TO GEOLOGY. 145 



and very distinct from any other herein described. Five 

 or six of the striae 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 striae 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 striae, 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 striae. 



jP. decussatus. Plate 5. Fig. 146. 



Description. Shell subtuibinate, cancellate, furnished 

 with seven or eight large transverse striae, cut by numer- 

 ous longitudinal small striae ; 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. 

 T 



