Abstract

Plates grew by addition of calcite at their edges, but at different rates along different edges. Growth along one edge was constant, and is used as a datum for comparison of growth along other edges. Growth curves thus derived provide means of comparing ontogenies of different individuals, populations, or taxa. The genus is revised, the type species Orophocrinus stelliformis (Owen and Shumard) redescribed, and O. campanulatus (Hambach) and O. (Codaster) whitei Whitfield (non Hall, part) placed in its synonymy. Codaster whitei Hall is assigned to Hydroblastus. Orophocrinus occurs in Upper Kinderhookian and Lower Osagean series of Illinois, Iowa, Missouri, New Mexico, and Arizona, and in the Tournaisian and Visean of Europe.

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