84 NEW YORK STATE MUSEUM 
species. The presence here of heavy beds of conglomerate with very 
thin shale seams between corroborates the view that these forms were but 
little adapted to digging in the mud. The prevalence of Stylonurus 
in the fauna would seem to support Laurie’s suggestion that Stylonurus 
possessed purely littoral habits. 
The sedimentary facies in which the Otisville and Schenectady faunas 
are involved is not a usual accompaniment of the eurypterids, as fine 
mud rocks constitute the prevailing sediment and relatively broad-headed 
forms the expression of the body. 
If one tries to picture the group as a whole, the typical habit would 
appear to be that of the mud grubber, and the broad carapace, relatively | 
broad preabdomen, the flippers. and the tail spine will be the most import- 
ant elements in producing this picture. 
It is very interesting to note 1n this connection that a subclass of an 
entirely different phylum, viz, the Ostracophora (Cephalaspis, Pteraspis [Old 
Red Sandstone of Scotland]), among the fishes, lived at the same time with 
the eurypterids, is frequently associated with them in the rocks, had 
acquired the same mud groveling habit and a similar general form. The 
theory that these earliest fishlike vertebrates are derived from the arthro- 
pod stem, and have features in common with the merostomes (euryp- 
terids) and arachnids (scorpions etc.) is still seriously defended by some 
competent investigators. Eastman, in an excellent essay' on the evolu- 
tionary history of the fishes, has emphasized the fact that the merostomes 
and arachnids at this early date had already diverged too widely along 
certain directions from the primal trilobitic type of organism, to be the 
possible ancestors of backboned animals, and such resemblances as are 
shared by merostomes and early fishlike vertebrates are explained as 
‘‘due to mimicry, or to adaptation of creatures of different grades to a 
similar environment.”’ | 
We are here not so much interested in the problem of the possible 
derivation of the vertebrates from the merostomes, as in the fact of the 
1C. R. Eastman. Iowa. Geol. Sur. Rep’t 1908. 18:5r1f. 
