Page:The Eurypterida of New York Volume 1.pdf/272

 cordiform." Its length is more than half that of the carapace, its greatest width (in the anterior fourth) one half of its length. It decreases slightly in width posteriorly. Its lateral margins are nearly straight or but slightly concave. Its posterior end is transversely truncate, slightly emarginate in the middle.

The opercular appendage of the female is seen very imperfectly in Hall's type. It is better shown in the specimen in the museum of the Buffalo Society of Natural Sciences [pl. 44]. It is similar to that of Eurypterus, differing mainly in the greater length and less curvature of the paired terminal pieces. The proximal portion has not been distinctly seen. Traces of the pentagonal areas and the inclosed hastate proximal