THE MANTLE-COVERED ANIMALS. 113 
goes boldly out into the sea, and you will not wonder 
at its activity when you see its beautiful jewelled eyes 
(e) set all round the rim of its mantle like precious 
stones set in a ring. You may easily see these eyes 
peeping out at you through the half-opened shell in 
any fishmonger's shop, and a pretty sight it is. 
The life of the cockle (C, Fig. 42) is very different. 
True he can leap to a great distance by bending his 
long foot (/) and straightening it with a jerk ; but 
he uses it chiefly to burrow in the soft sand, and then 
he draws his body down till only the tip of his shell is 
uncovered, and there he takes in water and food. 
Some cockles have the two flaps of their mantles 
joined together and drawn out on the side opposite 
the foot into two short tubes (si, Fig. 42), down one 
of which the water enters, while it is thrown out at 
the other. 
Lastly, the razor -fish, whose shells \\e find so 
often, but whose bodies we rarely see, scarcely ever 
come above ground at all, but burrow with their thick 
foot till only the two siphons (si) are uncovered, and 
throw up jets of water, by which the fishermen find 
them when they dig them up for bait. 
We have bivalves then lying fixed in the deep 
water, anchored on the stormy shore, and buried in 
the sand, nay more, if we search at low tide we may 
often find the rocks riddled with holes, and, on break- 
ing them open, see within a Pholas, an animal like the 
razor-fish, but much shorter and with a beautiful deli- 
cate shell. The Pholas has learnt to find a home in the 
solid rock, while the groynes of our shores and the 
bottoms of our ships are destroyed by another true 
bivalve, the Teredo, which is miscalled a " shipworm." 
