THE EURYPTERIDA OF NEW YORK II 
These sandy shales are full of organic remains, partly of the supposed 
seaweed Sphenothallus latifolium 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 Clima- 
cograptus typicalis and Triarthrus becki. 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 assem- 
blage, 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 de- 
posited off a northeast-southwest coast line in an area of maximum de- 
position, 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 colo- 
nies mentioned. 
JoHn M. CLARKE 
