388 PLEUROTOMID^. 



Guernsey (Gallienne) . The variety or smaller form 

 inhabits the coralline zone_, and occurs in the Channel 

 Isles also^ and on the coasts of Dorset^ Devon, and 

 Cornwall ; Connemara (Alcock) . North Atlantic_, from 

 Cherbourg (De Gerville and Mace) to Gibraltar,, and 

 westward to the Azores (M*^ Andrew) ; both sides of the 

 Mediterranean, the Adriatic, and iEgean: depths 2- 

 15 f. 



When the tide goes out this little mollusk burrows in 

 the sand, but not deeply, in a slanting position ; and it 

 rises to the sui'face when the tide comes in, like several 

 other univalves of similar habits. Dead shells thrown 

 up on a sandy beach, and rolled about by the waves, 

 become polished by the attrition and appear smooth. 

 The chief differences between P. brachy stoma, P. nebula, 

 and P. laevigata consist in the first being small and 

 cylindrical, and having some of the spiral striae larger 

 and more prominent than the rest; the second forms 

 an elongated cone, the spiral strise being equal in size 

 and more numerous; the present species is spindle- 

 shaped and smoother, the body- whorl is nearly ribless 

 (especially near the mouth) , and the suture is thickened 

 by a strap-like rim. 



This is the P. Metcalfei of Hanley^ and apparently 

 the Raphitom.a polita of Brusina. 



B. Operculated. 

 8. P. niva'lis*, Loven. 



r. nivale, Lov, Ind. Moll. Scand. p. 14. 



Body milk-wliite : head prominent, and slightly cloven in 

 front : mouth or proboscidal orifice knob-like, and placed in 

 the middle beneath the tentacidar membrane : tentacles very 



* Snow-white. 



