388 PLEUROTOMID^E. 



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 f Andrew) ; both sides of the 

 Mediterranean, the Adriatic, and ^Egean: 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 surface 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. brachystoma, P. nebula, 

 and P. l&vigata 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 striae 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 Raphitoma polita of Brusina. 



B. Operculated. 

 8. P. NIVA'LIS*, Loven. ^ 5-35- 



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



BODY milk-white : head prominent, and slightly cloven in 

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

 the middle beneath the tentacular membrane : tentacles very 



* Snow-white. 



