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.
Skull.—Slender; nasals short; bullae large and well-inflated; jugals with conspicuous transverse ridge; postorbital process of zygoma conspicuous, spiniform and formed almost exclusively by jugal; incisive foramen elongated and narrow (5 × 1.8 mm); vomerine sheath complete and formed almost exclusively by premaxillae; maxillary part of this sheath short and in most specimens the two parts of sheath completed by vomer itself; mesopterygoid fossa extending forward as far as middle of second molars and in some skulls as far as anterior border of second molars; posterior palatine foramina at anterior plane of first molars.