p.1

Modiolopsis? primigenius, Conrad, Hall, Pal. of N.Y. vol. 2 p. [11 pl. 2] Cypericardia alata, Hall,; N.Y. Geol. Rep. p. 48 fig. 3.

Subrhomboidal, rounded anteriorly, expanded and alate posteriorly; hinge-line straight, longer than the length of the shell; anterior extremity short; ventral margin rounded; surface marked by strong concentric imbricating lines, which are crossed by fine radiating striae on the posterior half of the shell.