23S 



ZOOLOGY 



take in and throw out water (Fig. 221) ; but at low tide it is 

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



Fig. 220. — Mactra solidissima, the Eastern hen clam. Nat. size. From 

 Gould-Binney. 



clam was much prized bj^ the Indians, as the great, ancient 

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



FiG. 221. — The "soft-shelled" clani {Mya arenaria), with its siphon ex- 

 truded to the right and its foot projecting to the left. 



merce for New England was estimated to be worth nearly 

 half a milhon dollars (Fig. 222). 



The hard-shelled clams (Veneridse ^) include Venus merce- 



' Venus, the goddess of love. 



