Page:The Eurypterida of New York Volume 1.pdf/436

 Rooker farm, Pithole City, Venango co., Pa. The outline is quite regularly semicircular; the posterior parts of the lateral margins slightly concave and the postlateral angles slightly produced but not into distinct mucros as in the original figure. The eyes are small (between one fourth and one fifth the length), the nodes prominent. They are separated by a distance about one half the breadth of the carapace. As in other specimens from sandy beds, the glabellalike ridge of the middle of the carapace is well preserved between the eyes and bears a distinct circular ocellar mound just back of the lateral eyes. This species is probably closely allied to.

The chance exposure of the lower side of the cephalothorax in this genus has brought out a structure which none of the material before examined has displayed and an illustration of the details of this structure is here given. In the anterior median position lies a relatively long plate resembling an inverted lyre, which is identical with the object described by Sarle and reproduced elsewhere by ourselves as the supposed "metastoma of Dolichopterus??" It is the epistoma. It is bounded by sharp sutures on the lateral margins and terminates with its bilobate portion in front of the mouth. On its posterior lobes are two sharply outlined circular scars indicating either the attachment of muscles or more probably the bases of the chelicerae. This epistoma is flanked by two semielliptic plates, the antelateral shields, which in their turn are separated by distinct sutures from the marginal shields at the sides. The latter show a clavate widening at their posterior ends. The narrow posterior doublure, which is not connected with the marginal shield, completes the system of marginal plates on the ventral side of the cephalothorax which hold the appendages and membranes in place.