88 UNIVALVES. 



colour, sometimes banded with brown or yellow. 

 Length rarely exceeds two inches, breadth one. 



The animal that inhabits this shell has two 

 slender tentacula bearing eyes about half way 

 up on the outside, the ends of the tentacula as 

 far as the eyes are retractile * like those of snails. 

 Its mantle forms a tube through which it 

 breathes ; it has a foot with a horny operculum. 

 Near to its head, and lying in a little furrow, is 

 a white vein which yields a beautiful purple tint, 

 supposed to be that so long celebrated as the 

 Tyrian dye. In order to obtain this colour, the 

 vein is laid open with a needle, and is found to 

 contain a tenacious yellow matter like cream. 

 As soon as this fluid is put on any substance, as 

 silk, linen, &c. and exposed to the air, the yellow 

 assumes a brighter hue, but speedily turns to pale 

 green, then gradually becoming darker, until it 

 has obtained a blue cast, and from that it 

 changes to a purplish red, more or less deep 

 according to the quantity used. The succession 

 of the tints is accelerated by exposure to the rays 

 of the sun. The stain given by this animal fluid 

 seems to be indelible, bidding defiance to every 

 chemical process to obliterate it, and it might 

 therefore be most advantageously used as a 

 kind of marking ink. 



The Buccinum Lapillus is one of the most 

 common shells upon our coasts, adhering to 

 rocks quite up to high water mark. 



* Retractile, capable of being drawn back, from the Latin 

 re back, and tract us drawn. 



