884 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



S.fraseri, and their allocation here is on his authority. It turns out 

 that the Guyaquil specimens of iny S. hypopyrrhus series (one of which 

 Mr. Alston has seen) represent this species. Mr. Alston states that this 

 species is rare in collections, and appears to be the only representative of 

 the genus in Western Peru. He further says : "A remarkable peculiar- 

 ity of this species is its tendency to the development of irregular tufts 

 of pure white hairs, rather longer than the rest of the fur, and some- 

 times uniting in large patches. These asymmetrical markings are pres- 

 ent in the majority of the individuals examined." This peculiarity in 

 the texture and color of the pelage I looked upon as abnormal and as 

 indicating a tendency to albinism, and am surprised that it should prove 

 of such general occurrence. 



XL SCIURUS VAKIABILIS, Is. Geoffroy. 



Sciurus variabilis, Is. GEOFFROY, Mag. de Zool. 1832, i, pi. iv. 



Sciurus langsdorffi, BRANDT, Me"m. Acad. de St. Pe"tersb. 6 e s6r. Math. Phys. et Nat. iii, 



2 e pt. 1835, 425, pi. xi. 



Sciurus igniventris, "NATTERER", WAGNER, Wiegm. Arch, liir Naturg. Ib42, i, 360. 

 Sciurus pyrrhonotus, "NATTERER", WAGNER, Wiegm. Arch, fiir Naturg. 1842, i, 360. 

 Sciurus tricolor, "PoppiG", TSCHUDI, Faun. Peruan. 1844-46, 156, pi. xi. 

 Sciurus mono, WAGNER, Abb. Bayer. Ak. v, 1 50,275. 

 Macroxus gerrardi, GRAY, Proc. Zool. Soc. Lond. 1861, 92, pi. xvi. 



Sciurus brunneo-nigw, '* CASTLENAU ", GRAY, Ann. and Mag. Nat. Hist. 3d ser. xx, 1867, 429. 

 Sciurus fumigatus, GRAY, Ann. and Mag. Nat. Hist. 3d ser. xx, 1867, 428. 

 Sciurus varialilis and S. gerrardi, ALLEN, Mon. N. Am. Rod. 1877, 768, 766. 



NOTE. Mr. Alston extends this species to cover my 8. gerrardi, which 

 I separated mainly on the ground of smaller size. He says : " Here, 

 again, the greater amount of material compels me to go beyond Mr. 

 Allen in the identification of nominal species. Most of the above syn- 

 onyms were brought together by him under the name of S. variabilis ; 

 but 8. gerrardi and 8. rufo-niger [lege brunneo-niger] were kept separate 

 under the former title. The principal points on which he rested were 

 the smaller size and shorter ears of S. gerrardi; but on examination of a 

 sufficient series, I have not been able to find any constancy in the pro- 

 portions of the ears, while the difference in size totally disappears. 

 . . . The smaller specimens (8. variabilis, 8. gerrardi, etc.) appear to 

 prevail towards the north j but this is not constant. . . . Kor is it 

 constantly connected with any of the numerous varieties of coloration 

 rufous, grizzled, and melanistic specimens occurring of all sizes." These 

 color-variations, he says, seem to resolve themselves into three primary 

 groups, namely : "1, the morio type", melanistic; " 2, the variabilis 

 type", red, varied with black : " 3, the langsdorffi type ", reddish- or yel- 

 lowish-grizzled. Each of these types seems to prevail in certain locali- 

 ties, but there is no regularity in their distribution, the red and grizzled 

 often occurring together. 



Our synonymy of this variable group agrees, except that I included 

 8. stramineus under variabilis^ and Gray's Macroxus xanthotus under 

 8. gerrardi, which latter Mr. Alston refers to 8. griseogenys ( = Sciurus 



