Page:Eurypterids of the Devonian Holland Quarry Shale of Ohio.djvu/13

 cheliceral teeth, and in a considerably different arrangement of these teeth. From the New York Devonian P. (Pterygotus) elleri Ruedemann and the Montana Devonian P. (Pterygotus) montanensis Ruedemann, the stout, short teeth of P. (Pterygotus) carmani are sufficient to distinguish the Ohio form.

The species has been named in honor of Dr. J. Ernest Carman, Ohio State University, who discovered the fish-eurypterid fauna of the Holland Quarry shale.

The holotype (PE5105) and paratypes (PE5106–PE5112, PE5118 and PE5119) are in the collections of Chicago Natural History Museum.

The species is based on a single well-preserved, complete, free ramus of the chelicera. Inward bowing at the distal end indicates that it is the free ramus of the left chelicera. The specimen is broken through the midsection into two parts. Figure 43 is a composite of both parts (✕ 4).

The ramus is a short, stout structure tapering into a curved distal end. The inner margin, armed with teeth, is inclined with respect to the almost straight outer margin, resulting in an overall tapering form. The teeth are short and stout, in keeping with the overall robust aspect of the stem. These teeth are mostly of fairly uniform size, mainly lanceolate to rhomboidal, but some are truncated, giving a nearly quadrate appearance. The two distal teeth are badly worn but apparently were the largest. Wear is also apparent on the succeeding three teeth. No longitudinal ridges ("striations") occur on any of the teeth. The distal end is slightly curved inward; that is, in normal position the end would be curved inward toward the oral opening. The free ramus is estimated to have been 27.5 mm. long on the base and is 5 mm. wide at midsection.

Remarks.—The subgenus Pterygotus (Erettopterus) is poorly represented in North America but is well known in Scotland, England, and Saaremaa (Oesel). The form above described is the first record of the subgenus in the Devonian of North America. P. (Erettopterus) serratus differs greatly from the common P. (Erettopterus) bilobus (Salter) of the upper Silurian of Scotland in having the chela much thicker and in having short, stout teeth in contrast to the slender, curved teeth of the latter. From P. (Erettopterus) osiliensis Schmidt, the