182 ZOOLOGY 



The Solenidse 1 include the "razor-shell" (Fig. 167). 

 This animal, like the shell, is elongated and subcylindrical. 

 By means of its foot, which can be protruded between the 



FIG. 1G7. Enxis directus. Young. Nat. size. Photo, by W. H. C. P. 



\alves, it excavates, with great rapidity, a hole in the sand 

 or mud, into which it draws itself. These mollusks are 

 sometimes used for food, but it is not easy to get them in 

 quantity. 



The Mactridae 2 include species commonly known in the 

 North as hen-clams and surf-clams. They are more ellip- 

 tical and larger than the common hard-shelled clam or " quo- 

 hog," and have a proportionately lighter shell (Fig. 168). 

 They are not often used as food because they become very 

 tough when cooked. 



The Myidae 3 include the common clam of New England, 

 My a arenaria, abundant along our whole Eastern coast and 

 used as food chiefly in New England. These clams occur 

 in great numbers in every mud-flat. Their great siphon is 

 extended at high tide to* the surface of the ground, so as to 

 take in and throw out water (Fig. 169) ; but at low tide it is 

 retracted, and the clam lies invisible in its burrow. This 

 clam was much prized by the Indians, as the great, ancient 

 shell-heaps along the coast testify. In 1892 the clam com- 



, a channel or tube. 2 ndicrpa, a baking-trough. 



3 /AiJa, Greek name for a kind of mussel. 



