CHAPTER III.—MusseEts. 
The mussels are oblong shells with two equal valves, covered 
Fig. 7. Mytilus edulis, var. 
pellucidus, 
with an epidermis, and hay- 
ing two adductor muscles. In 
the true mussels or Mytilide 
the adductor muscle nearest to 
the beaks is very small, and 
the hinge practically without 
teeth. They live attached 
Fig. 6. Mytilus edulis. 
to wooden piles or anything convenient, by a cord composed 
of strong threads. This cord is called the ‘* byssus.” 
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