112 ? A LJSONTOLOQ Y OF NEW YOU K. 



there are all gradations from this condition to those where the transverse arch- 

 ing stria} are scarcely or not at all visible, and the band is marked only by the 

 three, four or five sharp revolving striae. The extremes of this feature are not 

 fully shown in the figures. There is also a great variation in the character of 

 the revolving stria}, which are sometimes almost equally alternate in strength, 

 while in other examples there are fascicles of coarser and finer, or there is a 

 single strong and prominent one separated by three or four which are finer and 

 subdued, as illustrated in fig. 6. 



The outer volution is comparatively small and prominent at its junction 

 with the peristome, as shown in fig. 2, from a specimen which has not suffered 

 from pressure. Fig. 3, showing the umbilicus, is also from a specimen not 

 distorted by pressure. The pustulose character of the columellar lip is very 

 similar to that of B. patulus, but less strongly marked, as the species is less 

 robust, and this part of the fossil is rarely exposed. The species is well marked 

 and readily distinguished from any other in the New York formations except 

 B. Lyra, to which it bears much resemblance ; but authentic specimens of that 

 species are less ventricose and more evenly expanded at the sides, and the 

 width does not so greatly exceed the length. At the same time, the study of 

 a larger number of specimens has shown the possibility of a gradation of form 

 from one to the other, as may be inferred from a comparison of figs. 9 and 

 10 with figs. 19 and 20 of plate 23. 



This species occurs with B. patulus in several localities throughout the State, 

 but is far less numerous than that form. It resembles in form and surface- 

 markings the B. decussatus of Fleming, B. elegatis and B. clathratus of d'Orbiont, 

 and B. cancellatus of Hall. 



Formation and localities. In the Hamilton group, at Fabius, Delphi and Pratt's 

 Fall-, in Onondaga county ; at Sherburne creek ; on the east side of Cayuga 

 lake ; on the shore of Canandaigua lake ; at Darien ; and at Hamburgh and 

 Eighteen-mile creek, on the shore of Lake Erie. 



