HABITS AND MOVEMENTS OF THE RAZOR-SHELL CLAM. 129 



remain quiet until disturbed again, or it will immediately vanish 

 beneath the surface of the mud. If a specimen is grasped and 

 pulled upward there is an immediate response that is so power- 

 ful that the animal frequently escapes and disappears. This fact 

 Tryon (6) mentions, saying : " It may often be seen at low tide 

 projecting a little above the level of the sand but, if touched or 

 disturbed, it descends with astonishing rapidity and force, much 

 to the amazement of him who may lay hold of it thinking to 

 make an easy capture." These observations indicate that the 

 animal probably habitually keeps its foot protruded some distance 

 out of the shell to be ready for disturbances. 



Specimens taken in firm sandy soil, where the depth can be 

 noted, are frequently found several inches below the surface. 

 Verrill and Smith (7) report that this species digs somewhat 

 permanent burrows that extend nearly perpendicularly into 

 the sand to the depth of three feet, and Woodward (8) states 

 that the animals never voluntarily leave their burrows. I have 

 never been able to demonstrate permanent burrows in the locali- 

 ties where I have worked, but the usual muddy character of the 

 bottom was not satisfactory for the purpose. I doubt, however, 

 if such burrows are habitually constructed. The character of the 

 bottom where they live is frequently not suitable for permanent 

 burrows unless something like a tough secretion is added to the 

 mud to keep it in place, and such a secretion does not seem to be 

 formed. Specimens in aquaria never seem to construct anything 

 like permanent burrows. 



As individuals are known to burrow to some depth it is prob- 

 able that in digging for them, those in the immediate vicinity are 

 disturbed and burrow beneath the reach of the shovel. Verrill 

 and Smith (7) call attention to how easily disturbed they are and 

 say : " When thus alarmed it is generally useless to try to dig 

 them out, for they quickly descend beyond the reach of the 

 spade." Dr. J. Gwynn Jeffreys as quoted by Tryon (6) reports 

 them as having exceptional powers for detecting disturbances. 

 He says : " They are evidently sensible to vibratory movements 

 in the air, as well as on ground, taking alarm at greater or less 

 distances according to the state of the atmosphere and the direc- 

 tion of the wind." It is hard to verify these observations and I 

 am inclined to think they are not accurate, but there can be no 



