New records of Macrovalvitrematidae Yamaguti, 1963 are reported from Puerto Rico including Buccamagna archosarga n. gen., n. sp. from the western Atlantic sea bream Archosargus rhomboidalis, Pseudotagia pomadasys n. sp. from the roughneck grunt Pomadasys corvinaeformis, and new locality records for the species Neopterinotrematoides avaginata Suriano, 1975 and Macrovalvitrema argentinensis (Suriano, 1975) n. comb. from the whitemouth croaker Micropogonias furnieri. Buccamagna n. gen. is based on the anterior end and the oral disc being much larger and wider than width of the body proper, by having a pair of rectangular and sclerotized oral suckers, by lacking a pharynx, by having an excessive narrowness in the proximal area of both valves, and by having both valves of the 3 pairs of large clamps armed with several accessory sclerites. Pseudotagia pomadasys n. sp. is distinguished by the absence of serration of lateral sclerites and the relative size of the clamps, having the 2 larger pairs positioned centrally in the haptor and the 2 smaller pairs in the outer positions. Macrovalvitrematoides and Neomacrovalvitrema are synonymized with Macrovalvitrema, which is amended to include Macrovalvitrema micropogoni (Pearse, 1949) n. comb. and Macrovalvitrema argentinensis (Suriano, 1975) n. comb. based on recognition of identical clamp morphologies. In this study the clamp is emphasized as the key taxonomic character for macrovalvitrematid genera. Except for Pseudotagia, the Macrovalvitrematidae have distinctively longer than wide clamps (at least twice as long as wide); with the dorsal valve larger and with a more-complex skeletal structure (g1, g2, i, k, and f sclerites) than ventral valve (c and d sclerites); and 2 clamp morphologies. Characteristics not previously described but present in all macrovalvitrematid monogeneans except Pseudotagia included: (1) asymmetrical plate (plate b) along the ventral valve with a thin fissure on one side, and (2) mirror image arrangement of the pairs of clamps.