lANTHINA. 175 



offset or prong, so as to make the tentacles appear double or 

 forked : eyes either wanting or said to be in certain species very 

 small and indistinct and placed on the offsets of the tentacles : 

 foot narrow, elongated, rounded in front and tapering behind ; 

 'it secretes a large oblong foam-like apparatus, formed of air- 

 cells and serving as a float to keep the animal always buoyant : 

 gills 2, unequal in size. 



Shell shaped like a Helix, with a broad and imperforate 

 base, always of a purplish-blue or violet colour, but differently 

 tinted according to the species : epidermis none : spire short, 

 the last whorl being disproportionately large ; apex styliform, 

 and obliquely twisted on one side, but never heterostrophe : 

 mouth somewhat triangular, and wide ; lips disconnected : pillar 

 more or less straight, ending in an angidar point. No oper- 

 culum. 



Did Edmund Spenser ever see lanthince in their native 

 haunts ? or were they visible to his inner eye only^ when 

 he wrote,, 



" So likewise are all watr'y living wights, 

 Still tost and turned with continuall change, 

 Never abyding in their stedfast plights " ? 



Such is the wandering and restless course of the Ian- 

 thina, floating passively on the surface of the ocean, with 

 its shell downwards and its foot to the skies, the con- 

 tinual sport of winds and waves, and driven hither and 

 thither without choice, without hope of reaching any 

 goal. But woe to them if they approach the shore ! 

 That is not the haven where those sailors would be ; for 

 here they are inevitably wrecked and stranded : it is 

 thus that we claim one kind of lanthina as a product of 

 the British seas. 



The earliest notice which we find of this remarkable 

 moUusk, or " blue snail,'''' is in the ^ Opusculum de Pur- 

 pura ^ of Fabio Colonna (one of the many noble authors 

 whose writings are not less illustrious than their names) , 

 published at Rome in 1616. It contains a fair repre- 



