Translations:Adventist Youth Honors Answer Book/Nature/Shells/3/en

a. Mantle

The mantle is an organ covering the soft parts of a mollusk. It secrets calcium carbonate to create the shell.

b. Foot

The foot is the largest visible portion of a mollusk other than the shell. It is the soft part that protrudes from the shell and touches the surface of whatever the mollusk is crawling on.

c. Teeth

The "teeth" of a mollosk are called radula by scientists. They are more like a jagged tongue than they are like teeth (see the diagram on the right). Mollusks use them to chew food and to scrape algae from rocks.

d. Ribs

Ribs are any raised ridges on the surface of a shell.

e. Valve

A valve is half the shell of a mollusk with a two-part shell. The two valves are joined by a hinge. These mollusks are called bivalves, and include clams, oysters, and mussels.

f. Dorsal border

The dorsal border is the edge of a bivalve's shell where the hinge is located.

g. Apex

The apex is the tip or point of the shell. It is not labeled in our diagram, though it is clearly visible (lower right).

h. Operculum

The operculum is a hard structure situated at the end of the foot, and is used to seal off the entry to the shell. You can think of it as a combination shoe/door.

i. Canal

Many marine gastropods are burrowers, and have soft siphons or tubes that extend from the mantle. Sometimes the shell has a siphonal canal to accommodate this structure. These siphons act as snorkels, enabling the animal to continue to draw in a water current containing oxygen and food into their bodies. The siphons are also used to "taste" the water, in order to detect prey from a distance.