506 Systematic Paleontology 



beyond which is a subaiigular ridge. Between this ridge and the slightly 

 thickened cheek margin the surface is concave. The entire lateral and 

 anterior margin of the head is ornamented with a continuous series of 

 from twenty-five to thirty-five triangular, tooth-like processes, largest in 

 front and decreasing regularly in size to the genal angles. The surface 

 of the glabella and those portions of the cheeks lying between the eyes and 

 the glabella, except in the furrows, is covered with rather coarse, irregu- 

 larly arranged, circular tubercles, the outer portions of the cheeks, includ- 

 ing the marginal denticles, being finely papillose. Thorax consisting of 

 eleven segments, the axis a little less than one-third the entire width, 

 pleurte extended into sharp, posteriorly pointing spines. Pygidium sub- 

 triangular in outline, the posterior extremity produced into a dorsally 

 curving, attenuate spine, a little less than one-fourth the total pygidial 

 length. Axis depressed convex, indistinctly subangular along its median 

 line, about one-fourth the entire width of the pygidium at its anterior 

 margin, its sides nearly straight, gradually converging to the obtusely 

 rounded posterior extremity, which lies a little anterior to the base of the 

 posterior pygidial spine. Pleurae with no conspicuous marginal border, 

 flattened above, becoming rather strongly convex in the middle, and then 

 sloping away to the lateral margins with a slightly convex surface. Axial 

 segments fifteen in number ; pleural segments grooved, eleven in number, 

 curving rather abruptly backward as they approach the margin, the two 

 or three posterior ones nearly straight. Each segment of the pygidium 

 marked by a more or less irregular line of tubercles." Weller, 1903. 



The pygidium figured has a striking resemblance to published figures 

 and descriptions of this species in the duplicate ribs and in the tubercles 

 on the axial lobe. But except for the width of the axis, it might with equal 

 propriety be referred to D. bisignatus Clarke. It is too imperfect for 

 accurate determination. 



Occurrence. — Oriskany Formation, Eidgely Member. Evick Gap, 

 opposite Franklin, Pendleton County, West Virginia. 



Collection. — U. S. National Museum. 



[Ohern.] 



