100 
CAPE COD. 
rid of. Sponges, which are picked up on the shore, as is 
well known, retain some of the sand of the beach to the 
latest day, in spite of every effort to extract it. 
I found one stone on the top of the bank, of a dark 
gray color, shaped exactly like a giant clam {Mactra 
soUdissima), and of the same size; and, what was more 
remarkable, one half of the outside had shelled off and 
lay near it, of the same form and depth with one of the 
valves of this clam, while the other half was loose, leav¬ 
ing a sohd core of a darker color within it. I afterward 
saw a stone resembling a razor clam, but it was a solid 
one. It appeared as if the stone, in the process of for¬ 
mation, had filled the mould which a clam-shell furnished; 
or the same law that shaped the clam had made a clam 
of stone. Dead clams, with shells full of sand, are 
called sand clams. There were many of the large clam¬ 
shells filled with sand; and sometimes one valve was 
separately filled exactly even, as if it had been heaped 
and then scraped. Even among the many small stones 
on the top of the bank, I found one arrow-head. 
Beside the giant clam and barnacles, we found on the 
shore a small clam {Mesodesma arctatd), which I dug 
with my hands in numbers on the bars, and which is 
sometimes eaten by the inhabitants, in the absence of the 
Mya arenaria, on this side. Most of their empty shells 
had been perforated by some foe. — Also, the 
Astarte castanea. 
The Edible Mussel {Mytilus eduUs) on the few rocks, 
and washed up in curious bunches of forty or fifty, held 
together by its rope-like hyssus. 
The Scollop Shell {Pecten concentricm')^ used for 
card-racks and pin-cushions. 
Cockles, or Cuckoos {Natica her os), and their re- 
