54 FIFTEENTH EEPORT ON THE CABINET OF NAT. HISTORY. 



Geological formation and locality. In shales of the Hamilton group : 

 at Seneca and Cayuga lakes ; at Eighteen-mile creek, and more commonly 

 in the shales east of Cayuga lake, at Delphi and other places. 



GENUS EUOMPHALUS (Sowerby). 



EUOMPHALUS CLYMENIOIDES ( n. s.). ^ Y) ' ^ 

 Shell discoid. Spire depressed below the plane of the outer volu- 

 tions :' volutions about four or five, lying nearly in the same 

 plane, slender and very gradually expanding, rounded above and 

 below, the lower side the most convex, the section transversely 

 ovate, narrower on the ventral or inner side of the volutions, 

 the vertical and transverse diameters about as twelve to thirteen. 

 Aperture transverse, subovate. Surface unknown. Diameter of 

 shell, in the largest specimens seen, one inch and a half. 



This species is known to me in the condition of casts only ; but its form 

 and proportions furnish marked characters. The casts sometimes show im- 

 pressions of transverse strise, which are at intervals apparently crowded in 

 fascicles. The spire is more depressed than in £. planodisciis of the Goniatite 

 limestone, while in that the section of the volutions is nearly circular. 



Geological formation and locality. In the Schoharie grit : Schoharie. 



EUOMPHALUS LAXUS ( n. s.). ^ p ^ y ' / " 2^ 

 Shell discoid. Volutions about four, nearly in the same plane, 

 disjoined throughout their entire extent, very gradually and 

 regularly expanding from the apex : section circular. Aperture 

 (as far as known) subcircular, scarcely expanded. 

 Surface marked by crowded transverse striae, which are sometimes 

 regular and equal, and, on some parts of the shell, more closely 

 arranged, and all directed a little forwards from the inner side 

 of the volution. 



The greatest diameter of the largest specimen seen is one inch 

 and five-eighths, and the diameter of the volution at the aperture 

 is half an inch. 



This species differs from any other in this series of strata, in the distinct 

 separation of the volutions throughout their entire length. The impressions 

 in stone are strongly marked by the transverse striae, and the casts preserve 

 fainter impressions of the same markings. 



Geological formation and locality. In the Corniferous limestone at 

 Schoharie, and in the Hamilton group at Eighteen-mile creek and Alden in 

 Erie county, and in the same formation in Otsego county, N.Y. 



[ September, 



