94 PALEONTOLOGY OF NEW YORK. 



The latter species lias the same number of annulations on both axis and pleura?, 

 and the same general outline; its axis however is more slender, the axial annu- 

 lations transverse and the border less conspicuous and more flattened. 



Distribution. Upper Helderberg group. In the Schoharie grit, at Schoharie, 

 Schoharie county. 



Proktus, sp. ? 



PLATE XXn, FIGS. 5, R. 



\ ingle imperfect cephalon, and two pygidia from the Schoharie grit, differ- 

 ing from those of any species previously described from this horizon, indicate 

 the existence of at least one additional species of Proitus. 



The Cephalon is semi-elliptical in outline, the glabella ovoid and ver}' convex, 

 its anterior extremity tangent upon the frontal border, and the surface without 

 apparent traces of transverse furrows. The frontal border is very broad and 

 sloping; eves relatively small, orbital ridge unusually conspicuous, beneath 

 which the surface of the cheek is grooved, somewhat flattened and thence 

 abruptly deflected to the marginal sulcus ; its extremities were evidently pro- 

 duced into short spines. The occipital furrow is narrow and sharp; the occipital 

 ring broadly rounded. The specimen measures 12 mm. in length and 28 mm. 

 in width. 



The Pygidia exist in the form of casts, and there is no evidence that they 

 belong to the species represented by the cephalon. They are much shorter 

 than in P. angustifrons or P. Conradi, show but six annulations upon the axis 

 and three or four upon the pleuras. 



Distribution. Upper Helderberg group. Schoharie grit: The cephalon is 

 from Schoharie, Schoharie county; the pygidia from the towns of Knox and 

 Clarksville, Albany county. 



Proetus curvimarginatus, n. sp. 



PLATE XXII, FIGS. 13-19. 



General Form and Proportions. Body ovate or sub-elliptical. 



Surface sub-equally trilobate, convex along the axial line, strongly deflected 

 at the margins. Length to width as 2 to 1. 



