A new Emsian species of the Rhenish bivalve Montanaria Spriestersbach, 1909 is described from specimens that were collected in the York River Formation, Gaspé area. It is reported for the first time in America. This endobenthic species, M.honquedoensis n.sp., developed communities in areas of fine sand embayments or in brackish lagoons related to a sedimentation in a deltaic environment. The acidic benthos in which it lived corroded deeply the beak in the mature population. The diffusion of Montanaria towards Gaspé is explained by the restricted dimension of the Emsian Iapetus Ocean, and it coincides with the bivalve migration, from the western Europe to the northeast of North America, from Early to Middle Devonian. The monogenic family of Montanariidae is revised and its taxonomic affiliation is discussed. The dental and ligamental features of Montanaria indicate an intermediate level of organization between primitive actinodontoids and heterodonts. [Journal Translation]

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