Xctc Species nf Fossils from Ohio. 2()'.t 



llelderberg group, ;it Smith tind Price's (juarries, near Colum- 

 bus, Ohio. Collected by Mr. Hyatt. 



CjTloccras orelaceuin, n. sp. 



Pal. O., Vol. Ill, Plate 4, Figs. 2 and 8. 

 Shell of medium size, .somewhat moderately expanding in its upward 

 growth tci the base of the outer chamber, from wliich jjoint it again contracts 

 to the aperture ; the increase not always regular, but in some individuals 

 more abruptly expanding above than below. Sliell slightly curving through- 

 out its length, appearing less arcuate in the upper portion, owing to the 

 contraction of the outer chamber toward the aperture. Transverse section 

 oval, widest in a lateral direction, and with the inner surface much less arcu- 

 ate than the outer or dorsal surface. Outer chamber proportionally short, 

 the length not exceeding the dorso-ventral diameter of the lower end ; mar- 

 gin simple, so far as can be determined from any of the specimens, showing- 

 only a broad, shallow sinuositj^ on each side. Septa somewhat closely 

 arranged and deeply concave, but slightly increasing in distance in the upper 

 part, the average length of the chambers being about one-tenth of an inch, 

 but somewhat more crowded just below the outer one. Siphuncle of mode- 

 rate size, situated a little within the dorsal surface, and very slightly ex- 

 panded within the chambers. Surface of the shell marked only by transverse 

 lines of growth parallel to the margin of the aperture. 



The shells are moderately abundant, and show slight varia- 

 tions in form among individuals, especially in the rate of in- 

 crease in dimensions or in the regularity of the expansion, as 

 well as in the comparative distance between the sei)ta ; a single 

 individual showing a much greater distance between them in the 

 upper part of its length. 'J'he shell would probably be con- 

 sidered by some as belonging to the genus 0)icoceras, as the 

 decrease in diameter in the u})per part of the outer chamber 

 gives to the shell, below, the peculiar bulging appearance supposed 

 to be characteristic of that genus ; but the transverse form and 

 elliptical section, together with the form of the siphuncle and 

 other features, present chai'acters common to the genus Cyrto- 

 ceras. It is most nearly related, in general form, to C. Conradi, 

 Hall, from the Marcellus Shales of New York, but attains a 

 much greater size, has a shorter oiiter chamber, and is destitute 

 of the small lip-like sinus on the ventral side, as seen in that one. 

 The upper portion of Gom^jlioceras oviforme, Hall, from the 

 limestone of the Marcellus Shale, bears considerable resemblance, 

 except in the closing of the aperture, which constitutes a generic 

 dilference. 



