PINNA. ORDER MYTlLACEyE J MUSSELS. 405 



remarkable for its suppleness and warmth. The filaments are 

 extremely fine, of perfect equality of diameter through their 

 whole extent, of great strength, and of a brilliant and unalterable 

 reddish-brown colour. The ancients were acquainted with this 

 sort of stuff; but, in- consequence of the diminution in the 

 number of animals, it is becoming very scarce ; and, from its 

 expensiveness, it is little more than an object of curiosity. 



ORDER IV. -MYTILACE^E. 



946. In all the Mollusks of this order, there is a foot, which 

 some species employ for locomotion, whilst in others it serves 

 merely to draw out, direct, and fix the byssus. There are also 

 two adductor muscles, of which the anterior one is often very 

 small. The Mussels, properly so called, abound on the rocks of 

 our own coasts, to which they are fixed by their byssus ; and 

 they are often closely impacted together. Although in ordinary 

 circumstances they have no tendency to change of place, they 

 seem possessed of a certain degree of locomotive power. Reaumur 

 mentions, that in the saline marshes on the sea-coast, where the 

 fishermen throw the Mussels at hazard, they are found at the 

 end of some time united into packets. By putting them into 

 glass vessels, he observed that their mode of progression con- 

 sisted in thrusting their tongue-like foot out of the shell, curving 

 it, hooking it to some adjacent body, and thus drawing them- 

 selves forward to the point of attachment. Although Mussels 

 commonly afford a very wholesome supply of food, they some- 

 times acquire very poisonous properties. How this is to 

 be accounted for, is yet uncertain. Many instances have 

 occurred, in which a large number of persons have been suddenly 

 attacked with violent symptoms, after eating Mussels from a 

 particular bed ; and fatal cases have not been uncommon. Whilst 

 Mussels in general attach themselves to the surface of rocks, 

 &c., others appear to seek out hollows, and imbed themselves 

 there. Others form excavations for themselves in mud ; and 

 are found in spots which are occasionally left dry by the tide. 



