Page:Eurypterids of the Devonian Holland Quarry Shale of Ohio.djvu/23

 of each tergite, however, is a single fringe of large, crescentic, flat scales. One of the tergites measures 10.5 mm. in incomplete length.

Remarks.—This species differs greatly from all other associated forms, and can easily be distinguished from them by the distinctive ornamentation, which enables identification from small fragments. The very wide prosoma, having a length-width ratio of 5.2:10, is unusual for the Stylonuridae but recalls forms such as Erieopterus latus (Ruedemann), E. pustulosus (Hall), and E. brewsteri Woodward, of the family Eurypteridae. The diagnostic crescentic eye is, however, a structure not present in any of these. Comparison with other forms is superfluous on a species basis as the distinctive characteristics described above will separate this form from all other eurypterids.

The holotype (PE5120 a and b) and paratypes (PE5121, PE5122 and PE5123) are in the collections of Chicago Natural History Museum.

The lens of dark bituminous Holland Quarry shale in Lucas County, Ohio, was discovered by Dr. J. Ernest Carman of Ohio State University, who kindly donated his collections to Chicago Natural History Museum. I wish to thank Dr. Robert H. Denison and Dr. Eugene S. Richardson, Jr., for the opportunity of studying the eurypterids.