152 Bulletin American Museum of Natural History. [Vol. XXXIV, 
pusillus Desmarest, 1817, based on Le petit Guerlinguet of Buffon, from 
Cayenne. No other species was described till 1832, when Is. Geoffroy 
described and figured Scrwrus variabilis, based on specimens supposed to 
have come from northern Colombia. The name has since been applied 
indiscriminately by authors to the large white-bellied red-backed squirrels 
of South America of which there are several species, some of which have 
no close interrelationship. As the description and figure are contradictory, 
_and neither agrees well with any squirrel at present known, the name is here 
treated as unidentifiable. 
In 1853 Brandt described Sciurus langsdorffiit, from “ Brasilia’? — the 
first of various forms of the large bushy-tailed squirrels peculiar to the 
great Amazonian drainage basin to be made known, and the fourth recog- 
nizable species of South American squirrel described up to this date. 
In 1842 Wagner described Sctwrus igniventris and S. pyrrhonotus, respec- 
tively from the Upper Rio Negro and the mouth of the Rio Madeira, both 
belonging to the langsdorffit group, which latter name (in 1850) he restricted 
to the form from Cuyubé, Matto Grosso. In 1843 he added Sciurus gilvi- 
_ gularis, from near the mouth of the Rio Madeira — a small species resem- 
bling S. estwans in size and in coloration, to which it was generally erroneously 
referred for the next fifty years. Wagner’s three species were all based on 
Natterer’s collections. 
In 1844 Sccwrus stramineus was described and figured by Eydoux and 
Souleyet, a large squirrel from southwestern Ecuador. About the same 
time Poeppig (in Tschudi’s ‘Fauna Peruana’) described Sciurus tricolor, 
the largest of all the South American squirrels. In 1845 Pucheran described 
two small squirrels from Santa Fé de Bogota, Colombia, as, respectively, 
Scirus rufoniger and Sciurus chrysuros, the relationships of which have 
only recently been determined, the names, when used, having been usually 
grossly misapplied. Only one other species was described for the next ten 
years, namely, Sczwrus nebouxt I. Geoffroy, from northwestern Peru, a form 
closely related to S. stramineus, to which it is now referred as a subspecies. 
This brings the number of species of South American squirrels described 
prior to 1856 to 13, representing 11 valid forms, one being unidentifiable 
and another a synonym. No more were added till 1867, when J. E. Gray 
published his ‘Synopsis of American Squirrels’ (Ann. and Mag. Nat. Hist. 
(3), XX, pp. 415-484, Dec. 1867). In this paper he described 18 species 
as new, of which 9 were from South America and 9 from Mexico and Central 
America. Of those described from north of the Isthmus of Panama only 
3 are now regarded as valid forms, the others being synonymized with 
previously described species. Of the 9 South American species 4 are given 
recognition as species or subspecies in the present paper, 4 are assigned to 
