The ornamentation of the carapace consists of sharply elevated, hollow tubercles, densely arranged and evenly distributed (absent, however, on the eye nodes) and frequently with a stellate form or provided with a few radiating ridges or wrinkles. A fine granulation occupies the interspaces between the tubercles.
Horizon and locality. Frankfort shale (Schenectady facies) in Dettbarn quarry at Schenectady, N. Y.
Remarks. The forward position and form of the eyes suggest that the species may belong to Dolichopterus, but the carapace is markedly shorter than that of other members of the genus.
Besides the carapace a number of patches of integument have been found which still better display the peculiar stellate ornamentation and the finer granules.
Subgenus ONYCHOPTERUS nov.
This subgenus is proposed for Eurypterus kokomoensis to give expression to the phylogenetic importance of the species as indicating the path of development of Dolichopterus, Drepanopterus and Stylonurus from Eurypterus. Its distinctive characters are the large, squarish carapace, the lack of differentiation of the fourth pair of endognathites, the spurlike form of the ninth segment of the swimming legs and the styliform telson.
Eurypterus (Onychopterus) kokomoensis Miller & Gurley
Eurypterus kokomoensis Miller & Gurley. Illinois State Mus. Bul. 10. 1896. p. 90, pl. 5, fig. 1
Description. Body of small size, relatively broad, about three and a half times as long as wide, attaining its greatest width in the region of the fourth tergite, thence tapering gradually to the telson.
The carapace is decidedly squarish in outline, its anterior angles are rounded and it is little wider than long. The anterior margin is slightly convex and emarginate, the lateral margins subparallel and nearly straight.
