58 FIFTEENTH REPORT ON THE CABINET OF NAT. HISTORY, 



marked by strong transverse arching ridges wliicli are closely 

 arranged, but, approaching the aperture, they become irregular, 

 and more distant from each other : the expanded portion has 

 two or three strong folds or wrinkles parallel to the margin of 

 the peristome, which are stronger in front and become obsolete 

 on each side of the expansion. The sides of the last volution are 

 marked by longitudinal ridges w^hich reach nearly to the margin 

 in front, but in some parts are irregular and obscure. 



This shell resembles in form the B. patulus, but is more robust, the 

 transverse stride stronger, and the concentric folds on the expanded portion 

 of the shell, as well as the longitudinal ridges on the sides, are characters 

 not possessed by that species. The transverse diameter is about one inch 

 and three-fourths, and the longitudinal diameter one inch and a half. 



The B. patulus and B. rudis, in the broad posterior expansion of the 

 peristome, which is not joined to the volution, resemble the Phraqmo- 

 STOMiE, to which genus they may belong. The large size and rotundity of 

 the volution beyond the aperture, in the absence of positive knowledge of 

 the interior, has induced me to place them under Bellerophon. 



Geological formation and locality. In the coarse shales of the Hamilton 

 group at Fultonham, Schoharie county, N.Y. 



BELLEROPHON LEDA (n.s.). 



Shell subglobose, a little flattened upon the dorsum. Body-whorl 

 ventricose : aperture very wide; peristome abruptly spreading 

 and broadly sinuate in front, with sometimes a deeper notch in 

 the middle. 



Surface marked by strong longitudinal or revolving striae, Avhich 

 alternate in size, and are often finer and more numerous on each 

 side of the dorsal band. Tlie revolving strise are cancellated by 

 finer transverse stride. On the dorsum there is a narrow band 

 which is not elevated, or sometimes scarcely raised above the 

 surface, marked by two or three revolving strise, and upon which 

 the transverse strise make an abrupt retral curve. In the exfolia- 

 tion of the shell, and even in the best preserved specimens, the 

 elevated transverse strise sometimes become obsolete towards the 

 aperture; and the revolving striae, becoming obsolete also, leave 

 a border marked only by the striae of growth. 

 The usual length of the shell, as seen in the calcareous shale, is 



about half an inch, with a width of about five-eighths of an inch; 



[ September, 



