Skull.—Slender; bullae small and well inflated; jugal dorso-ventrally wide with transverse ridge inconspicuous; incisive foramen short, 3.5 × 2.5 mm; vomerine sheath complete; mesopterygoid fossa extending forward as far as middle parts of second molars; postorbital process of zygoma small, formed by both jugal and squamosal; posterior palatine foramina at plane of premolars; interorbital breadth narrow.
Teeth.—Upper molariform teeth with two or three counterfolds (when unworn usually three and rarely four); sometimes only one counterfold in M3 and sometimes counterfolds fused in molars. Lower molariform teeth with two counterfolds, rarely one in m3.
Comparisons.—From P. i. bonafidei and P. i. gratiosus, iheringi differs in: Incisive foramen shorter; vomerine sheath complete, instead of usually incomplete; setiforms Cinnamon-Buff, instead of Ochraceous-Buff; upper molariform teeth with two or three separate counterfolds, instead of having counterfolds fused or reduced to one or two; aristiforms narrower in iheringi than in bonafidei.
Specimens examined.—Total number, 25, from Brazil, as follows: São Paulo, Formosa, Ilha de São Sebastião, 9 (DZ 6, MN 2, MCZ 1); São Paulo, Mogi das Cruzes, Alto da Serra, alt. 900 m., 2 (DZ); São Paulo, Ubatuba, alt. 10 m., 4 (2 DZ, 2 MN); Rio de Janeiro, Angra dos Reis, 2 (MN); Rio de Janeiro, Angra dos Reis, Ilha Grande, 7 (5 DZ, 1 MCZ, 1 MN).
Proechimys iheringi bonafidei subspecies nova
Type locality.—Fazenda Bõa Fé, Teresópolis, Rio de Janeiro, Brazil; alt. 850 meters. Type: Museu Nacional, no. 6183, adult male; collected on 18 August, 1942, by G. Pereira; SEPFA no. M 14663.
Range.—Known only from the type locality.
Diagnosis.—Aristiforms wide and stiff; tail shorter than head and body; setiforms Ochraceous-Buff; incisive foramen long; vomerine sheath incomplete, or rarely complete; molariform teeth with two counterfolds usually fused.
Pelage.—Aristiforms on middorsal region: Gray basally, gradually blackening toward tip; total length, 22 to 26 mm; maximum width, 0.8 mm. Aristiforms on outer thighs: Gray basally, gradually blackening toward tip but interrupted by Ochraceous-Buff subapical zone; some Ochraceous-Buff to tip; total length, 18 to 20 mm; maximum width, 0.7 mm. Setiforms on middorsal region: Gray basally, gradually blackening toward tip but interrupted by Ochraceous-Buff, subapical zone; total length, 17 to 20 mm; maximum width, 0.06 mm. Setiforms on outer thighs: Gray basally, gradually blackening toward tip but interrupted by Ochraceous-Buff, subapical zone; only a short blackened tip.