584 
COWRY. 
acquire solidity by means of the external layers, which 
the animal applies after the mouth is not only formed, 
but considerably contracted, and furnished with the 
rudiments of teeth. The last coats proceed, as we 
have already said, from a transudation from the wings 
of the animal, and leave upon the convex surface of 
the shell the marks of the manner in which they 
are formed. This is by a longitudinal line, which 
may be plainly seen, and which divides them into 
two unequal parts. This line (made by the junction 
of the wings of the animal) plainly indicates, by the 
faintness of the tint, that the colouring juice was 
wanting in this part. It is a simple straight line, 
when the edges of the wings are of the same confi- 
guration, but passes in a sinuous or waving direction, 
as in the Cyprcea mappa, when the same edges are 
fringed or irregularly cut in their contours. 
The most interesting part of the history of these 
animals, and what may be considered as a very sin- 
gular phsenomenon, is their ability to quit their shells 
when they are no longer capacious enough to con- 
tain them, and to construct others better suited to 
their purpose. The animal increases in size while 
it is completing its shell, till at length it grows too 
large for its habitation, which, when finished, no 
longer admits of enlargement. Thus straitened for 
room, it is obliged to quit its old dwelling and build 
a new one of larger dimensions, and better propor- 
tioned to the increased size of its body. We are 
at a loss to say how this operation is performed; but 
we may suppose it is not a very laborious one, since 
