AMEEICAN BATS OF THE GENERA MYOTIS AND PIZONYX 5 



Among the Old World members of the genus there are species in 

 which the foot is more enlarged than in any of those known from 

 America (ratio of foot to tibia rising as high as 64 and T6), the wing 

 attachment is at a point a little above the ankle, and the fur is 

 rather dense and woolly in appearance. The subgeneric name Leu- 

 conoe has been applied to these bats; and Thomas formally raised 

 the group to generic rank in 1915.^ The occurrence of various inter- 

 mediate conditions, however, seems to us to make generic recognition 

 undesirable. Though Thomas has referred Myotis Jucifugus cai^- 

 sima to the Leucono'e group, the nearest approach to this type of bat 

 in America is probably Myotis grisescens of the southeastern United 

 States, the American species with the highest ratio of foot to tibia, 

 and one of the two in which the wing membrane comes off from the 

 tarsus instead of from the side of the foot. A large-footed animal 

 resembling Myotis inacrotarsus of the Philippine Islands has been 

 described under the name Vespertilio pilosus from a supposed South 

 American locality. No second specimen of this bat has been taken, 

 and the species must for the present be regarded as doubtfully 

 American. * 



The presence or absence of a keel on the outer edge of the calcar is 

 a character of importance in the identification of species. This struc- 

 ture is a widening of the long spur that helps to spread the margin 

 of the interfemoral membrane. It is convex in outline, beginning to 

 rise at a distance from the heel equal to about the width of the foot. 



Fur and color. — The body is well furred, and the hairy covering 

 usually extends thinly on the under side of the wing to a line joining 

 the knee and the distal half or third of the humerus. In Myotis 

 volans it reaches the elbow. In some species there is a fringe of 

 short hairs on the free edge of the interfemoral membrane; this 

 fringe is slightly developed in M. evotis^ very conspicuously in M. 

 thysmiodes. Usually the fur is soft and silky, but sometimes, as in 

 the South American M. simus and the North American M. austro- 

 riparius, it assumes a decidedly velvety or woolly texture. The tips 

 of the longer hairs may be burnished and glistening (as in Myotis 

 lucifugus) or dull (as in M. calif omicus) . When the hairs of the 

 back are smoothly parted two well-contrasted color zones are ordi- 

 narily exposed, a darker slaty area involving the bases of all the 

 hairs and a lighter distal area formed by the tips of the shorter hairs 

 and determining the general hue of the upper parts. Occasionally the 

 contrast is not very noticeable, and rarely (as in M. grisescens or in 

 forms which have undergone unusual general darkening) it may be 

 essentially absent. Ordinarily the tips of the longer dorsal hairs do 

 not form an obvious third color band ; hence the absence of a tricolor 



»Journ. Bombay Nat. Hist. Soc, vol. 23, p. 607. 



