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and boring marine animals. 
small argillaceous stratum, which a Saxicava rugosa has been 
unable to overcome. 
a , The stratum confining the shell. 
Fig. 7. The shell of a Saxicava rugosa which has been 
injured by another. The umbo has been removed, but the 
ligament and the cuticle, which extends from it to the ante- 
rior extremity of the shell, remain uninjured. 
Fig. 8. The animal of Saxicava rugosa ; the branchiae 
removed, the mantle divided and thrown back ; a , the sy- 
phon ; b, the posterior adductor ; c c, the posterior muscles of 
the foot ; d , the foot, with its tube and byssus ; e , the ante- 
rior adductor ; /, the opening in the mantle for the foot. 
The anterior muscles of the foot are concealed by the body. 
Fig. 9. Teredo palmulatus ; a a, the boring shells ; b, the 
foot ; c, the anterior adductor ; d, the process to which the 
posterior adductor is attached. 
Fig. 10. Teredo communis; the boring shells separated 
to show the posterior adductor, a , The ligament; b, the 
process to which it is attached ; c, the posterior adductor 
attached to one of its processes ; d, the corresponding pro- 
cess in the other valve. 
