172 BULLETIN 43, UNITED STATES NATIONAL MUSEUM. 



fiftli. The fur on the venter is slightly lighter in tint, that of the chest 

 being a shade darker than that of the abdomen. But, on the whole, 

 the dorsum and venter may be said to be of the same general tint. The 

 eiidopatagium is without a naked space alongside the body. 



The keel of the auricle does not project outward beyond the anti- 

 tragus. The manner of termination of the outer margin of the auricle 

 on the antitragus is not described by authors. Judging from Dobson's 

 figure (PI. XXII, Fig. 6), the margin reaches the outer surface of the anti- 

 tragus, while in the N^evada specimen it ends on the middle of the ex- 

 ternal basal process. The outer margin of the auricle is uniformly 

 rounded. 



The American species of Nyctinomus are not variable to any marked 

 degree, and the characters Just given are of greater significance than 

 would be the case in some other genera. But the variations in the 

 form of the tragus in Chiroptera are always associated with other char- 

 acters ; that is to say, the form of the tragus is an index to variation. 

 The slightest modification in outline from the one accepted as typical 

 of the species is associated with some other minor changes in the gen- 

 eral periphery. Kespecting the color, it may be said that the mouse 

 tint of the Nevada specimens is not described in any S])ecies of Nycti- 

 nomus, and is therefore probably not a variation in the color of iV. 

 macrotis. 



Bescrlption. — Muzzle with sharply defined upper borders, with deep 

 emargination between them. The border furnished with numerous 

 pectinate spines, except over the nostrils, where their i^lace is taken 

 by minute papilhe. In the younger of the two specimens the muzzle 

 presents a few scarcely discernible spines on upper border. Vertical 

 ridge on front of muzzle papillate; in general character as in N. hra- 

 siUensis; well defined ridge on mentum ; no submental wart apparent, 

 but a single long hair grows from the center. The ears are thin, semi- 

 translucent, united by a band 1""'" high, and a faint ridge extends 2""° 

 in front of commissure. Three small spines are seen on the internal 

 border. The keel is 9'" long, folded back, and of the same consistence 

 as rest of the auricle; four minute spines are seen on the upper border 

 of the auricle. A faint, shallow scalloj) is seen where the revolute 

 flange of the auricle is defined. The antitragus is broader than high, 

 4""" at base, 2""" high. The notch back of it reaches to the base of the 

 antitragus. The inferior extremity is well defined on the venter, that 

 is to say, that the pubo-tibial fold is absent. 



The second phalanx of the fourth finger is 2""" long. In this regard 

 iV. macrotis resembles N'. megalotis and N. gracilis; and is distinguished 

 from JV. hrasiliensis, in which this phalanx is 7'"'" long. With Old 

 World forms comparisons may be made with N. 2nimili(s and iV. afri- 

 canus, in both of which this phalanx measures 7""" in length. 



The entopatagium with coraco-brachialis fascicle dividing at upper 

 third of membrane, its anterior division reaching line of elbow and 



