Proechimys decumanus (Thomas, 1899) . Ann. Mag. Nat. Hist., ser. 7, 4:282.

TYPE LOCALITY: Ecuador, Prov. de Guayas, Changón .

DISTRIBUTION: NW Peru, SW Ecuador, Pacific lowlands.

COMMENTS: Subgenus Proechimys . Listed as a subspecies of cayennensis (= guyannensis) by Cabrera (1961:520), but as a species by Corbet and Hill (1991:205), Nowak (1991:943) and Emmons and Feer (1990).