Page:Eurypterids of the Devonian Holland Quarry Shale of Ohio.djvu/5



In contrast to the Silurian, the North American Devonian deposits have not yielded a rich fauna of eurypterids, although the list of known species is continuously growing. The occurrence of eurypterids in the Holland Quarry shale, a lens locally underlying the Sylvania sandstone at the base of the Devonian in Lucas County, Ohio (see Carman, 1960), adds materially to our relatively meager knowledge of Devonian forms in North America.

The eurypterids in this Lower Devonian deposit are preserved as patches of integument up to four inches in diameter, although most patches cover no more than one or two inches. The preservation of these fragments is excellent, and permits study of minute details in structure and ornamentation. The eurypterids are intimately associated with numerous fishes and land plants in a dark gray to black bituminous shale with numerous single grains of coarse, round, frosted quartz sand, and clusters of these sand grains in pockets, along with small light-gray mud pellets (phosphatic?), some sulphur specks, selenite crystals, pyrite and coaly or carbonized streaks which probably represent mineralized plants. The fishes included are pteraspids, cyathaspids and arthrodires (see Denison, 1960). The pterygotids are by far the most common eurypterids present.

It is of interest to note again the intimate association of primitive fishes with eurypterids. In this bed, the pointed teeth of the large pterygotid chelicerae are very worn. The ends are rounded and all traces of the longitudinal ridges are worn off from the distal ends of the teeth.

It might be well to speculate on the prey on which these chelicerae were abraded. Besides the common fishes and eurypterids, no

Library of Congress Catalog Card Number: 61–12397