GASTEROPODA. H5 



distant striae. Approaching the anterior and lateral margins, the stronger 

 sharp striae become obsolete, leaving the surface marked only by the 

 simple striae of growth. 



This is a small species, attaining about half an inch in length. It is quite 

 rare : no specimen seen has shown the interior of the aperture, or the colu- 

 mellar lip. It may be readily distinguished from any other described in the 

 formations under consideration by its general form, the simple, sharp, trans- 

 verse stria;, and the comparatively wide dorsal band, which is marked by striae 

 as on other parts of the surface. 



In general form and surface-markings this species corresponds with B. 

 vasulites of Moxtfort, as figured by Ferussac and d'Orbigny, but differs in the 

 open umbilicus as well as in other details. It may also be compared with 

 B. hiulciis of Martin. In form it is quite similar to the young of B. Leda; but 

 in that one the revolving striae are always present, and usually more conspicu- 

 ous than the transverse striae. 



Formation and localities. A single specimen has been found in the shales of 

 the Hamilton group in each of the following localities : Near Norton's Landing 

 on the east side of Cayuga lake ; below Monteith's Point on Canandaigua lake; 

 and at York in Livingston county, N. Y. 



Bellerophon rotalinea, n. sp. 



PLATE XXVI, FIG. 8. 



Shell small, discoid. Volutions gradually expanding to near the aperture ; 



umbilicus open ; sides of the exposed volution depressed towards the back, 



and marked by a revolving sinus, leaving a prominent dorsal ridge. 

 Surface marked by distinct and sharply defined revolving striae, which are 



distant from each other about twice their width. No concentric striae 



are visible on the specimen examined. 



This small species is quite distinct from any other known in these forma- 

 tions. The discoid form with open umbilicus, revolving striae, and absence, so 

 for ;ts visible, of all other surface-markings, are characteristic features. It has 



