MOLLUSCA. 143 



colour, only worn by kings and nobles, was the 

 produce of a sea-snail. 



Many rather marvellous tales have been related 

 concerning the origin of this purple dye of the 

 ancients. At the present time, all that appears to 

 be known with certainty is, that its discovery was 

 made at Tyre, and that it was produced by certain 

 sea-snails. Some writers assure us that the species 

 which furnished the colour were Murex brandaris 

 and Purpura lapiUus (Fig. 13) ; of which the first 



FIG. 13. Purpura lapillus (Purple-producing Whelk). 



produced the finest and most expensive colour, and 

 the latter, which is as common on the English 

 coasts as upon those of the Mediterranean, is a kind 

 of whelk. 



The liquid which can be squeezed out of this 

 whelk is colourless, or nearly so ; but by the action 

 of light it becomes first of a citron tint, then pale 

 green, emerald green, azure, red, and finally, in about 

 forty-eight hours, a magnificent purple. To enable 

 the colouring matter to take successively all these 

 tints, it must not be allowed to dry. 



