56 FIFTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



BELLEROPHON (BUCANIA) PELOPS (n.s.). 



Casts of this species occur in the limestone of the Upper Helderherg 

 group. 



The shell has been very rotund : the volutions, which have been three or 

 four, were exposed in the umbilicus ; the transverse diameter of the volution 

 is about twice as great as the length or dorso-ventral diameter, rounded on 

 the back, and abruptly bent into the umbilicus ; the aperture expands la- 

 terally, and is somewhat reniform, with a sinus on the dorsal side ; the back 

 is distinctly carinate on the last volution, and the surface has apparently 

 been marked by transverse striae. 



It is impossible to characterize the species^fully from the materials pos- 

 sessed, but it may be distinguished by its similarity of form to B. expa7isus; 

 but the dorsal carina on the cast of this one is more sharply marked, the 

 volutions are less compressed in the dorso-ventral direction, and the um- 

 bilicus is more abruptly depressed. 



Geological formation aiid locality. In the Schoharie grit at Schoharie, 

 and in the limestones of the Upper Helderberg group at Clarence-hollow, 

 N.Y.; and Brownville, Ohio. 



BELLEROPHON ACUTILIRA ( n. s.). 



Shell subglobose; the first volutions discoidal, and the body volu- 

 tion towards the aperture very ventricose; aperture expanded; 

 peristome moderately sinuate in the middle in front; spire closely 

 enrolled. 



Surface marked by regular and subequidistant striae, which, bend- 

 ing forward from the ventral edge of the volution, make a broad 

 curve on the side, and are abruptly bent backwards, making a 

 sharp (a -shaped) angle on the dorsal line, which is acute on the 

 upper part of the last volution, but becoming regularly convex, 

 with a less abrupt curvature of the striae upon the more expanded 

 part towards the aperture. 



In one specimen of this shell, I find characters corresponding to those 

 given by Mr. Conrad to B. hrevilineatus. The striae proceeding from the 

 umbilicus are well marked at first, but become obsolete on the side of the 

 volution, but are well marked again on the dorsum. This character obtains 

 only on the last half of the outer volution, and above this the striae are 

 uniform over the whole surface : the periphery is obtusely angular, but not 

 acute ; and it does not appear, therefore, that this can be identical with the 

 species of Conrad. At certain periods in the growth of the shell, the si- 

 nuosity in the anterior side of the peristome has been very deep and acute ; 

 but at a later period, the character has become gradually less extreme. 



[ September, 



