IV INTRODUCTION. 



earth and the extraordinary changes it has undergone ; for, 

 as Bergman elegantly says, " fossil shells, coral, and wood 

 are the only three remaining medals of Creation." He will 

 see in the innumerable quantity of these animals, succeeding 

 each other from generation to generation in the depth of the 

 seas, one of the evident causes of the growth and increase 

 of islands and continents. 



But man may find in the knowledge of Mollusca applica- 

 tions still more direct to his well being in society, both as to 

 the advantages and disadvantages to be derived from them : 

 thus a great number of species are proper for food, as oys- 

 ters, muscles, &c., which are objects of commercial specula- 

 tions. The Pinna furnishes the Italians with materials for 

 a rich dress, and the pearl, so much prized by the Orientals, 

 by princes, and particularly by the ladies, as a modest and 

 beautiful ornament, is produced by a disease of the animals 

 in certain species of shells. It was this knowledge which 

 made the celebrated Linnaeus imagine that it was possible 

 to form an artificial pearlery in the rivers of Sweden. The 

 mother of pearl, so much employed as an ornament in arti- 

 cles of luxury, is only the interior lining of certain univalve 

 or bivalve shells. Painting draws from some of these ani- 

 mals many colours, valuable not so much for their beauty 

 as their usefulness, as Chinese ink and sepia. 



The brightest and richest colour known by the ancients, 

 and used by them for the celebrated Tyrian purple die, is 

 produced by animals at this time known by the name of 

 Purpura. 



The Teredo attacks the wood of our vessels, and often 

 does much injury ; therefore the knowledge of its manners. 



