638 THE AMERICAN NATURALIST. (VoL. XXXIII. 
works of previous authors. As a first step to this result he 
identified as far as possible the type localities of all the species 
previously described, and secured from them “‘topotypes”’; and 
he was further greatly aided by Mr. Oldfield Thomas, of the 
British Museum, in determining many of Gray’s imperfectly 
described species. While it is too much to expect that Mr. 
Nelson’s revision will be final, especially as regards the Central- 
American forms, his paper is of the highest importance as a 
contribution towards reducing to comparative order the chaos 
that has hitherto prevailed in this difficult field. As a result 
of his determinations several radical changes of nomenclature 
have been necessary, including the proper allocation of Erxle- 
ben’s Sciurus variegatus, which has proved so great a source of 
trouble to previous writers, but which Mr. Nelson has conclu- 
sively shown belongs, not to any species of Sciurus, but to a 
species of Spermophilus! Great credit is due Mr. Nelson for 
his well-planned and intelligent work in the field, as well as for 
the careful elaboration of his material and the clear and work- 
manlike way in which he has presented his results. 
In addition to Mr. Nelson’s revision of the squirrels of trop- 
ical America, two recent contributions have been made to our 
knowledge of the squirrels of North America north of Mexico. 
In December, 1896, Mr. Outram Bangs published “A Review 
of the Squirrels of Eastern North America,” ! which included 
the flying squirrels as well as the ordinary tree squirrels. This 
paper gave, under the genus Sciurus, four species and six sub- 
species, three of the latter being described as new, to which 
Mr. Bangs has since added another subspecies.” 
The squirrels of western North America have not, as a 
whole, been recently revised, although much has been inci- 
dentally written about them, and several new forms have been 
described. The chickarees, or red squirrels (subgenus Tamia- 
sciurus), were recently monographed by the present writer.? In 
1 Proc. Biol. Soc. Wash., vol. x, pp. 145-167. Published Dec. 28, 1896. 
2 Sciurus a gymnicus, Proc. N. Engl. Zoöl. Club, vol. i, p. 28. Pub- 
pare March 31, I 
Allen, J. A. a. of the Chickarees, or North-American Red Squirrels 
wie Tamiasciurus), Bull. Am. Mus. Nat. Hist., vol. x (1898), pp. 249-298. 
Published July 22, 1898. 
