A large number of previously unrecorded specimens of mailed catfishes of the genus Metaloricaria Isbrücker, 1975 (Loricariinae, tribe Harttiini, subtribe Metaloricariina) is compared with the known specimens from French Guiana and Surinam. This results in the recognition of two subspecies, viz., M. paucidens paucidens Isbrücker, 1975, from the rivers Oyapock and Maroni (French Guiana, Surinam), and M. p. nijsseni (Boeseman, 1976) from the rivers Suriname, Saramacca, Nickerie and Corantijn (Surinam). These subspecies were originally described as two different species, even within two different genera: Metaloricaria paucidens Isbrücker, 1975, and Harttia nijsseni Boeseman, 1976. Morphometric and meristic data, together with illustrations are given of the two subspecies. Diagnostic characters of Metaloricaria are provided, and its position within the Harttiini is indicated.