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Pisiiio clam is most at home, the sand is piled up in offshore bars lying 

 below ordinary low tide, though perhaps bared at extreme low ebbs, 

 and usually separated from the exposed beach by channels varying 

 from two or three to a dozen feet deep. These bars are relatively 

 transient, some lasting for several months, while others may last but 

 a single tide, being formed and scattered with amazing rapidity, if 

 the waves and tides occur in the correct sequence. How destructive 

 such changes may be, is seen in some winters when the heavy cutting 

 surf washes out and rolls up the beach such numbers of the clams that 

 windrows are found at high tide line. This occurred, for instance, in 

 December, 1915. 'That the constant shifting of the apparently monoto- 

 nous sands is not always fatal to this clam in spite of its stout shell 

 is due to its constant activity. When new bars form and rise, the 

 animals are found at the surface. When the bar is swept out it is 

 seldom that more than a stray individual washes up and this can only 

 mean that the clam is constantly and actively burrowing up or down 

 to escape being buried too deeply to reach its supply of water or to 

 avoid being completely dislodged and thrown to the mercy of the surf. 



For this activity its large muscular foot with its thin knifelike edge 

 is well fitted though its heavy shell is less readily drawn through the 

 sand than is that of its neighbor on these l)eaches, the razor clam. 

 Small individuals up to 30 or 40 mm. (1|- inches) bury themselves 

 readily if thrown out on the firm wet sand just above the wash of the 

 waves. Some watched on Oeeano Beach were covered in 30 to 45 

 seconds. Adults find this more difficult but will bury themselves if 

 they are covered with water and can get time between the waves which 

 sweep them up and down the beach, to get a "foothold." 



Another delicate adaptation is found in the siphons. These, as 

 already stated, are short, a condition found in most actively Inirrowing 

 forms. The exhalent tube is somewhat the shorter and its delicate, thin 

 walled tip, rimmed with a few short tentacles, closes in a line parallel 

 with the margins of the shell when no current is passing out. At other 

 times, the current of water will prevent the entrance of sand. The 

 inhalent siphon is somewhat enlarged at the tip and ends in a broad 

 fiat surface that to the first glance shows no opening. If one has the 

 patience to examine this surface with a low power lens as the animal 

 lies at rest in some little pool, it will be seen that the aperture is 

 closed by a delicate system of branched tentacles so closely placed that 

 while every sand grain dropped upon them is securely supported the 

 water has free access to the mantle cavity through this living screen. 

 As the water flowing over them nearly always contains some sand and 

 at times is filled with whirling clouds of it, the value of this arrange- 

 ment is obvious, since the supply of water bears both oxygen and food 

 to the clam. 



It was noted l)y Thompson* that the razor clam is found with the 

 hinge toward the open ocean and he has suggested that this position 

 bears some relation to the question of water supply to and from the 

 siphons. The question of position was carefully studied in the Pismo 

 clam and the same condition was found, the hinge being almost invari- 



*Report on the Shellfish of British Columbia, Report of the B. C. Commissioner of 

 Fisheries, 1913, p. R 108. 



