192 THE WORLD OF THE SEA. 
disaster of an inundation, caused by a contemptible mollusk. A 
closer study of the habits of this animal has shown that it pos- 
sesses an insurmountable antipathy to iron-rust; hence, all wood 
which is to be exposed to sea-water is first soaked in a solution 
containing iron. The covering of copper with which ships are 
armed, renders the appellation Linnzus gave to the teredo— 
Calamitas navium—no longer true. 
The body of the teredo is long and worm-like; its colour is 
THE COMMON TEREDO. 
(Teredo navalis.) 
greyish white. At one end is a knot, improperly called its head, 
and the other extremity bifurcates into what may be called two 
tails. It often attains the length of eight inches. It buries itself 
in a case which it eats out of the wood; the walls of the case 
are covered with a coating of a calcareous matter mixed with 
mucus—this renders them firm and solid. The round part of the 
mollusk carries two small valves, very thin and fragile; they are 
not unlike in shape to two halves of a nut-shell. These valves 
are immovable, and protect the weak part of the animal. 
The teredos form the transition stage between the naked 
acephalas and the bivalves. Their mantle is a kind of fleshy 
