68 PALEONTOLOGY OF OHIO. 



slopes rapidly to the obtusely rounded beak; basal or front margin 

 broadly rounded. Beak of the ventral valve projecting a little beyond 

 that of the dorsal ; the edges of the cardinal border strongly and abruptly 

 inflected, forming an area along the entire cardinal portion of the valve, 

 and leaving the outer margin of this portion of the valve saliently angu- 

 lar. Under the beak, and extending across the area to the beak of the 

 dorsal valve, there is a rather small, slightly raised, and moderately con- 

 vex deltidium, which does not appear to have been separable from the 

 other portion of the shell, so far as can be determined from the material 

 in hand. (The precise nature of this deltidial piece is not fully deter- 

 mined.) Border of the dorsal valve also slightly inflected at the apex, 

 and for a short distance below on both sides, but not forming an area as 

 on the ventral valve. 



Surface of the valves convex, the ventral most ventricose ; sometimes 

 marked by scarcely defined angulations, extending from near the apex of 

 the valves to the lateral angles of the basal border. Other specimens 

 have the surface evenly convex, or marked along the center of one or both 

 valves by a broad, shallow depression. Dorsal valve most prominent and 

 ventricose near the beak. 



Surface of the shell marked by fine, closely arranged, irregular, con- 

 centric, depressed lines ; not lamellose, but leaving the spaces between 

 the several lines flat, or slightly rounded. The surface not otherwise 

 marked or sculptured, but smooth and polished. The interior of the 

 valves are each marked by a strong, rounded, longitudinal ridge, extend- 

 ing nearly one-half the length of the valve, and usually situated about 

 half as far from the cardinal extremity as from the basal border. The 

 muscular markings are very large, extending over a large portion of the 

 surface, but on the specimens examined, not quite distinct enough for 

 description. 



This shell has usually been referred to Lingula quadraia, Eichwald, but 

 is in reality a very different and distinct species. The form of Eich- 

 wald's species, judging from the best figures to which we have access, is 

 broadly elliptical, more distinctly rounded at the base, and less angular 

 at the rostral end, with a less pointed beak, and the lateral margins of 

 the shell sub-parallel. Almost the same differences are noticed when 

 compared with the New York shells referred to that species, they having 

 nearly or quite the characters of the European shell. 



There may be some doubt as to the proper reference of the species to 

 Salter's genus Lingulella. The presence of the narrow cardinal area, 

 although not exactly of the nature of that of Lingulella, precludes the pos- 



