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 strie 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 
striz; 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 strize, which are very closely set over the whole body 
of the shell. In some specimens these striz 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 strie ; 
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 A, Breadth .2, of an inch. 
Observations. This species closely resembles the last 
