110 PALEONTOLOGY OF OHIO. 



the posterior angles of the cheeks. Glabella elevated, broadly sub- 

 conical, rounded in front, concave behind ; furrows not visible. 



" Eyes comparatively large and prominent, separated from the glabella 

 by a somewhat deep groove; border of the head broad and flattened. 



"Thorax having the axial lobe very prominent, narrower than the 

 lateral lobes ; segments scarcely arching forward in the middle; lateral 

 lobes geniculate, and having the extremities of the pleura directed back- 

 wards and distinctly furrowed to near their outer extremities. 



" Pygidium small, semicircular, regularly rounded behind, and the an- 

 terior margin straight to near the lateral angles, where it is abruptly 

 curved backwards. Axial lobe narrow, not reaching to the posterior 

 border of the shield, marked by five small annulations, with about the 

 same number on the lateral lobes, which are less distinctly marked. 



" Surface smooth, or very finely granulose." 



We know of no American species resembling this one sufficiently near 

 to require any comparison of characters. The Bohemian species P. sculp- 

 tus, Barr., with which it is compared under the original description of 

 the species, is sufiiciently marked by the one less thoracic segment to 

 prevent the possibility of mistake. In the original description above 

 copied, by some oversight the number of segments is not mentioned in 

 the description of the thorax. There are ten thoracic segments, strongly 

 bent in the lateral portions, and terminating in sharp mucronate points 

 directed obliquely backwards from the geniculations. From P. Spurlocki, 

 Meek (Palfeontology of Ohio, Vol. I., p. 161, pi. 14, fig. 12), it differs so 

 strongly that there can certainly be no danger of confounding them. 



Formation and locality : In the shales of the Hudson Eiver group, at Cincinnati, 

 Ohio. 



