ALLEN: MAMMALS FROM THE BLUE NILE VALLEY. 353 



size, the skull is longer, •with a larger rounder braincase, which is less 

 markedly truncate at the lambdoid crest, in contrast to that of emini 

 which is almost squarely truncate in posterior outline. In C. pumilus 

 the lambdoid ridges are not transverse but are directed slightly for- 

 ward so that they do not form the posterior boundary of the skull as 

 in these two species, and the supraoccipital is not hidden by them in 

 dorsal \dew. The skull of C. himttatus (no. 14,456) measures: — 

 greatest length 21 mm., palatal length 8.5, zygomatic breadth 12.5, 

 width outside last molars 9.1, interorbital constriction 4.2, upper 

 tooth row excluding incisors 7.5, lower tooth row excluding incisors 8. 

 In one of the two specimens, the minute first upper premolar is 

 nearly in the tooth row, but very slightly exterior to the posterior heel 

 of the canine; in the other the same tooth is entirely external to the 

 tooth row and placed in the external angle between the canine and the 

 second premolar, which are actually in contact on each side. Some- 

 what similar variation has just been noted in case of C. emini, and is 

 evidently an expression of the tendency toward shortening the tooth 

 row through the displacement and eventual loss of the minute first 

 premolar. 



Chaerephon pumilus (Cretzschmar). 

 Lesser Free-tailed Bat. 



Dysopes pumilus Cretzschmar, Rlippell's Atlas reise nordlichen Afrika. 

 Saugeth., 1826, p. 69, pi. 27, fig. a. 



Several specimens of this bat were obtained along the Blue Nile at 

 El Garef and Magangani where they seemed to be common. They 

 appeared shortly after dusk, flew rather high and swiftly. This 

 species is dichromatic and presents a russet and a blackish or dark 

 chocolate-brown phase. The former condition seems to be due to a 

 lack of the blackish pigment in the hairs; the latter to the mixture of 

 the reddish and the blackish pigments which commonly coexist in the 

 pelage. The extreme tips of the hairs are pale, giving a faintly hoary 

 aspect to the back. The lower surfaces are paler than the upper and 

 along the sides of the body from the axilla to the groin is a pale, almost 

 whitish band of fur on the wing-membranes, that contrasts with the 

 darker sides of the body. These details of color have not heretofore 

 been described, no doubt because they are not very apparent in alco- 

 holic specimens. The original description was based on a specimen 

 from the Red Sea coast at Massowa, collected by Riippell. The 

 forearms of the five specimens obtained measure from 35.5 to 37.5 mm., 



