4 NORTH AMERICAN BATS — II. ALLEN. 



long' period the endopatagiuiu has functions which are not exacted of 

 the rest of the wing- meiubraue, and in consequence, in my judgment, 

 it is easy to see how this portion of the wingex])anse should be dis- 

 tinguished from those portions which are used only in Hight. 



The digits on their palmar aspect may be sharply detined as in the 

 Phyllostomida* and Corynorhinns, or they may be obscured by the mem- 

 brane or the upper i)art in the forepart of the hand, namely, in the 

 region of the second, third, and fourth digits, as in Molossi, Vesperti- 

 lionidie and the genus Antrozous. The membiane may lie chietiy on 

 the upper aspect of the digits, as in most bats, or at the lower. That 

 in the second interspace may be attached to the upper border of the 

 second and to the lower border of the third metacarpal bone. 



The skin is much more loose about the legs than the arms and on the 

 iuterfemoral membrane than the wing membrane. The membranes are 

 attached to the lower border of the tirst two or three caudal vertebrte, 

 thus permitting them to be seen distinctly above, and to the upper bor- 

 ders of the remaining vertebra', thus permitting them to be seen more 

 distinctly beloiv. 



The skin of the two sides of the body unite in such wise as to per- 

 mit a very narrow interval to exist between the two layers. The upper 

 hiyer of the wing membrane is extending directly outward on a level 

 with the back of the chest and of the loin, but the lower layer is vari- 

 able. It may extend outward as in the npper layer, but a disposition 

 exists for it first to conform to the curve of the side of the trunk and 

 join the npper layer near the union of the side with the upper surface 

 of the trunk. In one remarkable instance, Chilonycteris davi/i, the 

 under layer extends quite to the middle line of the back, and thence is 

 deflected in an acute angle outward to join the upper layer. The re- 

 gion of the axilla is greatly depressed in bats, owing to the inclination 

 for the under skin layer to extend upward and backward. This space 

 is so large as to suggest the adaptation of the pouch thuy formed for 

 the protection of the young. In Chciromeles it nuist have another sig- 

 nificance, since it here constitutes a huge b:ig-like involution which 

 extends as far as the middle line of the back. 



IIIE WING MEMBRANE AT REST. 



The bat when at rest folds the fingers by a movement of the root of 

 the hand (carpus) downward on the wrist end (distal end) of the forearm. 

 This movement is characteristic and when com})leted briugs the fingers 

 in a compact bundle (like the ribs of a closed umbrella) under the fore- 

 arm and parallel to it. The hand is thus tucked up toward the rest of 

 the anterior extremity, and as the forearm (in the same movement) is 

 shari)ly flexed on the arm the entire extremity presents the greatest 

 possible contrast to what it exhibited when prepared for flight. The 

 bat now supports the body in one of two ways. It is prone, i. e., with 

 the front of the body «lownward on the plane of sui)poit, or it is pend- 

 ant, i. ('., hung by the claws of the hind feet. If it is prone the base of 



