OTHER BIVALVE MOLLUSKS 83 
are largely made up of old shells, ashes, and char- 
coal dust. This shows that the Indians had their 
fires there, and that they threw away the rubbish 
which was left from their meals, and then returned 
to repeat the operation on the slowly rising pile. 
It is interesting to examine the shells of these 
old heaps, and thus see what species formerly 
abounded on the adjacent mud-flats. I have found 
various kinds of 
shells, but by far 
the most abundant 
ones are those of 
the species named 
Macoma nasuta, 
Conr., the Bent- 
nosed Macoma, 
Figure74. Al- 
though so abundant 
then, this species seems to be dying out, and its 
place is being rapidly occupied by the introduced 
Rhode Island clam, Mya arenaria, which we will 
presently consider, but not a specimen of that shell 
is found in the mounds. Macoma nasuta is a com- 
mon species on the coast, reaching from Kam- 
chatka to Mexico. It inhabits muddy flats, bur- 
rowing quite deeply, and reaching the water by 
two small, red siphons. The shell is smooth, flat 
and thin; rounded in front, but narrowed and bent 
to one side behind. The hinge-teeth are small, and 
im one valve the pallial sinus reaches to the for- 
ward muscle-sear. Its color is white, and the com- 
mon length is two inches. 
Fig. 74 
