66 Bulletin American Museum of Natural History [Vol. XLVII 



direct comparison of the Congo series with four topotypes 1 of citrinus 

 also collected by Mr. Bates. As shown in the accompanying tabulated 

 measurements, A. b. citrinus exceeds A. b. chapini in total length by 

 about 50 mm., and about the same in head and body length, while there 

 is very little difference in the length of the tail. (It is probable that these 

 latter measurements were not taken by the same method in the 

 two cases.) In skull length citrinus exceeds chapini by about 4 mm., 

 with the other skull measurements proportionately different. The 

 'mpression given by comparison of the two series is a greater size differ- 

 ence than the measurements indicate, the citrinus skulls being more 

 heavily ossified, with stronger ridges for muscular attachment in skulls 

 of equal age than is the case in chapini. The color differences are strongly 

 marked. The "ochraceous olive" or " citrine drab" effect above in 

 citrinus is replaced by light clear gray, or slightly yellowish gray, in 

 chapini, with a corresponding difference in the tone of the median dorsal 

 band ; below the ferruginous tone is much darker in the former, approach- 

 ing chestnut-red on the throat and median line in citrinus in place of 

 orange-rufous in chapini. 



The series of 14 specimens of A. b. chapini presents the usual wide 

 range of individual variation in both size and coloration. The smallest 

 specimen in cranial measurements is a female (skull, 51.8 X 32.9) in 

 which all the cheek-teeth have attained full development but are un- 

 worn; in external measurements it is the largest of the females except 

 one, which is much the largest specimen of the entire series (skull, 58.5 X 

 36 . 8) in both external and cranial measurements. 



The color above varies from clear light gray to yellowish gray, and 

 the rufous dorsal line is in some weakly developed or nearly obsolete, 

 in others heavy and continuous from the crown to the hips. The broad 

 rufous zone of the median underparts likewise varies greatly in extent 

 and intensity — from orange-rufous to dark ferruginous, and the adjoin- 

 ing lateral parts from ochraceous orange to pale buff. Young specimens 

 are much paler below than the adults. The white crown spot is nearly 

 always plainly distinguishable and usually forms a distinct mark which is 

 occasionally conspicuous. In one specimen it is a transversely-oval 

 patch, 15 X 25 mm. in area. There is apparently no sexual difference in 

 size or color. 



borrowed from the United States National Museum through the kindness of Air. G. S. Miller, Jr. 

 Curator of Mammals. 



