178 Bulletin American Museum of Natural History. [Vol. XXXIV, 
Premolars, ?; mammee, 6. (For description see p. 188.) 
- Range, western Andean region, south to Peru and Bolivia, north to 
central Costa Rica. About 20 species and subspecies. 
Sciurillus Thomas, 1914 (genus, referred to Nannosciurine). Type, 
by original designation, Sciwrus pusillus Desmarest. (For description 
see p. 196.) 
Premolars, ?; mamme, 6 (?). 
Range, the Guianas. One species, with subspecies. 
Leptosciurus gen. nov. (for description see p. 199). Type, Scrurus rufo- 
niger Pucheran, not of Gray = Funambulus pucheranw Fitzinger. 
Range, Andean Region of Colombia, and portions of Peru and Bolivia. 
Three species, several subspecies. 
Notosciurus Allen, 1914. Type, by original designation and monotypy, 
Notosciurus rhoadsi Allen. (For description see p. 209.) 
Range, Ecuador. Known only from the type specimen. 
Mesosciurus gen. nov. (for description see p. 212). Type, Sciurus 
estuans var. hoffmanni Peters. 
Premolars, +; mamme, 6. 
Range, northeastern Nicaragua, northern border of South America, and 
the Andean region south to Ecuador. Numerous species and subspecies. 
Histriosciurus (subgen. nov. of Mesosciurus Os pp. 213,:236)). . Type, 
Sciurus gerrardt Gray. 
Range, western and northern coast regions of Colombia. 
Guerlinguetus Gray (subgenus of Sciurus). Type by tautonymy, 
— Scturus guerlinguetus Gray = Sciurus estuans Linné. (For description see 
p.. 254.) 
Premolars, +; mamma, 8. 
Range, the Guianas, west to the Orinoco, the lower Amazon, and 
eastern Brazil. About 5 species and subspecies. 
Hadroscvurus gen. nov. (for description see p. 265). Type, Sciurus 
flammifer Thomas. 
Premolars, ¢; mamme, 8. 
Range, Caura district, Rio Orinoco. Known only from the type species. 
Uroscvurus gen. nov. (for description see p. 267). _ Type, Sciurus tricolor 
Poeppig. 
Premolars; t mamme, 8. 
Range, basin of the Amazon. About 5 species, with numerous subspecies. 
Simosciurus gen. nov. (for description see p. 280). Type, Sciurus 
stramineus Eydoux and Souleyet. 
Premolars, + ; mamme, 8. 
Range, southwestern Ecuador and northwestern Peru. One species, 
with several subspecies. 
