LAMELLIBRANCHIATA. 459 



This species resembles S. contractus of the Hamilton group, but is a larger 

 shell, and differs in the more direct umbonal ridge, less gibbous valves, and in 

 the absence of a sinuosity in the posterior margin. 



Formation and locality. In the Waverly sandstone, at Granville, Licking 

 .county, 0. 



SCHIZODUS iEQUALIS, n. Sp. 



PLATE LXXV, FIG. 35 ; and PLATE XCV, FIG. 29. 



In part Cytherodon (Sehizodus) qvadrangularls. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : 



PI. 75, figs. 31-36 (35 in error). 1883. 



Shell large, obovate ; body of the shell sub-triangular ; length a little greater 

 than the height ; basal margin regularly curved. Post-inferior extremity 

 very slightly produced. Posterior margin somewhat vertically truncate. 

 Cardinal line short. Anterior end large, contracted beneath the beak and 

 broadly rounded below. 



Valves gently convex below, becoming moderately gibbous in the middle. 



Beaks sub-central, elevated, rising considerably above the hinge-line. 

 Umbonal slope obtusely sub-angular, extending to the post-inferior extrem- 

 ity. Post-cardinal slope rather wide, gently concave. 



Surface marked by fine concentric strias, which are partially preserved on 

 the nearly smooth casts. 



A large specimen has a length of 52 mm. and a height of 45 mm. 



This species bears considerable resemblance to S. Chemungensis, var. quadran- 

 gularis, but the base is more broadly rounded, and the anterior portion is more 

 expanded below, giving the shell a more equilateral appearance. 



Formation and locality. In the Waverly sandstone, at Granville, Licking 

 county, 0. 



