MonograpJi of the Gasteropoda. 307 



both in length and breadtli ; inner volutions comparatively small ; dor- 

 sura angulated and strongly keeled ; outer lip, rapidly expanding in a 

 rounded outline upon each side of a shallow sinus, curving abruptly at 

 the point of greatest expansion, and, with the inner lip, forming a line 

 nearly at right angles with the plane of the volutions ; inner lip thick- 

 ened and bearing a prominent node in the middle ; surface nearly 

 smooth in the specimens examined, but faint traces of fine lines may 

 be observed, curving with the shape of the shell downward from the 

 sinus, at the outer edge of the expanded aperture. 



Aperture two inches in breadth, while the body whorl, just at the 

 commencement of the expansion, is only one half inch across it in the 

 same direction. 



This species is remarkable for the strongly carinated dorsum, and for 

 the great expansion of the aperture in proportion to the size of the 

 inner whorls composing the body of the shell. 



The specific name is given in honor of Paul Mohr, Sr., of Cincinnati, 

 an experienced and extensive collector of fossils and minerals, and 

 member of the Cincinnati Society of Natural History. 



I found the species at Richmond, Indiana, in the upper part of the 

 Cincinnati Group, associated with Cypricardites Hainesi 



Genus Bucania—(HAhL, 1847). 



\_Etijm. — Bukane, a trumpet ; from the form of the shell.] 



Convolute ; spire equally concave on either side ; volutions in the 

 same plane, all visible, outer one ventricose, inner ones usually angu- 

 lated on the edge, concave on the ventral side ; aperture rounded- 

 oval, somewhat compressed on the inner side by contact with the next 

 volution, laterally and dorsally abruptly expanded. 



It diflTers from Bellerophon, in having all the volutions visible, and 

 gradually increasing in size. 



Bucania expansa — (Hall, 1847). 



Convolute, trumpet shaped ; volutions three, subangular, the last 

 one elongated, rapidly enlarging and abruptly expanded at the aper- 

 ture ; aperture broadly semi-circular, or sublunate, with a sinus at the 

 dorsal side ; dorsal line obtusely carinated ; section of the last volu- 

 tion, below the aperture, subtriangular ; of the inner volutions, sub- 

 elliptical, with the extremities obtusely angular ; original surface 

 striated. 



