188 BIVALVES. 



OBSERVATIONS ON THE SHELL AND ITS 

 INHABITANT. 



The Pinna seems to form the connecting link 

 between the univalves and bivalves, for though 

 composed of two valves, it is incapable of mo- 

 ving on its hinge. It is generally found at a small 

 distance 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 tint. The animal possesses 

 a kind of tubular instrument, furnished with a 

 gland which secretes a glutinous substance : by 

 means of a slight pressure, a drop of this liquid 

 is 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 beau- 

 tiful 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 consists 

 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 



