Page:The Eurypterida of New York Volume 1.pdf/197

 the eyes characterize this frequent mode of preservation. In figure II the vertical pressure has acted with a slight centrifugal component, the eyes have wandered outward and become long, narrow and slitlike while the wrinkles are only found parallel to the lateral margins. In the specimen figure III the reverse has taken place; a component acted in a centripetal direction and moved the eyes inward. In this case the latter always appear reduced in size, the whole change producing a strangely different aspect of the head, which is also frequently somewhat squarish in outline [ pl. 22, fig. 1]. In this state of preservation the margin of the head is frequently cut by many radiating marks indicative of the intensive flattening out of the outer portion of the carapace. In figure IV the pressure acted from behind and the head is folded over forward and nearly always shortened. In figure V, the pressure acted obliquely, so that the left eye is completely flattened out and the other reduced to a narrow crescent. The possibility of so many different expressions of form under pressure must be taken into account in construing specific values.

Description. Carapace semicircular (width of type, 45 mm, length, 30 mm), both frontal and lateral margins forming a continuous curve; posterior margin well preserved in the middle portion only, which is rather strongly concave; genal angles not clearly seen; eyes submarginal, of large size, occupying one fourth the length of the lateral margin, situated behind the middle line of the carapace; visual surface crescent-shaped (in compressed condition); eye surrounded on the outside by a distinct dumbbell shaped depression; ocelli well defined, large and lying between the anterior portions of the lateral eyes.

The ornamentation is obscured by the compression of the specimen; patches of the surface exhibit a shagreenlike sculpture which suggests that the better preserved fragments of integument with similar ornamentation, found in the same beds, belong to this species.