14 



Shell Life 



one per cent, of the shells contained a pearl, and that 

 only one pearl in a hundred had any great value. 

 The best of these, very regular in form, clear in 

 colour, and the size of a pea, would be worth £3 

 or £4. 



The Swan Mussels (Anodonta), of which we have 

 two forms, are less regular in outline than the Pearl 

 Mussels, and are, as their scientific name indicates, 







-—t 



in Mussel — end view 



practically toothless, though the hinge - teeth are 

 represented by sharp ridges on the valves. I have 

 already described their structure in the Introductory 

 Chapter. They occur in similar situations to those 

 affected by the Pearl Mussels, but are more generally 

 distributed throughout Great Britain. The large 

 Swan Mussel {A. cygnea) has an oval shell, but 

 with a straiofht hinofe-line, and with the beaks 

 placed well away from the centre, forward. The 



