CHAPTER IV 
CHAMA, CARDIUM AND VENUS 
We pass now to some 
very different shells; very 
irregular, very rough, and 
very firmly fixed in their 
places. <A picture of one 
of these shells is shown in 
Figure 46. This species 
named Chama pellucida, 
Sby., the Agate Chama. 
You notice by the figure 
that the inside of the shell 
is smooth enough, and that there is a big, oblique 
hinge-tooth near the upper right-hand corner. The 
outside, however, is very rough, being covered by 
many close frills, which are translucent, like agate 
or chalcedony. Sometimes these are white or 
almost colorless, and sometimes they are dashed 
with rosy red. The inside of the shell is lined with 
a white, opaque layer, which is beautifully crenu- 
lated at the edge. The living shell is always 
attached to some firm support, like a rock or a post. 
So strong is the adhesion that you must break off 
a part of the rock or you will sacrifice a part of 
the shell. It is very easy to overlook them, as they 
appear like ragged knobs on the rock, but when 
you have collected a good specimen you will greatly 
admire its peculiar beauty. Upper valves are 
