoe is Ssecnee hy sieeee! si ahetis Nyctinomus, 195 
BB. Interfemoral membrane reaching to the tip of the tail. 
C. Interfemoral membrane completely covered with fur; teeth, i4, cH, 
TOM alee eyes aia oe entire lapettausiers masts 5 Mars ane LASIURUS, 203-205 
CC. Interfemoral membrane not completely furred. 
D. Ears very large united by their bases; teeth, i 3, c 4, p 3, m 3. 
CORYNORHINUS, 196 
DD. _ Ears not united by their bases. 
E. Upper incisor teeth one on each side close to the canine, 
F. Size large (length 5.60 ins.) ; teeth, i4,c4, p 4, m 2. 
" DASYPTERUS, 206 
FF. Size small (length 3.70 ins.); teeth the same. 
NYCTICEIUS, 206 
EE. Wpper incisors two on each side. 
F. Color of fur black with white tips; teeth, 12, c+, p 2, m 3. 
LASIONYCTERIS, 202 
FF. Color of fur brown or yellowish brown. 
G. Size large (length 4.60ins.); teeth, i 2, c+, p 4, m3. 
VESPERTILIO, 200 
GG. Size vie {length 3-4¢ ins.). 
H. Teeth, 1 3, ¢ 4, p 3, m at Soa PIPISTRELLUS, 201 
ETE. Teeth, 1$,-C Sp oy ag (ee viaesas ey 2 Myotis, 196 
Wl. MAINLY TERRESTRIAL MAMMALS WITH FOUR WELL- 
DEVELOPED LEGS, ADAPTED FOR WALKING.* 
A. Body covered by a bony carapace or shell; teeth, #—§....... TaTu 
AA. Body covered with hair or fur. 
B. Tail naked and prehensile; ears naked; female with teats opening in 
a pouch on the belly in which the young are carried; teeth, 
Me Dy fen SMa chat e eM aie arava, hs Menten vig ene 4 oak ae DIDELPHIs, 4-8 
BB. Tail not prehensile; ears not naked; no marsupial pouch. 
C. Toes terminating in neo. 
D. Form pig-like: CECtH) Af oO ee Pe se Wh Skits wes .TAYASSU, 30 
DD. Form not pig-like; ee (and females of same species) with 
horns. 
E. Horns hollow, ne branched, fitting over a solid bony core; 
teeth, 1 $, c $, p 3, m 3. 
F. Shaggy mane over the head and shoulders ..... Bison, 66 
FF. Longhair over the whole body; horns massive, OVIBOS, 65 
FFF. Form sheep-like; hair short; horns spiral... Ovis, 61-65 
*The hind feet are webbed and somewhat flipper-like in the Sea Otter, and in the Flying 
Squirrels there is an expansion of skin on the sides of the body for flying. 
207 
