The Club Shells

Genus CLAVIGELLA, Lam.

SHELL with right valve free, left imbedded in tube; tube cylindrical, frilled above, base bordered with tubuli; mantle frilled, with tentacular processes. Six living and fourteen fossil species. Mediterranean Sea to Australia and Pacific Islands.

The Little Club Shell (C. aperta, Sby.) has a much larger shell than the watering-pots. The valves seem external at the base of the club-shaped tube, though one is solidly fastened to it. Instead of full frills, numerous flaring rims mark periods of cessation of growth. After the valve becomes fixed, the animal ceases to burrow and secretes a strong flaring border to the tube. Sediment is deposited gradually about the valves, and the mollusk's method of overcoming this trouble is to build another story to his chimney, and again another as the deposit increases. Length of tube, 3 inches.

Habitat.-Mediterranean Sea.