Page:The Eurypterida of New York Volume 1.pdf/178

 suggestive distinctive character appears to us to be the great difference in the relative sizes of the compound eyes. In  they reach about one third the length of the carapace, but in both   and   they are but one fifth or less of the length of the carapace. For this reason  makes a rather youthful impression when compared with our forms. Altogether, the differences are so small that Schmidt's suggestion that they are but geographical varieties, is fully supported.

The relations of  and   are described under the latter species. It may be here stated that the two are more closely related to each other, than either of them to, indicating that they had but lately separated. Their differences rest mainly in the shape of the carapace and they are duplicated by those between  and , two forms associated in the same (Baltic) rocks.

The  described by Sarle from the Pittsford shale, is also very closely related to   and lacustris, indeed is hardly more than a mutation and therefore undoubtedly a direct ancestor of the two later Bertie waterlime species.

Several of our specimens of  are so favorably preserved that they present features not observed before. The most important of these is that represented in plate 6, figure 6, which comes from a porous bed of coarse dolomite at Morganville, N. Y., in which the integuments are but little or not at all flattened. It shows a distinct glabella, corresponding in form and extension to that of Limulus and obviously due to the same causes. The same specimen also exhibits a deep furrow surrounding the lateral eyes and an obscure broad ridge connecting the latter and bearing the ocelli. The frontal slope is even and uniform and a narrow flat or slightly depressed border is found inside the beveled edge. Another partially compressed specimen [ pl. 6, fig. 5] exhibits the glabella and a broad smooth border, corresponding in extent to the underlying frontal membrane of the underside of the carapace.