312 



Gih?ia72 A. Drew 



known to occur at moderate depths. Dr. K. Kishinouye writes 

 me that the Japanese "fishermen catch razor-shell clams from the 

 bottom of the sea, ten or more fathoms in depth, by means of 

 slender spears that are weighted at their upper ends and held at 

 the end of a rope." Inasmuch as the catch is made by simply 

 pulUng up and dropping the spear and is dependent upon acci- 

 dentally striking the clams, they must be fairly abundant to make 

 such a method profitable. The animal fives embedded in the 

 mud almost perpendicularly, with the siphon end usually barely 

 protruding above the surface. Occasionally specimens are found, 

 when the mud-flat is bare, with half or more of their shells exposed, 

 but, judging from observations of specimens in aquaria and of 

 other specimens in their native mud-flats that had not been dis- 

 turbed and were covered with water, I am inclined to believe that 

 this is not a usual position, and is probably assumed as the result 

 of the stimulation of the heat of the sun. 



When an animal is disturbed, as by jarring the mud or by 

 stimulating the exposed siphons, it almost instantly disappears 

 into the mud. This is evidently its means of escape from enemies. 

 The burrowing is done by means of a remarkably long, active, 

 cyfindrical foot. Figs, i and 2, /, that can be protruded from the 

 anterior end of the shell to a distance equal to more than one-half 

 of the length of the shell. When fully extended the end of the 

 foot is swelled to form a knob that serves as an anchor for the 

 animal to draw itself into the mud. The fact that the animal 

 disappears so promptly after it is disturbed indicates that the foot 

 is probably kept somewhat extended when the animal is at rest 

 in its usual position. 



The margins of the mantle lobes are fused together so that four 

 openings into the mantle chamber are left. Two of these are the 

 openings of the siphons. Fig. i, hs and ^.r, the third is the opening 

 through which the foot is protruded, and the fourth is a small 

 opening about midway on the ventral margin. Fig. i, vo. What 

 function is performed by the last mentioned opening is not clear. 

 With an expanded animal in a dish of sea-water it is easy to demon- 

 strate that a current of water enters this opening. This is to be 

 expected as the opening leads into the branchial chamber, into 



