372 THE OCEAN WORLD. 
in a vertical position, the larger side of their shell being uppermost. 
They are found on sandy bottoms in considerable numbers. The 
byssus has in all ages fixed the attention of the Mediterranean fisher- 
men upon these curious shells. With its tuft of fine silky hairs, six or 
seven inches in length, of a fine reddish-brown hue, articles of luxury 
are formed, which are often mentioned-by the Latin writers. The 
threads of the byssus, which are remarkable for their unalterable 
colour, were formed by both Greeks and Romans into a fabric to 
Fig. 167.—Pinna nobilis, with its byssus (Linnzus). Fig. 168.—Pinna bullata (Swainson). 
which there is nothing analogous in the world. The Maltese and 
Neapolitans still fashion soft tissues from it, but the stuffs so 
manufactured are mere objects of curiosity. 
Some thirty species are described as living in the several seas. 
Pinna nobilis (Fig. 167), the byssus of which was employed in the 
ancient Neapolitan industry, inhabits the shores of the Mediter- 
ranean. Pinna budla‘a, Swainson (Fig. 168), is also a well-known 
species. 
Our twenty-first family, Ostreide, contains the genera Lima, 
Spondylus, Pecten, Anomia, and the all-important genus Ostrea. 
