A MONOGRAPH OF THE BATS OF NORTH AMERICA. 133 



tberefrom by tlie head-fold. The keel (iuterual basal ridge) promi- 

 iieut, well defined. External basal lobe well developed, nearly naked, 

 with base placed well below the line of the month and its anterior 

 border nearly at right angles therewith. Tlie external basal ridge 

 continues with the external border of the auricle and constitutes the 

 margin of the first scallop, which is thus obscurely defined. The 

 second scallop is well-outlined, convex, and ends on the outer surface 

 of the external basal lobe. The tragus is nearly one-half the lieight of 

 the auricle; the broadest part extends from the inconspicuous notch to 

 the apical tliird, where it abruptly narrows to a blunt tip; the anterior 

 border is straight or slightly concave, the posterior convex ("dolabri- 

 form " Leconte). The mentum is well defined and, as a rule, undivided. 

 The pollical callosity is round, conspicuous, 2'"'" wide. No post cal- 

 caral lobe or lobe at tip of the calcar (apici calcaral lobe) is present. 

 A wart is placed well below the angle of the mouth. 



Dorsum throughout of a light ash-grey color, the basal, one-third to 

 two-thirds, being dark-brown. Venter the same, with the brown hues 

 of the shafts being more consi^icuous. The sides of the neck less ash 

 than elsewhere, hence the effect of this region is that of nearly brown 

 throughout. The degree of asliy hue of the dorsum is variable in speci- 

 mens from one locality and may be absent when the hair is uniformly 

 brown, the shaft simj^ly being darker in shade than the tip. The ven- 

 ter is quite constant in color in all individuals examined. 



The material available for study is not sufficient for me to decide 

 which of the two styles of coloration of the dorsum is the most frequent. 

 It may be that the grey variety is a sign of advanced maturity, all the 

 examples were those of lactating females, although some of the brown 

 variety were also in the same condition. 



On the dorsum the hair extended to the middle of the humerus and 

 downward thence to the knee. The interfemoral was turned only at 

 the basal fourth. In the venter the hair extends on the humerus only 

 as far as the end of the pectoral ridge and on the thigh to the proximal 

 and thence along the side of the body to the middle of the thigh. The 

 lower fourth of the interfemoral was alone furred. 



Variafions. — In No. G060 Arkansas (M. C. Z.) the post-calcareal lobe 

 is present. The tragus is less than one-half the height of the auricle. 

 The last caudal vertebra is free. 



In No. 8172 U. S. N. M. (Carlisle, Pa.) is similar to the Southern 

 form, except that the external basal lobe is as high as it is long, and 

 the summit is surrounded, and the inner border of the tragus straight. 

 A large pendant skin-lbld extends tlie entire length of the right side 

 of space below the lower jaw. Tiiis asymmetrical fold is of interest 

 since no similar disposition exists so far as I knoAV in any otlier bat. 



In No. 4735 U. S. N. M. the fur on the dorsum is everywhere dark, 

 lustrous brown at the apical third, and black at the basal; two-thirds 

 on the rump it is brown throughout. On the venter the apical tints 

 are lighter. 



