Skull.—Large, with elongate rostrum; bullae large and well inflated; jugals with transverse ridge inconspicuous; postorbital process of zygoma small, formed mostly by squamosal; incisive foramen elongated (5.5 × 2.5 mm); vomerine sheath incomplete or, if complete, with maxillary part thin and delicate; posterior palatine foramen at plane of first molars; mesopterygoid fossa extending forward as far as middle parts of second molars.
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.