206 BULLETIN 144, UNITED STATES NATIONAL MUSEUM 



premolar is normally crowded inward behind cingulum of large 

 premolar. 



Eair. — The ear, as compared with that of Myotis nigricans, is 

 smaller and more narrowed, especially in its upper half. Laid for- 

 ward it extends halfway from eye to nostril as described by Thomas. 

 We have examined skins only, and in two of these when thoroughly 

 relaxed the conditions in this respect appear to be about as in the 

 type. Tragus not noticeably different from that of M. nigricans. 



Wing and membranes. — The wing membrane, so far as can be 

 judged from relaxed sldns, is unusually narrow at the level of the 

 elbow; it is inserted at the ankle as in the North American 3/>/otis 

 grisescens. Third metacarpal falling short of elbow by about 4 mm. ; 

 fourth metacarpal usually a very little shorter than third; fifth ob- 

 viously shorter than fourth and usually about 2 mm. shorter than 

 third. Occasionally the fourth equals the third and in a few speci- 

 mens the gradations from third to fourth and from fourth to fifth 

 are equal. Membranes essentially naked throughout; on the basal 

 portion of the uropatagium a few scattered hairs can be detected 

 with the aid of a lens. 



Foot. — The foot resembles that of Myotis nigricans. Calcar 

 usually with a small keel. The ratio of foot to tibia in three speci- 

 mens from Brazil averages 49.4. In the other material examined 

 the proximal end of the tibia has been cut off. 



Fur and color. — Fur everywhere short and woolly, without differ- 

 ences of texture on different parts of the body and with no long 

 hairs on the back or elsewhere. At middle of back the hairs 

 are about 3.5 mm. in length; those of belly are slightly shorter. 

 The fur is strictly confined to the body, not extending out on any of 

 the membranes. Two color phases are represented in the series of 

 skins. The red phase is the more usual (13 out of 16 skins) . In it the 

 color is nearly the ochraceous-taAvny of Ridgway, slightly paler, 

 approaching yellow ocher on the underparts, the hairs without darker 

 bases and without conspicuous gloss. In the brown phase the general 

 color is nearl}^ Mars-brown, the underparts with a slight ochraceous 

 cast, the hairs of the posterior half of back with faintly contrasted 

 paler tips which give to the fur a slight " watered " appearance. 

 Ears and membranes in both phases blackish. 



Skull. — The skull is about the same general size as that of Mijotis 

 albescens, the brain case is similarly high, and the rostrum short (as 

 compared with M. nigincans and M. chiloensis). But here the 

 resemblance ceases. The brain case of M. albescens is unusually 

 smooth, with at most a slightly indicated sagittal crest; that of 

 M. simus is marked by better developed sagittal and lambdoid crests 

 than any other known South American member of the genus. In 

 Myotis albescens the rostrum tapers noticeably forward, so that the 



