220 
NATURAL HISTORY. 
these eight feet thus connected, six are short, and these are 
held up as sails to catch the wind in sailing : the two others 
are longer, and are kept in the water; serving, like paddles, 
to steer their course by. When the weather is quite calm, 
and the animal is pursued from below, it is then seen ex- 
panding only a part of its sail, and rowing with the rest : 
whenever it is interrupted, or fears danger from above, it 
instantly furls the sail, catches in all its oars, turns its shell 
mouth downward, and instantly sinks to the bottom. Some- 
times also it is seen pumping the water from its leaking 
hulk ; and, when unfit for sailing, deserts its shell entirely. 
The forsaken hulk is seen floating along, till it dashes, by 
a kind of shipwreck, upon the rocks or the shore. 
It may seem whimsical to make a distinction between the 
animal perfection of turbinated and Bivalved Shell-ftsh, ot- 
to grant a degree of superiority to the snail above the oys- 
ter. Yet this distinction strongly and apparently obtains 
in nature ; and we shall find the bivalved tribe of animals 
in every respect inferior to those we have been describing. 
The Muscle, as is well known, whether belonging to 
fresh or salt water, consists of two equal shells, joined at the 
back by a strong muscular ligament that answers all the 
purposes of an hinge. By the elastic contraction of this, the 
animal can open its shells at pleasure, about a quarter of an 
inch from each other. The fish is fixed to either shell by 
four tendons, by means of which it shuts them close, and 
keeps its body firm from being crushed by any shock against 
the walls of its own habitation. It is furnished, like all 
other animals of this kind, with vital organs, though these 
are situated in a very extraordinary manner. It has a mouth 
furnished with two fleshy lips ; its intestines begin at the 
bottom of the mouth, pass through the brain, and make a 
number of circumvolutions through the liver ; on leaving 
this organ, it goes on straight into the heart, which it pene- 
trates, and ends in the anus ; near which the lungs are 
placed, and through which it breathes, like those of the 
snail kind ; and in this manner its languid circulation is 
carried on. 
The multitude of these animals in some places is. very 
great ; but from their defenceless state, the number of their 
destroyers are in equal proportion. 
But notwithstanding the number of this creature s ani- 
mated enemies, it seems still more fearful of the agitations 
of the element in which it resides ; for if dashed against 
rocks, or thrown far on the beach, it is destroyed without a 
