PINNA-SEA WING. 193 



between the univalves and bivalves, for though 

 it is composed of two valves, they are so com- 

 pletely united that it is incapable of moving on 

 its hinge. It is generally found at a short dis- 

 tance from the shore, fixed in the mud at its 

 smaller end, and standing erect. The animal 

 forms a byssus, the fibres of which are aggluti- 

 nated either to the sand, gravel, roots of marine 

 plants, broken shells, or any matter within its 

 reach. The byssus of the Pinna is much more 

 fine and delicate than that of the muscle ; the 

 filaments are long, silky, and of a bright lustre ; 

 the natural colour is of a rich golden brown, but 

 it readily receives any artificial tint. The animal 

 possesses a kind of tubular instrument, furnished 

 with a gland which secretes a glutinous sub- 

 stance : a slight pressure occasions a drop of this 

 liquid to be deposited on the spot, to which the 

 byssus is to be attached ; by the retraction of the 

 foot, a silken filament is drawn out, and this 

 operation being repeated some thousands of times, 

 a beautiful tuft of silky fibres, is produced. The 

 Pinnae are much sought after on the coasts of 

 Sardinia and Corsica for the sake of the byssus ; 

 they are fished up with an instrument which con- 

 sists of two semicircular bars of iron fastened 

 together at each end, but three inches distant 

 from each other at the centre. At one end is a 

 hollow handle, in which a pole is fixed, at the 

 other is a ring, to which a cord is fastened. 

 When a Pinna is discovered, the iron is let down 



