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Among the fossils collected on the Yale Scientific Expedition of 1872 are fragments of the skull and dentition of a large pycnodont fish. These were found by O. C. Marsh in the Cretaceous chalk exposures along the Smoky Hill River in Kansas on November 6, 1872. They are of particular interest as an example of extreme reduction of the dentition in an aberrant member of this family of durophagous fishes, and also because of their unusually large size. The specimens confirm the distinctness of a genus described by Leidy from the Cretaceous of Mississippi. It is quite fitting that the species should be named for their discoverer.