The receipt of more than thirty specimens of this rare genus of squirrels from native field collectors working in Brazil for the American Museum has prompted us to go over the rather scanty literature and survey the status of Sciurillus.

A South American pygmy squirrel was definitely described by Buffon (1789) under the name “le petit guerlinguet,” and by Desmarest (1817) it was given the technical specific name pusillus and placed in the blanket genus Sciurus.

No further constructive mention of the animal appeared for half a century until Gray (1867) redescribed pusillus (he had a specimen in the British Museum), described Macroxus kuhlii (based upon a specimen purchased by the British Museum with the Castelnau collection), and transferred pusillus Desmarest to Macroxus. A decade later Allen (1877) concluded, not solely from the literature, that pusillus and kuhlii were not only synonymous with one another but merely juveniles of aestuans.