ALLEN ON THE AMERICAN SC1URI. 



887 



niger has tbe middle of the back nearly black; while that of M chryso- 

 surus appears to be a variety, merely differing in the tail being more 

 rufous" (I. c. p. GG9). There is nothing in Pucherau's description of the 

 last-named species to indicate it is not the young of 8. hoffmanni. 



Judging from what I have seen in other species, the darker color of 

 the lower surface in Alston's 8. rufoniger as compared with S. deppei 

 might result from immaturity ; but in deference to Mr. Alston's opinion, 

 grounded on excellent opportunities for deciding, I give the species pro- 

 visional recognition. 



XVI. SCIURUS PUSILLUS, Geoflroy. 



Sdurus pusillus, "Is. GEOFFROY", DESMAREST, Diet. d'Hist. Nat. x, 1817, 109; Mam. 



1822, 337, pi. Ixxvii, fig. 2. ALSTON, Proc. Zool. Soc. Lond. 1878, 670 pi. xli. 

 Macroxus JcuhU, GRAY, Aun. and Mag. Nat. Hist. 3d ser. xx, 1867, 433. 



NOTE. These names the first with a query, the second unhesitat- 

 ingly I referred in my monograph to 8. cestuans, influenced mainly by 

 the strong aspect of immaturity presented by a specimen in the Museum 

 of Comparative Zoology, which undoubtedly represents this species, not- 

 withstanding the statement by Bnffoti, quoted by me, that the type of 

 the species was shown by the sexual organs to be adult. Although Mr. 

 Alston was unable to find the type of Geoffroy's 8. pusillus, he seems to 

 have established its distinctness from S. cestuans by finding two upper 

 premolars in the British Museum specimens bearing that name, tie 

 considers Gray's M. Jcuhli (which I treated also as the young of 8. cestuans) 

 as unquestionably identical with 8. pusillus. This is apparently a very 

 rare species, as I have met with references to not more than half a dozen 

 specimens in all. It is by far the smallest American species of Sdurus. 



The subjoined summary indicates the changes in nomenclature here 

 made from that adopted in "Monographs of North American Rodents", 

 and also that employed by Mr. Alston in his recent paper " On the 

 Squirrels of the Neotropical Region": 



