PLATE CXLT. 



In habit and manners of life this species greatly resembles the Pho- 

 lades, each forming for itself a separate apartment within the hard 

 clay, or solid stone : this it pierces when young, and afterwards con- 

 tinues to enlarge the cell as it increases in bulk, without widening the 

 aperture ; so that when full grown, the shell cannot easily be taken 

 whole out of the cell, without breaking the stone in which it is 

 contained. 



This shell may perhaps be arranged with equal propriety with the 

 My<s as the Mytili, notwithstanding that it is admitted among the 

 latter by most collectors. 



