82 BULLETIIT 144, UNITED STATES NATIONAL MUSEUM 



this species frequents these caverns regularly in summer, as well as 

 during the hibernation period, so that the grisescens population is 

 more concentrated than in the case of those species (as M. lucifugus, 

 M. keenii septentHonalis) that largely desert the caves in sunmier. 

 ]y[owell (1909, 1921) has given a brief account of these Tennessee 

 caves and their bat population. 



Diagnosis. — Size decidedly greater than in Myotis lucifugus^ but 

 general proportions not strikingly different (ratio of tail to head and 

 body in 10 topotypes, 76.4) ; forearm usually more than 40 mm. ; 

 greatest length of skull ranging from 15.5 to 16.5 mm., maxillary tooth 

 row ranging from 5.8 to 6.2 mm., lower tooth row more than 6 mm. 

 (6.2 to 6.6 mm.) ; skull with an obvious sagittal crest in adults; cheek 

 teeth proportioned to the palate as in M. lucifugus., not enlarged as in 

 M. velifer; first and second upper molars with protoconule unusually 

 well developed; a broad, conspicuous cingulum on inner margin 

 of crown. Differs from all other known North American species in 

 the insertion of the wing membrane at the tarsus instead of the side 

 of the foot and in the absence of dark bases to the hairs of the back. 



Ears. — The ears are about as in Myotis velifer: when laid for"\vard 

 reaching the nostril or slightly beyond it. Tragus as in M. velifer^ 

 with bluntly pointed tip. 



Wing and mnemhranes. — ^Wing membranes from the base of the 

 tarsus instead of from the base of the toes as in all known North 

 American species, a character which, though obvious in alcoholic 

 specimens, is often obscure in skins if the membrane is stretched 

 laterally in drying. Metacarpals graduated, the third longest, the 

 fourth and fifth successively shorter. Taking the third finger as 

 100, the fourth is 86, the fifth 80. When the wing is folded the third 

 metacarpal falls 4 mm. short of the elbow. 



Foot. — Except for their larger size the foot and calcar resemble 

 those of Myotis lucifugus^ though the foot is longer proportionally 

 to the tibia. In 10 topotypes the ratio of foot to tibia averages 60.1 ; 

 in 10 specimens from Illinois it averages 58.8. 



Fur and color. — The fur is more velvety than in Myotis lucifugus, 

 and the hairs of the dorsal surface are strikingly characterized by 

 being of essentially the same tint throughout instead of conspicuously 

 darker at the base. There are two color phases: dusky and russet. 

 The former is represented by the series of 20 skins from the type 

 locality, Nickajack Cave. These average darker than the other avail- 

 able speciijiens, and are a uniform smol^ (about "chsetura drab") 

 above to the roots of the hairs ; below paler, the hairs " dark mouse 

 gray " at their bases with dull whitish tips, those of the chin lighter, 

 and those between the thighs whitish throughout. 



Specimens from Indian Cave, Tenn., and from Rosiclare, lU., are 

 of a slightly warmer tint. In a series of 12 skins from Rogersville, 



