Tfi-ble 2 (continued) 



Sometimes clam tracks just like those seen in the laboratory may be found in the field. 

 Their comparative scarcity is probably due to ttieir impermaxience . Since they are very 

 small farrows, end made under water, it would take very little current or rippling to 

 obliterate them. Therefore, they seldom would last until after the tide left the flat, and 

 when they do last that long they probably represent only a fraction of the tracks made 

 during the preceding high tide. Some very clear tracks were seen on a firm sandy flat 

 at Essex in April 1953. These varied in length from 2 or 3 inches up to about 10 inches, 

 and were rather evenly scattered over the flat at a density estimated ac 1 per 25 or 35 

 square feet. By carefully digging with a jackknife blade, a 5- to 8 -mm. clam could 

 always be found precisely at one end or the other of the small f^arrow . 



Thus it seems the small clams have two methods of moving when they come up out of 

 the soil. They may crawl short distances, or they may be carried longer distances by 

 currents . In either case the ciams have some influence on their dispersal, as pointed 

 out by Baptist (1955). He found that the smaller clams (2-13 mm.), which were moved 

 most extensively by the currents, also burrowed more rapidly and in larger numbers per 

 allotted time than did larger clams (14-22 mm.). 



