634 GEOLOGY OF OHIO. 



Formation and locality : Uoraine shales, Loraine, New York; also 

 in the equivalent middle beds of the Cincinnati group, at Covington, 

 Kentucky, and Cincinnati, Ohio. 



Byssonychia suberecta, n. sp. 



Plate 45, Figs. 13-15. 



Shell exceeding the medium size for the genus, moderate!}* convex, 

 suberect, the length and height as five is to six. Hinge line forming an 

 angle of about 105° with the anterior margin ; this is a few degrees 

 wider than the posterior angle. Anterior outline gently sinuate in the 

 upper half, and in the central part bending forward enough to give the 

 shell the appearance of leaning backward rather than forward ; posterior 

 margin broadly convex; basal half with a semicircular curve. Beaks 

 full, rounded, not very prominent, bending somewhat forward and 

 strongly incurved. Greatest convexity in the umbonal region, but tak- 

 ing the surface as a whole it is more uniformly rounded than in any 

 other species of the genus. Radiating costse rather small, fifty-five to 

 fifty-eight on each valve. Ligamental area about 3 mm. wide, almost 

 vertical, so that in a dorsal view it appears as very narrow, with five or 

 six distinct longitudinal striae. Cardinal teeth apparently three in each 

 valve. Strong posterior lateral teeth are present, but whether more than 

 one in each valve could not be learned from the material at hand. Bys- 

 sal opening long though very narrow. Muscular and pallial impression 

 as usual for the genus. In casts of the interior the beaks are compara- 

 tively erect and obtusely pointed. 



This species has an outline that is closely similar to that of B. cul- 

 traia. The two species are also associated in the same strata, but can be 

 distinguished at once by the rounded instead of carinate beaks of B. 

 suberecta. The latter is also a liitle smaller. B. radiata is probably 

 more nearly allied, but has fewer costae and is a much more oblique shell. 



Formation and locality: Upper beds of the Cincinnati group, at 

 Waynesville, Ohio, and Versailles, Indiana. 



Byssonychia acutirostris, n. sp. 



Plate 45, Figs. 8 and 9; Plate 46, Fig. 10. 



Shell moderately convex, 75 mm. or less in height, acuminate-ovate 

 in outline, the transverse diameter or length usually about two-thirds of 

 the height; without the acuminate rostral portion the outline forms a 

 nearby regular oval. Beaks attenuate, small but prominent, not strongly 

 incurved (rather erect in casts of the interior), obtusely pointed. Upper 

 fourth of anterior side slightly flattened and somewhat sinuate in out- 

 line. Hinge line very short. Radiating costae thirty-six to forty on each 



