TO GEOLOGY. 135 



P. Desnoyersii* Plate 4. Fig. 128. 



Description. Shell fusiform, turrited, closely and trans- 

 versely striate, slightly tuberculate on the superior whorls ; 

 substance of the shell rather thick ; spire elevated, pointed 

 at the apex ; whorls eight ; mouth two fifths the length of 

 the shell. 



Length .7, Breadth 5-20ths, of an inch. 



Observations. In outline somewhat like the last de- 

 scribed, but differing in the striae and tubercles. In the 

 Desnoyersii the transverse striae are disposed to alternate, 

 and are cut by almost imperceptible longitudinal stria3. 



P. Hceninghausii.-\ Plate 4. Fig. 129. 



Description. Shell fusiform, turrited, transversely striate, 

 furnished with two rows of longitudinal folds in zig-zag ; 

 substance of the shell rather thin ; spire elevated, acute at 

 apex; whorls ten, subcanaliculate above ; mouth rather 

 narrow, about one third the length of the shell. 

 Length .7, Breadth .4, of an inch. 



Observations. This species may be distinguished by its 

 double row of folds, which being placed, the superior one 

 obliquely to the right, the other to the left, produce a zig- 

 zag appearance. 



* Named after M. Desnoyers, advantageously known for his labours in 

 the Tertiary deposites. 

 t Named after the distinguished geologist of Crefeld. 



