302 BULLETIN UNITED STATES GEOLOGICAL SUEVEY. [Yol.TI. 



In 1867* J. E. Gray published a revision of Sciurus and of the genera 

 which late writers have dismembered therefrom. But this article, in 

 which the author very briefly describes numerous new species and pro- 

 poses to name a number of subgeneric and other groups, is marred 

 {entache, soiled) by the defect inherent in nearly all the productions of 

 this celebrated zoologist, the characters of his groups and subgenera 

 being for the most part imaginary, so that species could be named which 

 figure at the same time in two or three different sections under as many 

 different names. 



Among the most important and durable works are those which J. A. 

 Allen t and E. E. Alston | have bestowed upon the squirrels of the two 

 Americas. These writers enable us to reduce the number of well-de- 

 fined species to 15, from upwards of 40 admitted by Gray in 1867. 



The Asiatic Squirrels have latterly been the subject of works of the 

 same kind. Schlegel, A. Milne-Edwards, || and Anderson § have shown 

 the number of species to be far too large, and that the greater part of 

 them were only based on the variations in pelage, often of great extent, 

 which certain species present according to changes of season — variations 

 observed in a general way throughout the genus, but which are more 

 strongly pronounced in the species of Southern Asia and Malasia. 



Such variations are in fact only an exaggeration of those known to 

 occur in our European squirrel, 8. vulgaris, of which the Siberian Petit- 

 gris, the dark-colored 8. alpinus of mountainous regions, and the tawny 

 S. persicus of Asia Minor, are only seasonal or local varieties. The 

 squirrels of tropical regions, especially in Asia, present extremely curi- 

 ous transition states of pelage {livrees de passage), the analogues of which 

 are scarely to be found except among birds, but which have neverthe- 

 less given rise to many nominal species. Thus the several striped-flanked 

 squirrels {Ecureuils a flancs rayes, 8. rafflesi, &c.), described as so many 

 distinct species, only represent individuals in change of pelage of the 

 single species for which the name ;S^. prevosii Desm. should be retained. 

 Previous to Gray's work, the French zoologist, Paul Gervais, had shown fl 

 that the form of the skull, with some other secondary characters, enables 

 us to distinguish in 8ciurus several small groups which correspond quite 



Huet, assistant naturalist of the Museum, published in the Archives of that establish- 

 ment (new series, vol. iii, p. 131, 1880), under the title of "Recherches sur les Ecu- 

 reuils africaines," a monograph based on the national zoological collections. This 

 important work meets the want we expressed in saying that our classification of the 

 Airican species could only be provisional, until they should have been properly mono- 

 graphed." The modified synopsis of African Squirrels and their allies, which the 

 author is led to give in consequence of M. Huet's researches, is in the present trans- 

 lation substituted for the original text. — C] 



*Anu. Mag. Nat. Hist., 3d ser., xx, pp. 270, 323, 415, 434. 



tP.Z.S., 1878, p. 656. 



tMonogrs. N. A. Rodentia, 1877; Bull. U. S. Geol. & Geogr. Surv., iv, No. 4, 1878, p. 

 877. 



II Bull. Soc. Philom., 1877, p. 16. 



§ Anat. and Zool. Researches (Exped. to West Yunnan), 1878, p. 214, et seq. 



H Mag. de Zool., 1842, pp. 1-7. 



