_Mus cinnamoneus_ Lichtenstein, 1830, Darstellung neuer oder wenig bekannter Säugethiere, Berlin, Heft 7, pl. 36. _Echimys myosuros_ Is. Geoffroy Saint-Hilaire, 1838, Comptes Rendus Acad. Sci., 6(26):886, and 1840, Mag. Zool., Paris (ser. 2, année 2):15, 33, 53; Allen, 1899, Bull. Amer. Mus. Nat. Hist., 12(20):261. _Echinomys leptosoma_ Wagner, 1843, Schreber's Säugethiere, suppl., 3:341. _Echinomys myosuros_ Burmeister, 1854, Syst. ubersicht Thiere Brasiliens, p. 199. _Proechimys setosus_ Thomas, 1921, Ann. Mag. Nat. Hist., 8 (ser. 9):141. _Proechimys myosuros_ 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. _Proechimys leptosoma_ 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. _General characters._--Aristiforms wide (1''') and numerous on dorsal parts of body; tail longer (9'') than head and body (8''); hind feet short (1''6'''). _Color_ (According to Lichtenstein and Brants' descriptions).--Black between ears; dark brown on middorsal line with reddish tinge on front and upper side of neck; posteriorly from shoulders there is a greasy shine added to color; this dark, dorsal band widens posteriorly, there encroaching on sides of body; sides lighter brown, sparsely marked with dark brown lines, from sides of head caudad to, and including, outer surfaces of hind legs; outer sides of forelegs colored like outer sides of hind legs; ankles ringed with brown. Tail blackish above, whitish below. Upper surfaces of hands and feet white. _Skull._--No description of skull or teeth found.