TO GEOLOGY. 145 
and very distinct from any other herein described. Five 
or six of the strie on the widest part of the whorl have 
between each of them a very minute stria. 
F. Mortonii.* Plate 5. Fig. 145. 
Description. Shell subfusiform, furnished with large 
longitudinal folds, cut by transverse strie which are en- 
larged on the folds; substance of the shell rather thin ; 
whorls six, inflated, flattened at top, subspinous on the 
angle ; canal long and straight ; mouth subrotund ; outer 
lip sharp, within slightly crenate. 
Length .7, Breadth .3, of an inch. 
Observations. A very distinct species, and remarkable 
for its strong folds covered by transverse strie, which are 
so much enlarged on the folds as to give it a tuberculated 
appearance. On the angle of the whorl the superior 
stria is so much enlarged as to make the angle subspinous 
in perfect specimens—above it is without striz. 
F. decussatus. Plate 5. Fig. 146. 
Description. Shell subtuibinate, cancellate, furnished 
with seven or eight large transverse striz, cut by numer- 
ous longitudinal small striz ; substance of the shell thin ; 
suture deeply grooved ; whorls six, inflated, biangular in 
* To this species I have placed the name of the corresponding secre- 
tary of the Academy of Natural Sciences of Philadelphia, Dr Morton, 
who has done much to promote a knowledge of our geology. 
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T 
