selves down again. With the next wave the process is 

 repeated. 



In Florida, people collect Donax by the thousand, 

 separating them from the sand with coarse sieves, 

 as the distinctive ingredient for coquina soup. Otii- 

 ers pick through the beach drift for empty shells of 

 this kind and mount them on place cards as "butter- 

 fly shells." They are marked with suffused colors or 

 with radiating bands in purple, pale blue, green, yel- 

 low, tan, and various shades of pink, but hardly any 

 two of them are identical. In some places the accumu- 

 lation of dead coquinas becomes consolidated into a 

 soft limy rock that hardens upon exposure to air. 



The Pacific Ocean, despite its name, tends to be 

 violent on the coast of America. There the surf- 

 dwelling clam Tivela siiiltoniin is known as the Pismo 

 clam. It is a far larger animal with a somewhat tri- 

 angular shell. These clams maintain their position 

 in the sand, always with the hinge toward the open 

 ocean. They appear to use a jet of water from the 



mantle cavity beside the foot to aid themselves in 

 pulling the shell into the sand. 



In spite of the difficulty of collecting Pismo clams 

 in the heavy surf, and the fact that man is their chief 

 enemy, the annual census of this shellfish in Cali- 

 fornia shows that its numbers are shrinking. Even a 

 limit of fifteen 5-inch clams per person per day, plus 

 a ban on all shipments and complete protection in 

 some areas, has not halted the decline. 



On sandy coasts throughout the world, razor clams 

 live just below the surface, sometimes with the pos- 

 terior end of the shell projecting slightly above the 

 flooded beach. Siliqua has a rather short oval shell 

 with a very sharp edge, En.si.s an elongate and almost 

 rectangular shell, slightly curved and suggesting the 

 blade of a straight razor. The foot in each kind is 

 at one end and is extremely agile. With it the clam is 

 expert at digging in quickly if waves wash the sand 

 away. 



At slightly greater depths in beaches where the 



Queen scallops, Chlamys opercularis, swimming about as they escape from a starfish. (Eng- 

 land. D. P. Wilson ) 



189 



