The Watcring-pot Shells and Club Shells 



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 mol- 

 lusk'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. . 



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