E. Snethlage collected one specimen in a garden (Providencia, E. F. B.). However, according to the personnel of the Brazilian Health Service, the animals are strictly forest dwellers although they do make excursions into more open places. _Specimens examined._--Total number, 3, from Brazil, Pará, as follows: Providencia, E. F. B., approximately 15 kilometers east from Belem, 1 (CNHM); Tanaquará, near Belem, 1 (MN); Rio Guamá, near Belem, 1 (AMNH). _Additional record._--Brazil, Pará, Benevides, E. F. B., approximately 100 kilometers north-east of Belem (Thomas, 1912:89). =Proechimys guyannensis arescens= Osgood _Proechimys cayennensis arescens_ Osgood, 12 July 1944, Zool. Ser. Field Mus. Nat. Hist., 29(13): 198. _Type locality._--Fazenda Inhuma, below Santa Filomena, upper Rio Parnaiba, _Vitoria do Alto Parnaiba_, Maranhão, Brazil. _Type_: Chicago Natural History Museum, no. 26441, adult male; collected on 5 August, 1925, by Heinrich E. Snethlage. _Range._--Region including the valleys of the Turí-assú and Parnaiba rivers, Maranhão, Brazil. _Diagnosis._--Aristiforms moderately wide and not conspicuously stiff; general color of upper parts near (15'a) Ochraceous-Orange; incisive foramen long and wide; vomerine sheath complete or incomplete; upper molariform teeth and lower premolar with three counterfolds; lower molars with only two. _Pelage._--_Aristiforms on middorsal region_: Whitish basally, gradually blackening toward tip; total length, 19 to 21 mm; maximum width, 0.7 mm. _Setiforms on middorsal region_: Whitish basally or on basal half, gradually becoming gray and then blackish toward tip, but interrupted by long (5 to 6 mm) subapical zone near (15'_a_) Ochraceous-Orange; total length, 15 to 16 mm; maximum width 0.05 mm. _Setiforms on outer thighs_: Whitish on basal half, gradually becoming gray and then blackish toward tip but interrupted by Ochraceous-Buff, subapical zone; tip sometimes not conspicuously darker than subapical zone; total length 18 to 25 mm; maximum width, 0.03 mm.