3 



it and the upper fiiell internally. In fhape it fo exa(5llj'' re- 

 prefenrs the Patella antiqnati inverted, that had it been 

 found feparate might readily have been taken for it, being 

 pofienbd of fimilar tranfverfe wrinkles, and the margin 

 floping to one fide, and when deprived of the epedermiSy is 

 white. 



The operculum confifts of four valves, the poflerior pair 

 longeli, and a little hooked forward : the anterior pair is 

 rouffh vvitli JccuITated y//7(^ ; colour liviU-brown, jjurplifli 

 towards the points of the fummit. Length half an inch ; 

 breadth rather Icfs. 



The habitat of this fhell ( which without allowing a little 

 latitude in generic chara61;er, would not find a place either 

 amongfl tlie Balanus or Lepas, not being fefile nor pedun- 

 culated) is exueinely curious; it is found enveloped, or 

 bedded in a particular fpecies of fponge, expofing nothing 

 but the points of the operculum. 



The fponge is fomewhat allied to Sp07igea ttibulqfa,pYohei- 

 bly a variety, but coarfer in its texture, and not fo regularly 

 tubular as that figured by Ellis ; nor do we find it amongft 

 the ZoopMU's of that naturalifl, although common on the 

 weftern coaft. 



Amongft the reticulated fibres of this fponge the Balanus 

 finds a fecure lodgement in its infant flate, and is foon en- 

 clofed by the growing fabric of the fponge animal, except a 

 fmall opening, which is kept clear by the vortex occafioned 



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