Based on approximately 25,000 specimens from the Miocene and Pliocene of the Cibao Valley, northern Dominican Republic, the bivalve family Propeamussiidae is represented by two genera and four species, including two new species. The family Pectinidae is represented by three subfamilies, six tribes, 18 genera, and 35 species, including six new genera, 15 new species, and one new subspecies. Assemblages of these families change composition going upward in stratigraphic sections measured along each major river, reflecting increasing depth of deposition, changing bottom conditions, and association with coral reefs or marine grasses/algae.