I2O 



Descriptive Zoology. 



in mind Venus mercenaria, which, farther north, and away 

 from the coast, would be designated as the " hard clam," 

 "round clam," or "quahog." Both are frequently found 

 in the markets inland. 



The Soft-shell Clam. This clam 

 lives in a vertical burrow with the 

 anterior end down. Instead of 

 having short siphons like the fresh- 

 water clam, the posterior margins 

 of the mantle lobes are extended 

 and* grown together to form a long 

 double tube, which reaches to the 

 surface of the sand or mud, the body 

 being sometimes a foot from the 

 surface. The two mantle lobes are 

 united along their entire edges, 

 except at the two siphon apertures 

 and an anterior opening, for the 

 projection of the foot. The ventral 

 channel is the incurrent and the 

 smaller dorsal one the excurrent. 

 As in the clam we have studied, 

 the incurrent siphon has a fringed 

 margin and is very sensitive. The 

 border is also dark colored, so that 

 it is not readily seen, and if disturbed 

 it is withdrawn into the hole. At 

 low tide the tube is generally so re- 

 tracted. At this time clams are 

 hunted and dug up. 



As the clam grows, it deepens and 

 widens its burrow. The foot is small, and the old clam, dug 

 up and left on the surface, has difficulty in making a new 



FIG ' 74 



The arrows show the currents in 

 the siphons. 



From Kingsley's Zoology. 



