PLATE CLXXI. 



Gmelin, in his edition of the Sy sterna Natura^ neglects to insert 

 this species, for what reason we are at a loss to conceive. The 

 specimens we possess of this rare shell, from the warmer parts of 

 Europe, are larger than those found on our coast. In different 

 specimens we observe that the striae are liable to vary both in form 

 and number, some shells appearing much more strongly reticulated 

 than others. 



