Page:The Eurypterida of New York Volume 1.pdf/117

 The succession of habitats is hence, according to our evidence, the reverse of that suggested by Chamberlin's hypothesis noted at the beginning of this discussion.

The cause of the withdrawal from the sea of these well armed and often gigantic eurypterids into the brackish and fresh water is a problem of much interest. Perhaps the development of the more agile and more advanced fishes put these slow and archaic merostomes on the defensive and finally forced them altogether out of the sea. Their association with clumsy and heavily armed, equally archaic Old Red fishes which clearly suffered a like fate from their own more advanced relatives, would seem to be very suggestive in this connection.

It may be mentioned that even the gigantism of these arachnids, as typified by, is probably an indication of race degeneracy, as gigantism is generally, and as such is also suggestive of their increasing failure to cope with the conditions of marine life.

The collections from the shale beds of the Shawangunk grit at Otisville have furnished an unrivaled series of larval stages of one species each of the genera Eurypterus, Pterygotus, Stylonurus and Hughmilleria. Many of the growth stages measure but 2 millimeters or even less in length and hence so little surpass in size the eggs of Limulus and probably