298 PALEONTOLOGY OF NEW YORK. 



Valves moderately convex below the umbonal ridge, sometimes more con- 

 vex ; depressed convex or nearly flat above the umbonal slope. 



Beaks sub-anterior, small, closely incurved. Umbo prominent. The 

 umbonal ridge is more or less strongly defined, extending in a slightly curv- 

 ing line to the post-basal extremity. 



Test strong, marked by somewhat irregularly rugose or undulating lamel- 

 lose striae, which make an abrupt curvature or an angular return in crossing 

 the umbonal ridge. Interior unknown. 



Three specimens have the following respective dimensions: Length 60, 51, 

 and 32 mm. ; height 35, 29 and 18 mm. 



This species is distinguished by its short form, rounded posterior extremity, 

 and rugose surface characters. 



Formation and localities. In the shales of the Hamilton group, shores of Canan- 

 daigua, Cayuga and Seneca lakes, and near Schoharie, N. Y. 



GONIOPHORA TRUNCATA. 

 PLATE XLU, FIGS. 9, 10 ; AND PLATE XLIV, FIGS. 1-5. 

 Ooniophora truncata. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 44, figs. 1-5. 1883. 



Shell of medium size, trapezoidal ; length more than twice the height ; basal 

 margin rounded in the anterior part, slightly sinuate a little anterior to the 

 middle and nearly straight or slightly curving to the post-basal extremity ; 

 posterior margin obliquely sub-truncate, slightly curving. Cardinal line short, 

 straight. Anterior end short, rounded, limited by an oblique sinus extending 

 from the beak. 



Valves convex below the umbonal ridge, gibbous in the umbonal region ; 

 the area above the umbonal ridge is flat or concave, or sometimes a little 

 convex. 



Beaks anterior, acute and incurved ; umbo prominent, angular. Umbonal 

 ridge strongly defined, acutely angular, extending to the post-basal extremity. 



Test of moderate thickness ; entire shell marked by fine, lamellose, con- 

 centric striae, and that portion of the surface between the xmibonal ridge and 



