52 THE SHELL-FISH OF THE COAST. 



niollusk, and allowing the shells to accumulate on 

 these boughs for a period of several years. They 

 are then raised, the quantity sold by weight, and 

 distributed over the interior of the country. 



The muscle when first hatched is an active 

 free-swimming little creature, which attaches itself 

 when no larger than the head of a pin. But much 

 later in life it still possesses the power of disen- 

 gaging the attaching byssus, and securing a new 

 anchorage when such is needed. By alternately 

 passing forward its delicate threads, the animal 

 pulls itself along to a selected locality, much in 

 the manner that is adopted by many spiders in 

 securing their prey. 



Keadily distinguished from the edible muscle by 

 its rounded anterior outline and the plications or 



HOESE-MUSCLE. 



radiating lines extending down the sides of the 

 shell, is the so-called horse-muscle {Modiola plica- 

 tula), like the former an inhabitant of the shallows 

 about tide-water. Here, in the somewhat peaty 

 soil, they are frequently found burrowing in vast 

 numbers, so closely packed together as to form a 

 true stratum. The shells are often much eroded 



