TO GEOLOGY. 155 



P. elegantissima. Plate 5. Fig. 161. 



Description. Shell subpyriform, alternate, beautifully 

 cancellate over the whole exterior ; substance of the shell 

 rather thin ; spire rather elevated, pointed ; suture small ; 

 whorls five, convex ; canal rather long ; mouth subovate, 



contracted ; outer lip . 



Length .6, Breadth .2, of an inch. 



Observations. One nearly perfect, and several fractured 

 specimens of this very beautiful species only have come 

 under my notice. Its delicate and graceful form and 

 highly adorned exterior render it very remarkable. It is 

 closely allied to the preceding species, but differs in having 

 a longer canal, in the absence of the angle on the su- 

 perior part of the whorl, and in being a much smaller and 

 thinner shell. In some of these characters it has a stronger 

 resemblance to the Pyrulanexilis (Lamarck). Like it, it is 

 without the angle. Its being more attenuate and having 

 a higher spire makes it specifically different. The reticu- 

 lation is, if possible, more perfect and beautiful than on the 

 cancellata. 



P. Smithii* Plate 5. Fig. 162. 



Description. Shell pyriform, smooth, ventricose, canali- 

 culate on the widest part ; substance of the shell very 



* I have placed to this species a name which will not soon be forgot- 

 ten to British geologists. The veteran geologist William Smith, was 

 almost a solitary labourer for many years in the field, and to him very 

 much is due for the present advanced state of the science of geology in 



