454 Field Museum of Natural History — Zoology, Vol. XL 



Interfemoral membrane. 



SECTION 2. Upper surface of interfemoral membrane entirely bare, or furred 



slightly at extreme base; total length (nose to tip 

 of tail) 4 or more inches. 

 Part 1. Ears less than .75 inch long. 



Color of body brown (generally slightly yellowish 

 brown), paler below; ears less than .75 inch 

 long; fur of back, when rubbed, showing de- 

 cidedly darker brown at base; tip of tail ex- 

 tending slightly beyond the interfemoral mem- 

 brane; number of teeth in upper jaw 14; whole 

 number of teeth 32. Brown Bat. 



Eptesiciis fuscus, p. 467. 

 Color of body brown, paler below; ears less than .75 inch long; fur of 

 back, when rubbed, not showing decided darker Ijrown at base; 

 • number of teeth in upper jaw 18; whole number of teeth 38. 



Gray Bat. Myotis grisescens, p. 459. 

 Part 2. Ears more than .75 inch long. 



Ears very large, about one inch or more in length. The extraordinary 

 size of the ears will distinguish this species. Not as yet recorded from 

 within our limits, but may occur in southeastern Illinois. 



Big-eared Bat. Corynorhinus macrotis, p. 476. 

 SECTION 3. Upper surface of interfemoral membrane entirely bare, or furred 

 slightly at extreme base; total length (nose to tip of tail) less than 4 

 inches. 

 Part 1. Upper incisors (front teeth between canines) 2. 



Tail extending slightly beyond the interfemoral membrane; color dull 

 umber brown above, paler below; fur decidedly darker at base; whole 

 number of teeth 30. Rafinesque Bat. 



Nycticeius humeralis, p. 475. 

 Part 2. Upper incisors (front teeth between canines) 4; total length 3.75 

 inches or more. 

 Color of body brown, paler below; length of forearm 1.60 inches (40 mm.) 

 or more. Gray Bat. Myotis grisescens, p. 459. 



Part 3. Upper incisors (front teeth between canines) 4; total length less 

 than 3.75 inches. 

 Color brown, the fur much darker at base; ear when laid forward extend- 

 ing well beyond end of nose; tragus slender. vSay's Bat. 



Myotis subulatus, p. 460. 

 Color brown, the fur much darker at base; ear when laid forward not 

 extending beyond end of nose; tragus rather short and broad. 



Little Brown Bat. Myotis lucifugtis, p. 455. 



