ORDER TRACHELIPODA. 33 



retire into the deepest recess of its shell ; on this ac- 

 count it is without an operculum, which would evidently 

 be useless, as it would be lost at the same tinje as the 

 foot. 



The Harps, says Lamarck, are very beautiful shells, 

 and if they were less common, would, on account of 

 their elegant forms and colours, become valuable in a 

 collection. Some species, however, are still considered 

 rare. 



The Harps take their name from the fancied resem- 

 blance between the regularity and direction of the ribs 

 on the shell, and the strings of a harp. The species are 

 not numerous, not exceeding eight in number. 



The W iDE-Mov TUKD VvRvvR A, (Purpura patula.) 



This species of Purpura is said to be that which was 

 employed by the Romans in dyeing, but many others of 

 the same family yield a purple colouring-matter. It is 

 nearly three inches in length, and is found in the At- 

 lantic Ocean and the Mediterranean. 



The purple colour which this little Molluscous animal 

 produces, was discovered by the inhabitants of the an- 

 cient city of Tyre, and was thence called the Tyrian 

 purple. The circumstances which led to the discovery 

 of it arevery imperfectly known, but fiction has supplied 

 the want of historical facts, and described its origin 

 with sufficient minuteness of detail. According to one 

 account, the merit of its discovery is due to a dog be- 

 longing to a certain Hercules. We are informed that 

 when this dog was accompanying his master along the 

 sea-shore, who was then following the nymph Tyros, the 

 animal seized one of the Purpurse lying on the sand, 

 and breaking the shell with his teeth, his mouth soon 



