Page:The Eurypterida of New York Volume 1.pdf/13

 These sandy shales are full of organic remains, partly of the supposed seaweed  Hall and partly of what appear to be large undefined patches of eurypterid integument. In the black shales the eurypterid remains are rarer but their surface sculpture is excellently retained, and here their organic associates are  and. As a result of imperfect retention of these eurypterids in the rocks where they most abound and their sparseness in the shales which have best preserved them, we are still left in ignorance of the full composition of this assemblage, but it is safe to say genera, species and individuals were abundant at this early period, and the evolution of distinctive characters which we have heretofore recognized only in a later period had progressed to so sharp a differentiation, that we are compelled to carry back further in history, some of the commoner generic designations. These remains in the Frankfort shale are distributed through fully 1500 feet of strata deposited off a northeast-southwest coast line in an area of maximum deposition, and it is difficult to conceive that the physical conditions of the habitat of these merostomes were those of an inshore pool—rather those of a purely marine basin where sedimentation went on rapidly in an appalachian depression. Hence this occurrence is without parallel among our assemblages of these creatures in respect to long endurance.

All other occurrences of Siluric eurypterids in New York have been desultory and indicate no intercommunication between the pools or colonies mentioned.