UNIVALVES. 179 
Thus constructed, the Jeredo readily enters the 
stoutest timber, and insinuates itself into lofty vessels, 
which it destroys, like the evil genius so admirably 
pourtrayed by Captain Morris, whose visitations no 
earthly bulwarks could impede. 
** Care mounts Rideaux, with four-and-twenty pounders, 
Nor heeds our light troops, nor our Indian warriors, 
Swifter than moose deer, or the fleeter east wind, 
Pushing the crowds on.—” 
Imitation of Horace, Mon. Mag. 
The construction of this indefatigable insect, bears 
an obvious reference, as well to the purposes for which 
it is designed, as to the substance in which it is 
inclosed. The head is well prepared by nature for 
encountering difficulties, being surmounted with a 
helmet, and provided with a tooth, adapted for per- 
forating the hardest substances; the neck is also 
furnished with strong muscles, which materially 
assist the operations of the head; and the body is 
covered with a thin, transparent horn, through which 
its internal operations may be easily discovered. 
The shell is composed of carbonate of lime, and a 
gelatinous substance; greater in proportion than that 
of the Chama gigas, but considerably less than in the 
shell of the common Oyster. The heart is situated 
on the back, between the mouth and the lower 
part of the stomach; and admits of only a single 
nN 2 
