5I4 LIMPETS AND MAILSHELLS, 
most plentiful species of the British coasts, and may be found by hundreds 
either crawling among the sea weeds at low water, or flung upon the sands by 
the tide. The shell of this creature is beautifully pearly, and when the outer 
coating is removed the iridescent nacre below has a very lovely appearance. 
Jewellers and lapidaries employ these shells largely in their art, polishing 
them carefully and then stringing them together so 
as to form bracelets and necklaces, or affixing them 
as ornaments to various head-dresses. 
THE well-known univalves, so familiar under the 
am name of LIMPETS, are divided ino several families, 
LIMPET..—(/aéel/a 0M account of certain variations in the structure of 
vulgares.) the shell. The first family is termed Fissurellida, 
on account of the fissure which appears either at 
the apex or in the front edge of the shell. 
Allthe Limpets are strongly adhesive to rocks, 
as is well known by everyone who has tried to remove 
one of these molluscs from the stony surface to 
which they clung. The means by which the animal 
is able to attach itself with such firmness is ana- 
logous to the mode in which the suckers of the 
oo cuttle-fish adhere to the objects which they seize, 
iinpET the formation of a vacuum, and the consequent 
(Showing underside.) Pressure of the atmoshere, being the means em- 
ployed. The foot of the Limpet is rounded, broad, 
thick, and powerful ; and when the animal wishes to cling tightly to any 
substance, it presses the foot firmly upon the surface, and retracts its centre, 
while its edges remain atfixed to the rock. A partial vacuum is therefore 
formed, and the creature becomes as firmly attached to the rock as a boy’s 
leathern sucker to the stone on which he has pressed it. 
WE now cuime to the curious family of molluscs called appropriately 
Chitonide, or Mailshells, because their 
shells are jointed together like the pieces 
of plate armour. When separated from 
each other, the plates bear a strong resem- 
blance to the joint of a steel gauntlet, aud 
overlap each other in a similar fashion, 
a thick and-strong mantle taking the 
place of the leather. There are eight of 
es these plates, and all of them have a some- 
MARETET cHITON.—( Chiton what saddle-like shape. A similar arrange- 
ment may be observed in the lower ab- 
dominal plates of n-any beetles. Each of 
these plates is fixed to the mantle by certain rounded processes from their 
front edge, and when the plates are examined separately the processes will 
be plainly seen, white and pearly, as the interior of the shell. 
The Chitons are able to roll themselves up in a partial kind of manner, 
and present a curious resemblance to the well-known armadillo, or pill 
woodlouse. 
The illustration represents the MARBI! ED CHITON, arather prettily-coloured 
shell, its exterior being rusty red mixed with brown and yellow, and edged 
with brown. 
PASSING from the sea to the land, we come to those Gasteropods which 
breathe atmospheric air, and are furnished with respiratory organs suited to 
the element in which they live. 
The first family is that of the SNAILS, or Helicida, containing a vast 
murmoreus.) 
