HABITS AND MOVEMENTS OF THE RAZOR-SHELL CLAM. 137 



sible to move. Although the machinery for this is rather clumsy, 

 and was primarily designed for another purpose, that of burrow- 

 ing, it might be the deciding factor in the struggle of life. The 

 fact that young specimens may be taken at the surface of the 

 water, even the fact that the animals are able to swim at all, indi- 

 cates that they probably occasionally change their positions. The 

 statement made by Woodward (8) that the animals never volun- 

 tarily leave their burrows seems doubtful. They certainly do 

 leave the mud when they are about to die, and there is no reason 

 to believe that they might not voluntarily move from one place 

 to another should occasion require. 



Leaping may aid the animals in getting free from certain kinds 

 of bottom or even occasionally in escaping enemies, should they 

 be removed from the mud in any manner. Not infrequently 

 specimens that have been swimming might become lodged so 

 they could not burrow without changing their positions, and 

 then the leaping movements would be of advantage. 



SUMMARY. 



The animal is very active, burrows with great rapidity, and 

 may also swim and leap. 



In burrowing, the foot is worked into the mud as it is protruded, 

 the end is then swelled into a knob, and by its sudden withdrawal 

 the shell is drawn to the position of the anchored end of the foot. 

 Simultaneous with the retraction of the foot, a strong jet of water 

 is thrown from the anterior end of the shell, so the mud is soft- 

 ened or even washed away as the shell descends, an action 

 similar to that of some of the modern pile drivers. A collar, 

 formed by the anterior end of the mantle, surrounds the foot 

 and acts as a scraper that prevents mud from being drawn into 

 the shell with the foot. 



The animal is able to swim by throwing jets of water from the 

 anterior end of the shell, thus progressing backward by a series 

 of jerks. 



By the uncommon activity of the foot the animal is able to 

 throw itself about on the bottom. 

 UNIVERSITY OF MAINE, ORONO, MAINE. 



