CHAPTER IV 



Fig. 46 



CHAMA, CARDIUM AND VENUS 



We pass now to some en- 

 tirely different shells; very 

 irregular, very rough, and 

 very firmly fixed in their 

 places. A picture of one of 

 these shells is shown in Fig- 

 ure 46. This species is 

 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. Some- 

 times they are white or almost colorless, and some- 

 times they are dashed with rosy red. The inside of 

 the shell is lined with a white, opaque layer, which 

 is beautifully crenulated at the edge. The living 

 shell is always attached to some firm support, like a 

 rock or a j)ost. So strong is the adhesion that you 

 must break off a part of the rock or you will sacri- 

 fice 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 



