530 CRETACEOUS PALEONTOLOGY. 



Genus CYMELLA Meek. 



Cymella bella Conrad. 

 Plate LVIIL, Figs. 10-12. 



1875. Cymella bella Con.., Kerr's Geol. N. Car., App., p. 10, pi. 



2, fig. 9. 



1876. Cymella bella Meek, Rep. Inv. Cret. and Tert. Foss. Up. 



Mo., p. 228, text figs. 25-30. 



1877. Leiopistha (Cymella} meeki Whitf., Prelim. Rep. Pal. 



Black Hills, p. 35. 

 1880. Leiopistha (Cymella} meeki Whitf., Rep. Geol. and Res. 



Black Hills of Dak., p. 418, pi. n, figs. 27-28. 

 1886. Cymella meeki Whitf., Pal. N. J., vol. i (Monog. U. S. 



G. S., vol. 9), p. 142, pi. 20, figs. 6-7. 



Description. "Shell of moderate size, transversely oval or 

 ovate, about once and a half as long as high. Valves strongly 

 convex, with large, somewhat prominent beaks, situated much 

 nearer the anterior end. Shell nearly erect, and a little wider 

 at the anterior end than behind. Extremities of the valves nearly 

 equally rounded and the base regularly curved. Cardinal line 

 long behind the beaks, and the margin inflected forming a nar- 

 row, linear, escutcheon-like area. Surface of the shell marked 

 by strong and regularly rounded and regularly increasing un- 

 dulations parallel to the border of the valves. These are crossed 

 by distant radiating ribs, which are strong and vertical in the mid- 

 dle of the valve or opposite the beaks, and become gradually 

 fainter and finer toward the posterior end, apparently becoming 

 obsolete just below the cardinal border, and also before reaching 

 the anterior cardinal margin. These radiating ribs, on the central 

 parts of the shell especially, cut up the surface into rounded nodes 

 by forming depressions across the concentric undulations. Sur- 

 face of the shell and hinge-structure not seen, as the specimens 

 are 'all in the condition of : casts in a fine micaceous marl." 

 (Whitfield.) 



The dimensions of a large left valve are: length, 41 mm.; 

 height, 27.5 mm., convexity, 9.5 mm. 



