520 RAZOR-SHELLS. 
vast plantations, as they may be called, of these creatures have increased to 
such an extent, that they threaten to obliterate several useful bays for all 
maritime purposes. : 
Soe _ THE family of the COCKLES, or Cardiadz, so called 
YOM from their heart-like shape, is well represented by 
uw the common COCKLE (Carazum edule) of our British 
shores. Generally, the Cockle is a marine animal ; 
but it sometimes prefers brackish water to the salt 
waves of the ocean. 
This mollusc frequents sandy be a8 donate 
p about low-water mark, burying itself in the sand by 
Te means of the powerful foot, which enables it to leap 
to a surprising height. 
WE now come to the well-known Solenidz or RAZOR-SHELLS, so called on 
account of their shape. ; 
These curious molluscs always live buried in the sand in an upright 
position, leaving only an opening shaped like a key-hole, which corresponds 
with the two siphon tubes. 
COMMON RAZOR-SHELL.—(Solen vagina.) 
These creatures are generally found at a depth of one or two feet, and 
when they make their burrows, as they are often in the habit of doing among 
the rocks, not even the hooked iron can draw them from their retreat. 
Pippock.—(Pholas dactylus.) 
WE next come to the Pholas. the best example of which is the common 
species popularly called PIDDOCK, and found in profusion along the sea- 
coast. 
The common Piddock may be found in vast numbers in every sea-covered 
chaik rock, into which it has the gift of penetrating so as to protect itself 
from almost every foe. 
Mr. Woodward remarks, very justly, that the “ condition of the Pholades is 
always related to the nature of the material in which they are found burrow- 
ing ; in soft-sea beds they attain the largest size and greatest perfection, whilst 
in hard and especially gritty rock they are dwarted in size, and all prominent 
points and ridges appear worn by friction. No notice is taken of the hypo- 
thesis which ascribes the perforation of rocks, &c., to ciliary action, because 
