CHAPTER III 
OYSTERS AND SMALL CLAMS 
The shell shown in 
Figure 24 is found 
along the whole coast. 
Its name is Monia mac- 
roschisma, Desh., the 
Pearly Monia. It is also 
known as Placuanomia 
and Pododesmus. It be- 
longs very closely to 
the oyster family, but 
has decided differences. 
You will notice that one 
of the valves is much smaller than the other, and 
that it also has a large hole in the center, through 
which you can see an oval muscle-sear with lines 
radiating from the center. The small valve is 
rarely found, as it usually adheres to the rock, 
even after the death of the animal, while the up- 
per valve is torn off by the waves and washed 
ashore. The outside of this upper valve is rough, 
and marked by irregular, radiating ridges; but 
the inside is sometimes beautifully pearly, the 
green and purple tints being most common. There 
are two muscle-sears, the lower one of which is 
not shown in the cut, but it is smaller and smoother 
than the other. The shell is normally circular, 
