150 PALEONTOLOGY OF OHIO. 



forms a broad, shallow depression around the shell at this point. Curva- 

 ture of the shell very moderate throughout the entire length, the arc of the 

 inner side deviating but little from a straight line, while the curvature of 

 the outside is greater by the increased diameter of the shell ; transverse 

 section nearly circular, a very little flattened in the dorso-ventral direc- 

 tion, which may be partly due to compression. Septa numerous, rather 

 closely arranged, measuring about six in the lower part, and over eight 

 in the upper part, in a distance equal to the diameter of the shell at the 

 top of those included in the measurement. Position of the siphuncle 

 not observed. 



Surface of the cast longitudinally fluted, and yet, more distinctly on 

 the fragments, preserving the shell partially exfoliated or eroded. The 

 fl-Utings consist of sharp, elevated ridges, with regularly concave inter- 

 spaces. On the body of the shell the ridges are a little more than a line 

 apart from crest to crest, numbering twenty-seven in the circumference 

 of the shell. 



The species is entirely unlike any other form of -the genus yet 

 described from rocks of this age, in the slight curvature and lirated sur- 

 face, combined with the circular section. 



Formation and locality : In limestones of the Kiagara group, at Yellow Springs, Ohio. 

 Ohio 3tate collection, and collection of Columbia College, New York. 



Crttoceeas Heetzeri (n. sp.). 



Plate 8, figs. 7, 8. 



Shell of medium size, moderately arcuate, and rather rapidly expand- 

 ing to the outer chamber ; broadly ovate transversely, the largest on the 

 outer side of the center, the two diameters being as eleven to thirteen. 

 Outer chamber short, rapidly contracting above, and rounded to the con- 

 strictions of the aperture ; the height being somewhat less than the 

 smallest transverse diameter, the point of greatest elevation being near 

 the dorsal side of the aperture, whence the surface slopes rapidly, but 

 with some convexity, to the inner side of the shell. Aperture deeply 

 lobed, the dorsal portion first forming four lobes, two on each side of the 

 center, the inner ones afterwards becoming again divided, giving three 

 lobes to each side of the median line, with a deep median sinus dividing 

 the two sets on the dorsal margin. The inner or ventral portion of the 

 aperture forms an elongate ovate opening, connected by a narrow slit 

 with the dorsal lobes, and reaching to nearly one-third of the distance 



