Monograph of the Gasteropoda. 315 



It is known in the Cincinnati Group only in the form of casts, but 

 these so nearly resemble the description that no doubt seems to be en- 

 tertained about the identity of the species. It has a wide range, 

 being nearly coextensive with the group, and is reasonably abundant 

 in many localities. It is a common fossil. 



Murchisonia gracilis — (Hall, 1847). 



Slender, elongated ; volutions not less than ten, ventricose, suban- 

 gulated on the middle, very gradually increasing in size from the apex 

 toward the aperture ; surface marked by a carinal band upon the cen- 

 ter of the volution, with curving stride above and below. Casts of the 

 shell are entirely free from the anguhir carina. 



This fossil is likewise known only in the form of a cast in this local- 

 ity, with from six to eight volutions. Its range is veiy extensive, but 

 it is not remarkably abundant. 



Murchisonia hicincta — (Hall, 1847). 



Obliquely subconical ; spire elevated, acute ; volutions four or five, 

 angular, rapidly enlarging toward the aperture ; last one ventricose 

 below, tricarinate, the lower carina hidden by the suture of the next 

 volution at the upper inner angle of the aperture ; central carina on 

 the outer angle of the volution, margined on either side by a sharp, 

 elevated line, with a narrow groove between, producing a double spiral 

 band; aperture oblong, angulated below; surface marked by fine, 

 sharp stripe, which bend gently backward, and are but slightly un- 

 dulated in passing the first carina, from whence they turn more sud- 

 denly backward to the mesial band, making an abrupt, retral angle, 

 and then bending forward below, pass in a vertical direction to the 

 suture. In the last volution, the striae pass vertically to the lower 

 slight carina, which corresponds with the suture in the other volution*), 

 and from thence bend slightly backward, curving into the umbilicus. 



The specimens referred to this species are usually mere casts ; 

 sometimes, however, part of the shell is preserved, but the finer strife 

 I have never seen. Its range seems to be confined to the lower part 

 of the Cincinnati Group, probably not found over 300 feet above low 

 water-mark. 



Genus Fusispira — (Hall, 1871). 

 Shells fusiform, imperforate, spire more or less elevated, with rounded 



