Page:The Eurypterida of New York Volume 1.pdf/267

 The question of the phylogenetic relation of Dolichopterus to Stylonurus, Drepanopterus and Eurypterus has been fully dealt with in the introductory chapter to which we here refer.

Besides the three species of Dolichopterus from the New York rocks thus far mentioned, the Bertie waterlime at Litchfield and the Shawangunk grit at Otisville have each furnished a type represented only by the carapace;  and  ; and the Frankfort shale has afforded the fragmentary remains designated   and.

From the waterlime beds of Litchfield we have a swimming leg, which possesses in general the characters of Dolichopterus but has a greatly differing palette or terminal segment. The latter is elongate oval and strikingly resembles the palette of Pterygotus. As the palette in Pterygotus is the eighth segment, while that of Dolichopterus is the ninth, this similarity can hardly be more than the result of convergence. This limb is as far different from that of the genotype,, in one direction, as that of   is in another. In this the relative compactness and strength of the swimming leg of  is carried to extreme, in the other the tendency of   to the development of broad lobelike appendages.

These few species together indicate a greater variability in the characters of this genus than is shown by other genera.

The genus is at present represented by seven American and two European species, viz: