Page:Eurypterids of the Devonian Holland Quarry Shale of Ohio.djvu/19



This unusual species is based on the holotype (PE5120) and three paratypes (PE5121, PE5122, PE5123) which together retain all details of the prosoma, the doublure, and fragments of the tergites. It is a pleasure to name this unique species in honor of Dr. Eugene S. Richardson, Jr., Curator of Fossil Invertebrates at Chicago Natural

History Museum, who has contributed considerably to my study of the Eurypterida.

The prosoma is very wide, forming an almost perfect parabola, and is straight along the base. The lateral eyes are small and crescentic, and are covered by a conspicuous palpebral lobe; they are located slightly behind the center of the carapace and closer to each other than to the lateral margins (see figs. 48–50, 52). The ocelli are probably very small, as they were not detected. The ocellar mound, upon which the ocelli would be situated, was, however, preserved, and this occupies a nearly central position on the carapace, midway between and anterior to the center line of the compound eyes. A wide, prominent, flat marginal rim surrounds the carapace, becoming narrower toward the genal angles (see figs. 50, 51).

The ornamentation is highly distinctive and can be recognized even in small fragments in the black shale (see figs. 48, 50, 52). On the prosoma the central and posterior-central parts consist of