Page:The Eurypterida of New York Volume 1.pdf/196

 Remarks. In aspect,  is greatly different from all its American congeners. This is largely due to the terete form of the body that apparently is without preabdominal expansion. A few specimens [ pl. 22, fig. 8] indicate that there was a slight expansion, but it seems to have found its expression mostly in an increased vertical convexity of the body. This convexity both of the dorsal and ventral sides producing the subcircular section of both preabdomen and postabdomen, is shown by several specimens which are but slightly compressed. A species quite similar to our type in both form of body and size is  Salter from the Downtonian (uppermost Ludlow) of Great Britain. Its carapace, however, seems to have been a little longer

and the eyes a little more forward in position. From the other species of Eurypterus these two forms differ in their long, gradually tapering, terete body and the small size of the swimming legs.

The variability in the size and position of the eyes is commented upon in the preliminary description. Note might also be taken of the confusing variability in the outlines of the carapace. A survey of a great number of carapaces shows that the variability of features which in other species exhibit considerable stability, is for the most part due to the great convexity of the carapace of this species and the resulting various modifications under the influence of differing directions of compression. The accompanying text figures are inserted to illustrate this fact. In figure I the carapace has been vertically and gradually compressed so that the eyes are projected on the horizontal plane directly below their original position. The uninterrupted concentric wrinkles and the normal size of