4 
58 CONCHOLOGIST’S COMPANION. 
eggs in small cavities on the outside of her shell, to 
which she attaches them by means of a glutinous 
substance: but it is not certain that the numbers 
which are often seen adhering, are all deposited by 
the inhabitant ; as this species of shell-fish, like the 
cuckoo, frequently appropriates a neighbour’s shell, 
for the temporary reception of her offspring. 
But to proceed with our compensations. A peculiar 
class of Muscles, the M. lithophagus, and M. rugosus, 
Burrowing and Rugged Muscles, possess the extra- 
ordinary faculty of penetrating coral, and calcareous 
rocks, and thus elude the vigilance of their marine 
enemies; nay, they are so firmly fixed in their holds, 
that it is impossible to extract them without break- 
ing the enclosing substance. Others congregate 
together in immense beds or layers, and others 
invariably attach themselves to extraneous sub- 
stances, by means of a coarse silky byssus. The 
works of the Deity are known by expedients. 
These extraordinary instincts prevent the total extir- 
pation of the species; for they furnish a supply of 
food to different kinds of fish, marine birds, and 
animals. 
But are not the Muscles defended with a testaceous 
coating? How, then, is it possible for a bird to 
open and devour them? These instinctive creatures 
pounce upon their prey, when left uncovered by the 
