AMERICAN" BATS OF THE GENERA MYOTIS AND PIZON"YX 83 



Ala. (U.S.N.M.), both phases are represented by adults: The dusky 

 as above described ; and the russet, a nearly uniform " cinnamon- 

 brown " above to the roots of the hairs, the lower surfaces with the 

 whitish tips replaced by a pale buff, contrasting with the darker 

 bases of the hairs. 



Skull. — The skull differs from that of Myotis lucifugus in its larger 

 size. In shape and proportions the crania of the two species are prac- 

 tically alike, but the evident sagittal and lambdoid crests make the 

 skull of Myotis grisescens readily distinguishable. 



Teeth. — The two small upper premolars stand nearly in the tooth 

 row so that both are clearly visible in side view, while from below, 

 a line connecting the posterior angle of the canine and the anterior 

 corner of the large p* passes through the outer part of both the other 

 premolars. In tii^ and m^ the protoconule is unusually well de- 

 veloped, but in actual structure the small cusps and their accompany- 

 ing ridges do not differ from those which occur in Myotis lucifugits. 

 Cingulum on inner side of crown in m^ and rnr well developed and 

 conspicuous, but apparently never extending around the antero- 

 lingual base of the protocone. At the postero-lingual base of the 

 hypocone the cingulum frequently becomes so thickened as to re- 

 semble a low cusplike tubercle applied to the base of the hypocone. 

 This tubercle may in rare instances (No. 202022, U.S.N.M.) become 

 so large that it bears at its summit a distinctly worn area produced in 

 m- hy the protoconid of m.^ and in m^ by the protoconid of mg. Tlie 

 teeth of the lower jaw sliow no special characteristics. 



Measurements. — For measurements see tables, pages 84 and 85. 



Specmiens examiined. — Total number 258, from the following 

 localities : 



ALABAMA: Anniston, Calhoun County, 2 ale. (M. O. Z.) ; Fort Deposit, 



Marshall County, 10 skins, 8 ale. (U.S.N.M.) ; Rogersville, Lauderdale 



County, 12 skins, 49 ale. (U.S.N.M.). 

 ARKANSAS: [? Osase River], 1 ale. (M. C. Z.). 

 ILLINOIS: Rosiclare, Hardin County, 12 skins, 33 ale. (F. M.). 

 MISSOURI: Columbus, 1 ale. (U.S.N.M.): Marble Cave, Stone County, 



12 skins, 3 ale. (U.S.N.M.). 

 TENNESSEE: Indian Cave, Grainger County, 13 skins (Univ. Wisconsin), 



15 ale. (U.S.N.M.), 1 skin (M. C. Z.) ; New Market, Grainger County. 



1 skin (M. C Z.) ; Nicka.1aek Cave, Marion County, 21 skins, 62 ale. 



(U.S.N.M.), 1 ale. (A. N. S. P.) ; Shell Mound, 1 ale. (U.S.N.M.). 



Habits. — An interesting point in connection with the fact that 

 colonies of Myotis grisescens frequent the same caves in both summer 

 and winter is the segregation of the sexes at certain times of year. 

 The breeding females seem to congregate apart from the males. The 

 young are probably born in early July, and when these are well 

 grown a breeding colony naturally contains the adult females as well 

 as immature bats of both sexes. But in August, the colonies seem 



