FEB., 1912. MAMMALS OF ILLINOIS AND WISCONSIN CORY. 451 



Family VESPERTILIONID^. 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- 

 mae 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 (Nyctinomus 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 

 Front view, showing up- of teeth 30. Genus NYCTICEIUS, p. 475. 



per incisors and canines 

 much enlarged. 



* For remarks concerning the structural variation in the hair of Bats, see page446. 



