MOLLUSCS 85 



ornamentation in all countries, savage and civilised ; 

 pearls still have a considerable market value ; and from 

 the molluscs the ancients obtained some of their valued 

 dyes. Shells have played their part in religious customs 

 and beliefs and still do so in some countries. 



In the present volume only the marine forms will be 

 touched upon and it may be said that the seas appear to 

 have swarmed with molluscs of all descriptions from 

 remote periods, countless asons before the most primitive 

 of the vertebrate animals came into being. Without 

 entering into the complexities of scientific classification, 

 it may be mentioned that the molluscs are divided into 

 five main classes — each abundantly represented in salt 

 waters. 



Class 1. Group Amphineura. These molluscs, though 

 abundant, form one of the smallest classes and to the 

 casual observer are altogether unknown. It may have 

 chanced, however, that the seaside visitor whilst searching 

 for crabs or edible molluscs amongst the rocks, has been 

 nonplussed by certain creatures which although having 

 much the appearance of woodlice adhere to the rocks 

 with all the tenacity of limpets. These are the Chitons 

 or " Coat of Mail Shells." If one is prised from its 

 anchorage it will be seen that the animal is not unlike 

 a limpet in general shape, but has the shell divided into 

 eight overlapping sections, permitting the creature to 

 fold itself in half, thus protecting its defenceless under- 

 surface. Peculiar sense organs having each a retina and 

 lens are attached to the shell itself and the gills are seen 

 as a feathery fringe marginating the animal's body. Chitons 

 are very abundant, some attaining to large size, though 



