Frp., 1912. MAMMALS OF ILLINOIS AND WISCONSIN — Cory. 451 
Family VESPERTILIONIDA. Typical 
Bats. 
This is by far the largest family belonging to the order. Its mem- 
bers are insectivorous, nocturnal and crepuscular; and are characterized, 
by having the ears separate, with a small anterior basal lobe and 
tragi well developed. The muzzle is simple, without fleshy appendages 
(differing in this from the so-called Leaf-nosed Bats); tail attached 
to interfemoral membrane and extending to its edge or slightly beyond; 
clavicle present and well developed; radius long and curved; ulna 
rudimentary; pollex free from and extending beyond edge of wing 
membrane, ending with a hooked claw; presternum with prominent 
“keel”? for the attachment of the large pectoral muscles; ribs much 
flattened and occasionally more or less anchylosed at their margins; 
cerebral hemispheres smooth; placenta discoidal and deciduate; mam- 
me thoracic; testes abdominal or inguinal. The milk teeth are unlike 
the permanent teeth and are usually replaced by the latter at an un- 
usually early period, the cranial sutures become anchylosed and often 
disappear much earlier in life than in most of our mammals. The 
structural character of the hair is peculiar.* 
Of the 100 or more North American species and subspecies, nine 
species belonging to 6 genera are known to occur within our limits, and 
it is probable that another genus and species (Corynorhinus macrotis) 
and possibly a representative of another family (NV yctinomus depressus) 
may ultimately be added to the list. 
KEY TO THE GENERA. 
GROUP 1. Upper incisors (front teeth between canines) 2. 
Upper surface of interfemoral membrane (membrane 
connecting tail with legs) completely furred; whole 
number of teeth 32. Genus NYCTERIS, p. 470. 
Upper surface of interfemoral membrane entirely bare 
or furred slightly at extreme base; whole number 
of teeth 30. Genus NYCTICEIUS, p. 475. 
hmnaseee 
__ Front view, showing up- 
per incisors and canines 
much enlarged. 
* For remarks concerning the structural variation in the hair of Bats, see page 446. 
