RAZOR SHELLS. 285 
extremities are so different from the forms of all 
other shells, that even the unscientific observer 
regards them with curiosity and interest. The 
resemblance which the valves bear to the handle 
(scales) of a razor 1s obvious, especially in such 
species as are slightly curved. The valves are 
thin and brittle, covered with an olive epidermis 
which readily peels off. Beneath this the surface 
is marked with strie recording the progress of 
growth, which, following courses parallel to all of 
the margins, impart a singular and peculiar aspect 
to these shells. 
The animals have the mantle united for a por- 
tion of its edges, but allowing the protrusion of an 
enormous foot, which is thick, long, and somewhat 
club-shaped at the extremity. The siphons are 
short, united more or less completely, and fringed 
at the tips. 
The species of this genus, which are not nume- 
rous, live in sandy beaches near the verge of low- 
water, or buried in the soil at greater depths. 
They are most powerful and skilful burrowers, 
often lying buried in a vertical position two feet 
deep, though their ordinary habit is to go only so 
low in the sand or mud, as to allow the extremities 
of the siphons just to reach the top. “ They may 
be said to have regular burrows. When the animal 
is undisturbed, and the tide is in, it lies with the 
tubes at the entrance of its perpendicular hole. 
If it be disturbed, down it goes. In short, its life 
is spent in descending to the depths of its burrow, 
and ascending from it again, by means of the ex- 
tension and contraction of its great muscular foot, 
which is situated at that part of the shell which is 
lowest.” 
