130 SEA-SHORE LIFE 
ing the foot upwards, and attaching themselves successively 
higher and higher up by means of newly formed byssus threads. 
When the tide is high the valves of the mussels will be seen to 
be gaping, and the beautifully 
fringed edges of their mantles 
protruding slightly, allowing 
water and minute organisms to be 
drawn into their gill cavities, and 
from thence into their mouths at 
the opposite end of the shell. 
There are two adductor muscles 
Fig. 90; gaa ae se Cape instead of one, as in the oyster, 
but in most respects the anatomy 
of the mussel closely approaches that of the oyster. In France the 
mussels are cultivated and highly esteemed as food, and the fishery 
is worth more than $150,000 annually. We make very little use 
of our mussels, as at times they are said to be more or less poison- 

ous; especially those found growing upon wood. An account of 
the development of the edible mussel is given by John Wilson in 
“Fifth Annual Re- 
port of the Fishery 
Board for Scot- 
land,” for 1886. 
The Ribbed 
Mussel, ( Modiola 
plicatula, Fig. 91), 
can be disting- 
wished by the radi- 
ating ridges of the 
shell. It isa brack- 
ish water species 
and is found between tide limits from Nova Scotia to Georgia. 
* The Horse Mussel, or Bearded Mussel, ( Modiola modiolus, F1q. 
94), lives half buried in gravelly bottoms, or firmly attached by its 
byssus threads within crevices of rocks, below low-tide level. It 
ranges from New Jersey to the Arctic Ocean, and the northern 
coasts of Europe. It is chestnut brown, and the skin flakes off 
around the edges of the shell, forming a shaggy yellow “beard.” 

Fig. 91; RIBBED MUSSEL. 
*An illustration of the Horse Mussel with scale limpets and egg cocoons of Rock Snail, on 
page 143. 
