212 NEW YORK STATE MUSEUM 
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 indi- 
cating 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 endo- 
gnathites, the spurlike form of the ninth segment of the swimming legs 
and the styliform telson. | 
Eurypterus (Onychopterus) kokomoensis Miller & Gurley 
Plate 25, figures 1, 2; plate 26, figure 2 
Eurypterus kokomoensis Miller & Gurley. [Illinois State Mus. Bul. ro. 
1896. p. go, 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 
rotunded and it is little wider than long. The anterior margin is slightly 
convex and emarginate, the lateral margins subparallel and nearly straight. 
