Teeth.—Upper molariform teeth with three counterfolds; p4 with four counterfolds; m1-3 with three counterfolds.
Comparison.—From P. g. oris, nesiotes differs in: Aristiforms conspicuously wider; incisive foramen shorter and narrower, with borders parallel instead of posteriorly constricted; posterior margin of incisive foramen farther from premolars; p4 with four, instead of three, counterfolds; lower molars with three instead of two counterfolds. From P. g. leioprimna, nesiotes differs in: Incisive foramen with parallel borders instead of oval; p4 with four instead of three counterfolds; m3 always with three instead of two counterfolds.
Remarks.—Dr. E. Snethlage mentions the type as having been collected at night in the forest.
Specimens examined.—Total number, 8 (MCZ, CNHM, MN), from Brazil, Pará, Tocantins River, Ilha de Manapirí.
Proechimys guyannensis leioprimna subspecies nova
Type locality.—Cametá, left bank of Tocantins River, near its mouth, Cametá, Pará, Brazil. Type: Chicago Natural History Museum, no. 19503, adult female; collected on 21 January, 1911, by Dr. Emilia Snethlage; original number, 35.
Range.—Known only from type locality but probably extending westward toward Xingú River.
Diagnosis.—Aristiforms wide and stiff; general color on upper parts Ochraceous-Orange, incisive foramen moderately long; oval; vomerine sheath complete; all molariform teeth with three counterfolds, except lower, third molar which has only two.
Pelage.—Aristiforms on middorsal region: Gray basally, gradually blackening toward tip which is extended as a short filament; total length, 19 to 21 mm; maximum width, 0.8 to 1 mm. Setiforms on middorsal region: Whitish basally, gradually blackening toward tip but interrupted by Ochraceous-Orange, subapical zone 2 to 3 mm long; total length, 17 to 20 mm; maximum width 0.1 mm. Setiforms on outer thighs: Whitish basally, becoming gradually gray and then blackish toward tip but interrupted by Ochraceous-Buff, subapical zone; blackish tip short; total length 13 to 15 mm; maximum width 0.06 mm.