Free edge of interfemoral membrane hairless or only very sparsely 

 sprinkled with hairs 20. 



20. Fur extending on under side of wing membrane to a line joining elbow 



and knee; in the western states 

 Myotis volans (Allen) 

 Fur not extending so far on under side of wings 21. 



21. Ears so long as to reach one-quarter to one-half an inch beyond the nose, 



when laid forward; from Colorado and the Dakotas westward to the 

 coast 



Myotis evotjs (Allen) 

 Ears reaching to, or only slightly beyond, the nose; generally distributed 



22. 



22. Hair of back with glossy tips, giving rather a silky or burnished appear- 



ance, when seen at the right angle 23. 



Hair of back without glossy tips, but with rather a dull, woolly appear- 

 ance 25. 



23. Foot not half as long as tibia; third and fourth fingers usually about 



equal; calcar with a distinct keel; generally distributed 

 Myotis suhulatus (Say) 



(Not the M. suhulatus of most writers, which is M. \eenii 



septentrionahs (Trouessart) ) 



Foot half, or more than half, the length of the tibia; fourth finger usually 



definitely shorter than the third; calcar sometimes thickened, but never 



with a distinct keel 24. 



24. Longer hairs of back about one-third of an inch long; most of temperate 



United States; the most common bat in eastern United States; fairly 

 common in the wooded areas of the western states 



Myotis lucifugus (Le Conte) Little Brown Bat 

 Longer hairs of back only about one-fifth of an inch long; in New Mexico, 

 Arizona and California 



Myotis occultus HoUister 



25. Ears, when laid forward, extending somewhat beyond nostril 26. 

 Ears not extending beyond nostril 27. 



26. Foot small, less than one-half as long as the tibia; calcar with a distinct 



keel; in the western states, from the coast eastward to Utah and Col' 

 orado 



Myotis calif ornicus (Audubon and Bachman) 

 Foot usually one-half as long as the tibia; no definite keel on calcar; east 

 of the Rockies and in northwestern Washington 

 Myotis \eenn (Merriam) 



(Subspecies "septentrionahs (Trouessart)" is the form called 

 M. suhulatus (Say) by many writers) 



27. Hairs of back tricolor — basal two-thirds dark, then a narrow gray band, 



and a brown tip; calcar keeled; foot about one-half the length of the 

 tibia; fourth finger three-fourths as long as the third; in the Mississippi 

 Valley and eastward 



Myotis sodahs Miller and Allen 



486 



