VIOLET SHELLS. 



a very peculiar mechanism, and furnished at its extremity with a 

 kind of file, by the aid of which they bore through the shells of 

 other Mollusca, notwithstanding the massiveness of the defensive 

 armour of their victims. Their eggs are very numerous, and are 

 generally enclosed in cases of complicated form and very curious 

 structure. 



The beauty, and more especially the rarity, of the shells of 

 many species have often caused them to bear a very high adven- 

 titous value. The elegant Chinese shell, known as the " Royal 

 Staircase " or Wentle-trap, derived its specific name (Scalaria 

 prctiosd) from the high price at which large and fine specimens 

 were sold. One was purchased in France for a hundred pounds 

 sterling, and in England from twenty to thirty pounds have been 

 given for a good specimen. The shell is now far from rare, and 

 shillings take the place of pounds in the purchase. 



FIG. 216. THE WENTLE-TRAT. 



The Violet Shells (Janthina) in their external appearance very much re- 

 semble our garden snails, and are not furnished with an operculum. Instead 

 of this, however, they possess a very curious apparatus attached to their rudi- 

 mentary foot, composed of a substance resembling horny froth, that serves as 

 a float, whereby they are sustained at the surface of the sea, and to which as 

 to a raft the Janthina fastens its eggs. These Mollusks are common in the 

 Mediterranean : on touching them they emit a violet-coloured fluid that dyes 

 the water around them of a deep purple colour. 



The Cone Shells (Gomes'} (Fig. 217) are remarkable for their conical shape 

 and the flatness of their spire, as well as for the extraordinary beauty and 

 brilliancy of their colours. These shells, in Africa, in regions far from the sea, 

 are considered of as great value as the Lord Mayor's badge is in London, and 

 are so highly prized as evidences of distinction, that for t\vo of them a slave 

 may be bought, and five would be considered a handsome price for an elephant's 

 tusk worth ten pounds. 



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