TO GEOLOGY. 147 



Observations. This beautiful little species is more slen- 

 der than any here described, and its mouth is more con- 

 tracted. The longitudinal folds being smaller on the 

 superior whorls, and the striae being there rather large, 

 cause these whorls to be cancellate. 



F. crebissimus. Plate 5. Fig. 149. 



Description. Shell subfusiform, furnished with longitu- 

 dinal folds cut by rather rough, very closely set transverse 

 striae ; substance of the shell thick ; spire rather elevated ; 

 whorls seven, convex ; canal rather short ; mouth sub- 

 rotund ; outer lip finely crenate, within dentate. 



Length .5, Breadth .2, of an inch. 



Observations. This species is remarkable for its trans- 

 verse striae, which are very closely set over the whole body 

 of the shell. In some specimens these striae are somewhat 

 rough, and present a slightly imbricate appearance. 



F. magnocostatus. Plate 5. Fig. 150, 



Description. Shell subfusiform, furnished with large 

 longitudinal folds, cut by transverse rather large striae ; 

 substance of the shell rather thick ; spire somewhat 

 elevated, acute at apex ; whorls six, convex ; canal short, 

 oblique ; mouth subrotund ; outer lip slightly crenate, 

 within dentate. 



Length .4, Breadth .2, of an inch. 



Observations. This species closely resembles the last 



