36 BULLETIN 43, UNITED STATES NATIONAL MUSEUM. 



ium are of the colors of the dorsiiui ratlier than the venter.* Imme- 

 diately behind the junction of the ears the head is almost naked. The 

 basal third of the auricle is covered with hair. The external surface 

 of the external basal lobe is entirel}^ clothed. The inner surface of the 

 auricle at the internal basal lobe, and extending thence upward along 

 the inner border, is sparsely covered with short hairs. The proximal 

 half of the humerus is also clothed, as well as the endopatagium, and 

 a line thence to the proximal one-half of the thigh. Elsewhere the 

 membranes are naked, save at the dorsum of the first metacarpal bone, 

 where a few hairs are found. 



Membranes. — In the second interspace of the wing the membrane is 

 attached to the palmar borders of the second and third metacarpal 

 bones; in the third interspace, to dorsal border of the third metacarpal 

 bone and palmar border of the fonrth; and in the fourth interspace, to 

 the palmar borders of Ihe fourth and fifth metacarjia] bones. The 

 calcaro-tarsal expanse is absent. The prebrachium is without distinc- 

 tive lines. Intercostal lines nine in number. Coraco brachialis fascicle 

 does not reach the line of the elbow. At the elbow is a number of tine, 

 radiated lines, apparently due to muscle-fibers. The membrane is 

 slightly thickened near the ankle. Triceps fascicle system made up 

 of two inferior and two superior branches. Vertical muscle lines seven 

 in number. A small thread-like line appears at the proximal third of 

 the fifth metacarpal and passes nearly the entire length of the digit. 

 In the fourth interspace the j)redigital nerve arises from the fifth met- 

 acarpal bone at about its middle; one or two nerves arise from the fifth 

 metacarpophalangeal joint; the post-digital from the nietacarpo-pha- 

 langeal joint; longitudinal line distinct. Thirty-six transverse lines 

 can be counted in the fourth interdigital interspace. These are greatly 

 in excess of ihe number in any other form examined. Both in this space 

 and in the angle between the fifth metacari)al bone and the radius a 

 fine network of fibers is present. No similar appearance is seen else- 

 where. In the third interspace both predigital and post digital nerves 

 arise from the metacarpo-phalaugeal joints; h)ngitudinal line distinct. 



The interfemoral membrane reaches to the ankle. The tail projects 

 one-sixth of its length beyond the inferior margin. An oblique line ex- 

 tends from the end of the second vertebra to the middle of the calcar. 

 The structure last named is one-half the length of the tibia; its tip 

 projects conspicuously from the truncated border of the interfemoral 

 memhi-ane. The terminal cartilage of the third digit acicular; that of 

 the fourth digit is bifid, witii the h)bes equal; while that of the fifth 

 digit, while bifid, exhibits the posterior lobe greatly prolonged. In 

 specimen No. 404 S, I. the ternunal cartilage of the right third digit is 

 composed of four segments. 



*C()ue.s ami Yarrow (Wheeler Exp. Geol. Siirv., Zool, 1875) state that alcohol-bleach- 

 iug causes the ditference between M. californicus and M. iraterhousii. Of this state- 

 ment the authors offer uo evidence. I doubt its correctness. 



