114 PALEONTOLOGY OF NEW YORK. 



there are none from the same region having the characters of B. Leda. A 

 specimen, however, from the shore of Cayuga lake, referred to the latter 

 species, has an unusually narrow form with flattened subequal striae, and one 

 and sometimes two slender linear striae implanted between the larger ones — in 

 these characters being essentially identical with B. Lyra. In this example 

 the expanded part of the volution is marked by fine transverse lines of growth 

 without elevated striae, while the posterior part of the same is marked by 

 prominent transverse striae as in ordinary specimens of B. Leda. Possibly this 

 condition may be due in part to exfoliation, but the finest surface-markings 

 are preserved. When such varying conditions exist on the surface of the 

 same specimen, it is easy to believe that individuals of the same species, 

 living among the coarser sediments in the eastern part of the Hamilton area, 

 may, from the influence of physical causes, have assumed different characters 

 from those occurring in the western portion of the State. From the more 

 eastern localities we do not know a single specimen of B. Leda associated with 

 this species. 



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

 Fultonham, Schoharie county. One specimen only, shown in fig. 1, was found 

 among the collections of Dr. Knapp, from the rocks, of the age of the Hamilton 

 group, at the Falls of the Ohio. 



Bellerophon Helena, n. sp. 



PLATE XXIV, FIG. 11. 



Shell small, subovoid-hemispheric ; outer volution rapidly enlarging, auriculate 

 at the sides, ventricose ; umbilicus exposed. Aperture widely expanded, 

 broadly reniform, with the peristome spreading laterally, and sinuate in 

 front. 



Surface marked by sharply elevated, rather distant, concentric striae, which 

 curve very gently on the sides of the volution, and are somewhat abruptly 

 bent backward as they approach the dorsal band ; band comparatively 

 wide, distinctly limited on each side, and marked by the retrally curving 



