_Pelage._--_Aristiforms on middorsal region_: Grayish basally, gradually blackening toward tip; total length, 18 to 20 mm; maximum width, 0.8 to 1.0 mm. _Setiforms on middorsal region_: Gray basally, gradually blackening toward tip but interrupted by a light (16 i), Buckthorn Brown, subapical zone 2 mm long; total length, 18 to 22 mm; maximum width, 0.03 mm. Most of them, however, whitish basally, gradually blackening toward tip without any distinctively-colored, subapical zone; total length, 24 to 26 mm; maximum width, 0.5 mm. _Setiforms on outer thighs_: Whitish basally, gradually blackening toward tip but interrupted by an Ochraceous-Buff, subapical zone 3.5 mm long; black tip short; total length, 17 to 19 mm; maximum width, 0.05 mm. _Skull._--Large and slender; rostrum elongate; nasals bluntly pointed posteriorly; supraorbital ridges thick (but not expanded) and extending across parietals but almost obsolete in middle part of parietals; infraorbital foramen with weakly-developed groove for transmission of nerve; postorbital process of zygoma involving mostly squamosal; incisive foramen 5.5 x 2.8 mm wide in anterior third, with margins constricted posteriorly and extending as ridges approximately 2 mm beyond posterior margin of incisive foramen; posterior margin of incisive foramen approximately 2.5 mm anterior to premolars; vomerine sheath complete with maxillary part weak and premaxillary part extending posteriorly beyond middle of incisive foramen; mesopterygoid fossa extending forward as far as middle of M3; bullae well inflated and elongated. _Teeth._--P4 with four counterfolds in one of five specimens and with three in remainder; M1 with four counterfolds in three of five specimens and with three in remainder; M2 with three counterfolds in one specimen and with four in all four remaining specimens; M3 always with four counterfolds. Lower premolars with four counterfolds and lower molars with only three. _Comparisons._--The subspecies is easily distinguishable from _P. s. angularis_ by: larger number of black setiforms on back, forming an almost black longitudinal band; more elongate skull; larger and longer bulla; longer incisive foramen which is more constricted posteriorly. _Specimens examined._--Total number, 6 (AMNH), as follows: Venezuela, territ. _Amazonas_, Esmeralda, Mt. Duida, altitude 325 m., 4; Venezuela, territ. _Amazonas_, Rio Cassiquiare, Quemapuré, 1; Brazil, Amazonas, _São Gabriel_, Rio Uaupés or Caiari, Tatú, 1. =Proechimys semispinosus kermiti= Allen _Proechimys kermiti_ Allen, 30 December 1915, Bull. Amer. Mus. Nat. Hist., 34(22):629 (orig. descr.); Allen, 1916, Bull. Amer. Mus. Nat. Hist., 35(30):569; Tate, 1935, Bull. Amer. Mus. Nat. Hist., 68(5):400; Ellerman, 1940, The families and genera of living rodents, Brit. Mus. (Nat. Hist.), 1:119.