_Skull._--Strong, with jugals dorso-ventrally wide; interorbital region and cranium wide; bullae well inflated; transverse ridge of jugals not well-developed; postorbital process of zygoma small and formed only of squamosal; incisive foramen 4.7 × 2.2 mm; vomerine sheath always incomplete, with maxillary part reduced to small process; mesopterygoid fossa extending forward as far as middle of second molars or only slightly short thereof; posterior palatine foramina at plane of front of first molars. _Teeth._--All upper molariform teeth with two counterfolds in 4 specimens; one having only one counterfold in M3; 3 with counterfolds coalesced in one or two molars. Lower molariform teeth with two counterfolds in one specimen, these counterfolds not coalesced; m3 with one counterfold in 4 specimens and with two in one specimen. _Comparisons._--Differences from _P. denigratus_ and _P. i. paratus_ are given in the accounts of those animals. _Specimens examined._--Total number, 5 (MN), from Brazil, Espirito Santo, _Colatina_, Campinho; altitude 500 meters. =Proechimys iheringi denigratus= subspecies nova _Type locality._--Mata do Ribeirão da Fortuna, 40 kilometers west of Ilheus, _Itabuna_, Bahia, Brazil. _Type_: Museu Nacional, no. 8500, adult male; collected 16 March, 1945. _Range._--Known only from the type locality. _Diagnosis._--Aristiforms wide and stiff; tail longer than head and body; setiforms near (15''_a_) Cinnamon; incisive foramen long and narrow; vomerine sheath complete; premolars with two counterfolds, upper molars with one or two, and lower molars with only one. _Pelage._--_Aristiforms on middorsal region_: Gray basally, gradually blackening toward tip; total length, 20 to 22 mm; maximum width, 1.1 mm. _Aristiforms on outer thighs_: Gray basally, gradually blackening toward tip or with distal part near (15''_a_) Cinnamon; total length, 14 to 16 mm; maximum width, 0.5 mm. _Setiforms on middorsal region_: Gray basally, gradually blackening toward tip but interrupted by near (15''_a_) Cinnamon, subapical zone 4 mm wide; total length, 18 to 20 mm; maximum width, 0.05 mm. _Setiforms on outer thighs_: Gray basally, gradually blackening toward tip but interrupted by wide, near (15''_a_) Cinnamon, subapical zone.