GASTEROPODA. 61 



more abrupt convexity on the lower side of the volution, while the species of 

 the Hamilton shales is often, or usually, only moderately convex, and never 

 raised above a circular curve. 



Formations and localities. In the Corniferous limestone at Schoharie, and in 

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

 the same formation in Otsego county, N. Y. 



Euomphalus (Phanerotinus) Eboracensis. 



PLATE XVI, FIGS. 19-23. 



Euomphalus Eboracensis, Hall. Descriptions of New Species of Fossils, etc., p. 27. 1881. 

 " " Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 55. 1862. 



" " " Illustrations of Devonian Fossite: Gasteropoda, pi. IB. 1876. 



Shkll discoid. Volutions subrotund ; the section very obtusely pentahedral ; 

 the upper side a little flattened along a narrow space, regularly curving on 

 the inner side, somewhat flattened or depressed-convex on the lower side ; 

 the dorsum is flattened or truncated, and between this and the summit is 

 a narrow flattened space. The dorsal side, separated by an obtuse angle, 

 is nearly vertical to the plane of the volution ; towards the aperture the 

 inner side becomes straight, and the lower side scarcely flattened. 



Surface marked by closely arranged lamellose striae, which are crowded and 

 fasciculate, giving a somewhat rough exterior on the outer volution, while 

 the tube is constricted at irregular intervals, and the dorsum is marked by 

 cicatrices from the attachment of fragments of shells or other bodies, 

 which have left their impressions after removal or are still found adhering. 



These cicatrices have sometimes great regularity, but they are usually at 

 irregular distances, and the interspaces are sometimes distinctly constricted ; 

 at other times slightly swelling. The general form of this species is essentially 

 the siune as E. laxus, the marked differences being in the cicatrices upon the 

 dorsum, which is also flattened — a feature not observed in the other species. 



The habit of the shell in attaching other objects is like the Tertiary and 

 recent genus Phorus, but, in all other respects, is similar to Euomphalus or 



