_Teeth._--Upper molariform teeth with two counterfolds; these completely separated in 3 of 16 specimens; two counterfolds coalesced in all three molars in 6 specimens; counterfolds coalesced in only two molars in 3 specimens; counterfolds coalesced in only one molar in 4 specimens. Lower molariform teeth with two counterfolds which are completely separated in 13 of 16 specimens; counterfolds coalesced in only one molar in 2 specimens; counterfolds coalesced in all three molars in one specimen. _Comparisons._--From _P. i. gratiosus_, _bonafidei_ differs in: Aristiforms wider; tail shorter; molariform teeth with two counterfolds instead of one or two. Differences from _P. i. iheringi_ are given in the account of that subspecies. _Remarks._--Of females with embryos two were captured in April and one in September. The embryos number 2, 1, 2. Young were captured mostly in April, but two were taken in July. Male gonads seemed to be most active in March, April and September. The animals lived in a second growth forest, approaching the climax. The rainfall was more than 1600 mm annually, and the mean annual temperature was 18.5° centigrade. _Specimens examined._--Total number, 18 (MN), from Brazil, Rio de Janeiro, _Teresópolis_, Fazenda Bõa Fé. =Proechimys iheringi gratiosus= subspecies nova _Type locality._--Floresta da Caixa Dagua, _Santa Teresa_, Espirito Santo, Brazil; altitude 750 meters. _Type_: Museu Nacional, no. 4024, adult male; collected on 25 May, 1940, by C. Lako; SEPFA no. M 6911. _Range._--Known only from the type locality. _Diagnosis._--Aristiforms narrow; tail of same length as head and body; setiforms Ochraceous-Buff; incisive foramen long; vomerine sheath usually incomplete; upper molariform teeth with one or two counterfolds; lower molariform teeth with two counterfolds, except that m3 usually has only one. _Pelage._--_Aristiforms on middorsal region_: Gray basally, gradually blackening toward tip; total length, 21 to 27 mm; maximum width, 0.6 mm. _Aristiforms on outer thighs_: Gray basally, gradually blackening toward middle, and Ochraceous-Buff on distal half; total length, 18 to 21 mm; maximum width, 0.5 mm. _Setiforms on middorsal region_: Gray basally, gradually blackening toward tip but interrupted by short, Ochraceous-Buff, subapical zone; total length, 18 to 20 mm; maximum width, 0.06 mm. _Setiforms on outer thighs_: Gray basally, gradually blackening toward middle, and distal part Ochraceous-Buff or with only tip blackened; total length, 14 to 16 mm; maximum width, 0.05 mm.