142 



FIRST LESSONS IN ZOOLOGY 



clambake, is found in all the northern seas of the world. 

 . . . All along the coasts of the eastern States every 

 sandy shore, every mud flat, is full of them, and from 

 every village and hamlet the clam-digger goes forth at 

 low tide to dig these esculent bivalves. The clams live 

 in deep burrows in the firm mud or sand, the shells some- 

 times beintr a foot or fifteen inches below the surface. 



Fli.. 105, — A gnjup uf marine Pacific Coa^t molluscs; in upper left-hand 

 corner, Purpura saxicola; next to the rijjht, Littorina scutulata; farthest 

 to ri<;ht, limpets. Afmara spi-(irnm; left-hand lower corner, Mylilus 

 inhforjiiniuis; in riudil-hand lou-er corner the black shells just alwve 

 the larLje clam-shell. C lihiriislniiiiiiii fuiu-bral,:. (Natural size; from 

 livmi^ specimens in a tide-po(j| on the Hay of ^hjnterey, California.) 



When the flats are covered with water his clamship ex- 

 tends his long siphon uj) through the burrow to the surface 

 of the sand, and through one of these tubes the water 

 and its m)'riads of animalcules is drawn down into the 

 shell, furnishing the gills with o.x_\'gen and the mouth 

 \\itli food, and then tlic \\;iter charged with carbonic 

 acid and reftise is forced out of tlie other siphon. When 

 the tide ebbs the siphons arc closed and parti)- with- 

 drawn. 



