Echinomys cajennensis [Winge], 1888, Jordfundne og nulevende Gnavere (Rodentia), E Museo Lundii, Kjöbenhavn, 1(3):71, pl. 6, figs. 5-6, pl. 7, fig. 1.
Proechimys setosus [Thomas], 1921, Ann. Mag. Nat. Hist., 8 (ser. 9):141.
Proechimys elegans [Tate], 1935, Bull. Amer. Mus. Nat. Hist., 68(5):400; [Ellerman], 1940, The families and genera of living rodents, Brit. Mus. (Nat. Hist.), 1:119.
Type locality.—Lagoa Santa, Nova Lima, Minas Gerais, Brazil. Type: Syntypes in Universitets Zoologiske Museum, Kjöbenhavn; collected by P. W. [Lund].
Range.—Known only from the type locality.
Diagnosis.—Aristiforms wide; P4 usually with two counterfolds; M3 sometimes with two counterfolds; p4 with two counterfolds anterior to main fold.
Pelage.—Aristiforms on middorsal region: Gray basally, gradually blackening toward tip; total length, 18 to 20 mm; maximum width, 0.7 mm. Aristiforms on outer thighs: Gray basally, gradually blackening toward tip which is Cinnamon; total length, 15 to 17 mm; maximum width, 0.3 mm. Setiforms on middorsal region: Whitish basally, gradually blackening toward tip, but interrupted by Cinnamon, subapical zone; total length, 17 to 19 mm; maximum width, 0.04 mm. Setiforms on outer thighs: Whitish basally, gradually blackening toward tip but interrupted by near (15"a) Cinnamon, subapical zone; total length, 10 to 12 mm; maximum width, 0.03 mm.
Skull.—Short; rostrum short but not stout; length of nasals 17 mm; bullae large, smooth, and well-inflated; jugals with conspicuous, transverse ridge; postorbital process of zygoma long, spiniform and constructed entirely of jugal; incisive foramen narrow (4 × 1.7 mm); vomerine sheath complete and slender; posterior palatine foramina obsolete; mesopterygoid fossa extending anteriorly as far as middle parts of second molars.
Teeth.—Incisors orthodont. P4 usually with two counterfolds, rarely with three; upper molars with only one counterfold, but M3 sometimes with two, posterior one being vestigial. Lower molariform teeth: p4 with two counterfolds, both being anterior to main fold; molars with only one counterfold.