GASTEROPODA. 99 



specimen figured on plate 22, as well as others examined, are so far eroded or 

 exfoliated as to have lost the evidence of the dorsal band, and that they are in 

 fact the B. Newberryi. 



Bellerophon hyalina, n. sp. 



PLATE XXVI, FIG. 4. 



I 



Shell subglobose, rounded upon the dorsum, and very abruptly depressed into 

 the comparatively broad umbilicus. Body-whorl ventricose and rapidly 

 expanding. Aperture very wide, broadly reniform — the full extent 

 unknown ; margin undetermined ; the outer lip recurving at the sides, 

 and partially inclosing the broad umbilical depression, and spreading in a 

 thin callus over the columellar lip. 



Surface marked by somewhat distant, sharp, transverse striae which bend 

 backward as they approach the centre of the dorsum; and these are 

 cancellated by finer revolving striae. No dorsal band has been observed. 



The general aspect of the surface is like that of a young individual of B. 

 Leda, but the broad umbilicus, with the subangularity of the sides of the outer 

 volution are distinguishing features. The shell is silicified and crystalline, and 

 the surface-markings pretty well preserved. Although no dorsal band has been 

 observed, it is possible that such a feature may exist in better preserved 

 specimens. 



Formation and locality. In some decomposing cherty layers in the upper 

 part of the Upper Helderberg group, near Jamesville, Onondaga county, asso- 

 ciated with species of Loxonema, Pleurotomaria and of Coleoprion. 



The above association of species is, in many respects, extremely similar to 

 tli.it of the cherty beds at Dublin, Ohio. The species of Coleoprion is appar- 

 ently identical in the two localities ; and of the other genera, several of the 

 species are closely allied. 



