_Remarks._--This subspecies shows greater variability than any other in this species. There are two types of coloration. The most common type of coloration is dark, with Tawny, subapical zones in the setiforms of the middorsal region and many completely black setiforms; in the other type the subapical zone is still Tawny but there are no black setiforms. One specimen from Obidos, on the north bank of the Amazon, completely agrees in the characteristics of color and skull with the reddish type and suggests either that there is an extension of the range of the subspecies along the lower course of the Tapajoz or that there are two subspecies, in which event the animals from Tauarí are intergrades between _hyleae_ and an unnamed, tawny-colored subspecies occurring to the southward. Between 13 and 23 January, 1934, A. M. Olalla collected 10 adult females, 6 of which contained embryos. Three of the females had 2 embryos each, two had 3 embryos each and one had only 1 embryo. At this same time and place only ten per cent of specimens obtained were not fully adult. _Specimens examined._--Total number, 21, from Brazil, Pará, as follows: _Porto de Moz_, Tauarí, right bank of Tapajoz, approximately 85 kilometers south of Santarem, 20 (19 MCZ, 1 CNHM); _Obidos_, Obidos, 1 (MCZ). =Proechimys guyannensis nesiotes= subspecies nova _Type locality._--Ilha de Manapirí, Rio Tocantins, Pará, Brazil. _Type_: Chicago Natural History Museum, no. 19496, adult male; collected on 9 December, 1910, by Dr. Emilia Snethlage; original number, 12. _Range._--Known only from the type locality. _Diagnosis._--Aristiforms wide and stiff; general color on upper parts Ochraceous-Orange; incisive foramen long, with parallel borders; vomerine sheath complete and thick; p4 with four counterfolds, remaining molariform teeth with three counterfolds. _Pelage._--_Aristiforms on middorsal region_: Gray basally, gradually blackening toward tip; total length, 18 to 19 mm; maximum width, 0.9 mm. _Setiforms on middorsal region_: Gray basally, gradually blackening toward tip but interrupted by Ochraceous-Orange, subapical zone 4 mm long; total length 16 to 19 mm; maximum width, 0.06 mm. _Setiforms on outer thighs_: Whitish basally, gradually becoming gray and blackish toward tip but interrupted by Ochraceous-Buff, subapical zone 3 mm long; total length, 13 to 15 mm; maximum width, 0.03 mm.