24 



vertical cylindrical cavity, about an inch and a half 

 in diameter, and a foot or more in depth. The mo- 

 ment the animal is surprised, it descends rapidly to 

 the bottom of its cell, protruding and expanding the 

 inferior part of its body into a button-like extremity, 

 which renders it difficult to withdraw the shell until 

 the sand is excavated entirely around it. 



^^This species is also abundant on the main land at 

 Great Egg Harbour, about half a mile south of the 

 Point-house; but the coast is here muddy, and the 

 shells more or less decorticated, while those on the 

 bar already mentioned have a beautiful, unbroken, 

 straw-coloured epidermis. 



*^^The Solen ensis and My a arenaria are met with 

 it the same beds." 



Mr. I. Lea informs me that this species is abund- 

 ant at Cape May, on the same coast ; and he mentions 

 as a remarkable circumstance, that in one instance 

 when the retreat of the animal had been suddenly 

 cut off, it darted a foot or more above the surface of 

 the sand. 



North of New Jersey this shell is very rare ; but 

 it is common at the mouths of rivers on every other 

 part of our coast. 



