Industrial and Manufacturing Uses of Shells. 307 



ranean the fin-shells or sea-wings, as they are termed. 

 The species are the Pinna nobilis, etc. 



The shells, which are in general very fragile, resemble 

 in form those of the larger species of mussels, being long 



FIG. 23. 



i. Pinna nobilis. 2. Pinna rugosa. 



and tapering, narrow at the back, and gradually expanding 

 to a considerable breadth towards the opposite extremity. 

 There are some 20 or more species of the genus, which 

 produce in large quantities a very fine sort of silky byssus 

 or braid. It is called by the fishermen lana pinna, or fish- 

 wool. These bivalves are provided with a tuft of delicate 

 fibre, which cannot be better compared than to fine hair 

 or silk, or spun glass ; with this they attach themselves to 

 the rocks, living continually under water. 



