Page:The Habitat of the Eurypterida.djvu/242

234 Further corroboration is offered by Van Ingen's discovery in Oneida county already referred to. In the concretionary block obtained from that locality and determined from lingulas and orbiculoideas in it to come from dark gray shales with intercalated waterlimes and dolomite beds 21 feet below the base of the red Vernon shale, were found three carapaces and fragments of a eurypterid, which Clarke and Ruedemann have named Eusarcus vaningeni. They state that "the outline of the body . . . . the visual surface . . . . the appendages, so far as seen, are like those of E. scorpionis. The tergites and sternites have the form and relative dimensions of E. scorpionis. . . . . The ornamentation is that of E. scorpionis, but the scales are smaller and more clearly arranged" (39, 420, 421). It is also somewhat related to E. cicerops from the Shawangunk, but the relation is generic rather than specific. That this species of Eusarcus, more closely related to a species in the Bertie than to a contemporary species in the Pittsford, should be found in the waterlime facies of the Pittsford rocks in a region but a few miles distant from the mouth of the subsequent Herkimer river, is a most unusual corroboration of our theory. It is exactly what could have been prophesied. How such an occurrence is to be explained on the lagoon theory is puzzling.

If the river hypothesis is the correct one it must account for the migration of the eurypterids from the Buffalo region to the Baltic during the Salinan or early Monroan. If we assume the existence of two rivers flowing from the rather low and flat limestone-covered country to the north, into a sea which had its shore extending through New York, as indicated on the map (fig. 8), it would not be difficult to understand that the shed exoskeletons of arthropods inhabiting the waters of these rivers and occasionally dead or even living individuals would be carried down stream, and become embedded in the fine lime sediment of the two neighboring deltas or in the interstream areas. Probably the eurypterids themselves were seldom carried down to the debouchures, since it is their molted exoskeletons which are generally found. To account for the similarity of the Buffalo and Herkimer faunules, it is necessary to postulate the interfingering of the headwaters of the Bertie and Herkimer rivers. The physical and faunal conditions would then be analogous to those existing at the present time in the Columbia and Missouri rivers, as outlined on