GASTEROPODA. 107 



of growth, the sinuosity in the anterior side of the peristome has heen very 

 deep and acute ; but at a later period, this character has become gradually less 

 extreme, and the striae of growth make a distinct curve on that part of the 

 shell. 



This species bears much resemblance to the Belhrophon Murchisoni of 

 d'Orisigw, but is more robust, with a greater width on the posterior side of 

 the aperture and a wider umbilicus. 



Formation and localities. In the shales of the Hamilton group, at Hamilton 

 and Pratt's Falls, in Madison county ; on the east shore of Cayuga lake, near 

 Norton's Landing ; and at York in Livingston county. 



Bellerophon brevilineatus. 



PLATE XXVI, FIGS. 8,6 7. 

 [1] Bellerophon breriliveatus, Conrad. Jour. Acad. Nat. Sci. Phil., vol. 8, p. 269, pi. 16, %. 6. 



Shell thin, ovoid, trumpet shaped, the outer volution rapidly enlarging 

 expanded at the aperture and sinuate in front; the dorsum elevated into 

 a distinct carina, and limited on each side by a sinus, which separates it 

 from the body of the volution. Umbilicus open and comparatively wide. 



Surface marked by simple concentric striae, which proceed pretty directly from 

 the umbilicus, and gently arching over the sides of the volution, where 

 they are often interrupted or obsolete, bend abruptly backward into the 

 sinus, and thence sharply arch over the carinate dorsum. 



In many specimens the striae are interrupted, becoming obsolete beyond 

 the middle of the sides of the volution, and do not continue into the sinus 

 between the body of the shell and the carina, though reappearing upon the 

 dorsum. 



This feature corresponds essentially with the description and figure of B. 



hnrilinratus, as given by Mr. Conrad, which is as follows: 



" Discoidal, tapering gradually to a very acute periphery ; volutions exposed ; 

 from the margin of the umbilicus radiate short lines, less in length than half the 

 width of the large volution." 



