1'J4 K('/c Species of Fossils fniiii Ohia. 



field, Ohio ; associated with Meristella bella, ytideospira roiuii- 

 data and Leper (lit i a alta, oceiiiTiiig sometimes in great inim hers, 

 almost covering the surfaces of shdjs. 



]Vucleo»pira rotundata, n. ^^. 



Pal. O., Ill, Plate I, Figs. 11-14. 



yiiell atlaiuiug a rather large size for the genus, being often more than 

 half an inch in transverse diameter, and when of medium or large size, 

 strongly ventricose or rotund. The younger individuals, however, are de- 

 pressed-convex or lenticular in profile. Length of the shell as great or 

 greater than the transverse diameter. Beaks small and incurved, not at all 

 conspicuous. Valves marked by a slight depression along the median line, 

 strongest on the ventral side. 



This species, like all those of this formation yet ohtained in 

 Ohio, are mostly internal casts and impressions ; consequently 

 the true features of the shell are not readily obtained. The 

 general features of the species, however, are preserved suffi- 

 ciently for identification and comparison, when good individuals 

 are selected. The shell hears much resemblance to N. ventrieusa. 

 Con., from the Lower Helderberg group of New York, in its 

 general form, except the much greater size and more elongated 

 form of the adult individuals. There is more difficulty in sepa- 

 rating them satisfactorily from the casts of Meristella hella. 

 Hall, with which they are associated. In fact, it is all but im- 

 possible to do this with certainty, unless they are in a good state 

 of preservation, as the difference in the form of the muscular 

 imprint of the ventral valve, and the more strongly incurved 

 beaks, are the only features that can be relied upon. 



Formation and Locality. — In the hydraulic limestone of the 

 Lower He'derberg grouj), at Greenfield, Ohio. 



Rhync'honella liydraulica, n. sp. 



Pal. O., Ill, Plate 1, Fig. 17. 



Shell rather smaller than medium size, transversely oval in outline and 

 ventricose in profile ; the dorsal valve being highly convex, and the ventral 

 somewhat depressed convex. Beaks small, not prominent or conspicuous ; 

 that of the ventral valve moderately incurved, and the other rather strongly 

 incurved. Surface of the shell marked by from sixteen to eighteen simple 

 plications, four of which are strongly elevated on the front half of the dorsal 

 valve to form the mesial elevation, which does not extend beyond the mid- 



