CHAPTER VII: THE SOFT-SHELL CLAMS. 

 SAND CLAMS 



Family MyidjB 



Shell strong, opaque, unequal, gaping; cartilage process 

 flattened on left valve; ligament internal; epidermis wrinkled; 

 mantle edges united except at pedal aperture; foot small; siphons 

 long, united, retractile; gills two on each side, elongated. 



Genus MYA, Linn. 



Shell oblong, thin, soft, chalky; left valve smaller; gape at 

 both ends; palHal sinus large; foot tongue-like; palpi free. Three 

 living species; seventeen fossil in United States and Europe. 



The Soft-shell Clam (M. arenaria, Linn.) is found on 

 gravelly mud flats of river mouths from South Carolina to Green- 

 land and Great Britain; by colonisation it has become estab- 

 lished in San Francisco Bay. Its normal station is between high 

 and low tide marks. Even rocky shores may harbour it, the 

 mollusk burrowing in the sediment deposited in crevices. The 

 animal lies head downward, its siphon tube extending upward into 

 the water, if the tide is in ; in any case, to the surface of the sand, 

 or mud, to get a supply of food and oxygen. The limit of depth 

 reached is about one foot. 



Walk over the territory of the sand clam, at low tide, and 

 little vertical spurts of water show where the siphons have been 

 suddenly drawn down as a measure of safety. The length of 

 the siphon exceeds that of the shell, which is as big as the palm 

 of your hand. The mantle is prolonged into a tough protective 

 sac to the fringed tips of the united siphons. A small hole at the 

 opposite end gives egress to the pointed foot, the organ by which 

 the mollusk travels through sand and mud. 



Inferior to the quahog in popularity, the sand clam is, never- 

 theless, an important food mollusk. Up and down the Atlantic 

 coast, in San Francisco and in British coast towns, the demand 



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