134 PALAEONTOLOGY OF OHIO. 



The specimens of this species which have been observed are in the 

 condition of casts of the interior, and, of eourse, the surface features are 

 more or less obscured; but on specimens at all well preserved the fascic- 

 ulate character of the strise is readily recognized, and the mesial fold and 

 sinus very distinct, the margins of the fold beiflg often quite angular. 

 These features, and especially the coarse fasciculate striaj, will serve to 

 distinguish the species from any other shell found associated with it. 



Formation and locality : In the limestones of the Niagara group, at Yellow Springs, 

 Ohio, and also in the Clinton group, at Dayton, Ohio. Collected by Prof. E. Orton. 



Genus EHYISTCHONELLA, Fischer. 

 Rhyxchonella neglecta. * 



Plate 7, fig. 15. 



Atrypa neglecta, Hall; Pal. N. Y., Vol. II., p. 274, pi .57, fig. 1, 1852. 

 Rhynchonella neglecta, Hall; 12th Eept. State Cab., p. 78, 1859. 

 Rhynchonella neglecta; Meek; Pal. Ohio, Vol. I., p. 179, pi. 15, fig. 3. 



Cavities left by the removal of the shells of this species by solution, 

 and showing the impression of the ex'^erior surface and characters, are 

 common in some specimens of limestone examined from the Niagara for- 

 mation at Cedarville, Greene county, Ohio. Casts made with gutta- 

 percha in these cavities furnish the following features, which agree pre- 

 cisely with specimens from the Niagara shales of New York : 



Shell small, seldom measuring three-eighths of an inch in their greatest 

 diameter ; form sub-triangular, or triangularly ovr.te ; broadest in front, 

 with a small, sharp, slightly incurved beak ; distance across the valves 

 from side to side much greater than the dorso- ventral diameter; front of 

 valves rounded. Dorsal valve a little the most convex, somewhat regu- 

 larly arcuate from beak to front ; sides more strongly rounded ; ventral 

 valve having the sides somewhat angular from the abrupt depression of 

 the mesial sinus. 



Surface marked by about twelve sharp, angular plications, of which 

 there are three in the sinus and usually four on the mesial elevation. 

 Surface markings on the plications not preserved, owing to the unfavor- 

 able condition of preservation. 



Formation and locality: In the Niagara group, at Cedarville, Greene county, Ohio. 

 State collection. Collected by Prof. E. Orton. 



* See observations on this species under R. scobina. 



