154 - PALEONTOLOGY OF OHIO. 



prominent tubercle or node. Pleura marked by a broad, deep furrow, 

 rising from the upper edge near the axis and extending more than two- 

 thirds of the length, terminating on the expanded overlapping portion 

 in a narrow, curving line. On the upper part of the lateral lobe the fur- 

 row occupies fully one-half the width of the rib. 



Pygidium sub-triangular in outline, about as long as the length of the 

 glabella, exclusive of the occipital ring ; its length along the centre 

 about equal to each lateral face, measuring from the antero-lateral angle 

 to the posterior extremity, the lateral lobes being much wider than the 

 axial. Axis obconical, longer than wide, obtusely rounded at the ex- 

 tremity, and not reaching to the border of the plate ; marked by six or 

 seven articulations, exclusive of the terminal one. Lateral lobes round- 

 ed or sloped on the anterior border, the surface abruptly declining from 

 the longitudinal furrow to the lateral margins ; border broad and thick- 

 ened, the four or five articulations extending but little more than half 

 way to the edge of the plate, and not showing any evidence of a central 

 depression. Posterior border of the pygidium broadly notched on the 

 lower edge, not showing except in a posterior view. 



As the specimens obtained in Ohio are always in the condition of in- 

 ternal casts, the characters are, of course, somewhat different from those 

 seen w.iere the substance of the crust is preserved. The species has a 

 very wide geographical range, occurring in nearly all localities of the 

 Niagara formation throughout the country, but usually in the condition 

 of casts in the dolomites of the West. It bears considerable resemblance 

 to C. senaria, Conrad, from the lower geological formations, but differs in 

 several minor points. The most noticeable, and one which readily serves 

 to distinguish the two forms, is the much greater projection of the ante- 

 rior rim of the head, and its more strongly upward curvature in that 

 species. 



Formation and locality : In the limestones of the Niagara group, at Cedarville, and 

 more commonly at Eaton and Yellow Springs, Ohio. 



Genus ENCRINURUS. 

 Encrinurus ornatus (n. sp. ). 



Plate 7, fig. 16. 



Cybek punctatus, Hall; Pal. N. Y., Vol. II., p. 297, pi. 66a, fig. 1, 

 Not Calymene punctatus, Dal., Hisinger, and others. *' 



Among the fossils from the formation at Yellow Springs, Ohio, there 

 are several specimens of pygidia of a species of Encrinurus, one of 



