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Published online by Cambridge University Press: 14 July 2015
Echinus gyracanthus Eaton, 1832, was the first tentaculitid reported from North America, but the original description and illustration are vague by present-day standards. Study of the type material and topotypes from the Lower Devonian Manlius Limestone in the Town of Schoharie, New York, suggests that Tentaculites gyracanthus (Eaton) is a discrete species, but one with pronounced and remarkable intraspecific variability. Tentaculites simmondsi new species also occurs in the same unit and locality.