At this point George interrupted Professor Parker by asking him 

 if a certain family of shells in the same case were oysters. Their shells 

 were very irregular, and were attached to each other and to various 

 objects in the same manner as the familiar edible bivalve. "No," 

 answered the Professor, " these are not oysters, although they some- 

 what resemble them. They are members of the family Chamidce, 

 which live in the vicinity of coral reefs in the tropical seas of many 

 parts of the world, and are attached by either valve to some object. 

 Their shells are variously sculptured, some being ribbed, while others 

 are foliated or spinose. In color they vary from pure white, through 

 pinkish, to yellow. A California species, Chama pellucida, is some- 

 times rosy red in color, and a perfect specimen is translucent like the 

 mineral chalcedony. It receives the name of pellucida from its trans- 

 parency. The Chamas of Florida are very handsome shells, Chama arci- 



nella being covered with straight spines, while 

 Chama mawophylla is beautifully frilled. The 

 name of the genus was first given to it by the 

 naturalist Pliny and revived by Linnaeus." 



Placed near the Chama family was a collection 

 of the fresh-water shells belonging to the genera 

 Chi arcinella a &ph<zrium and Pisidiwn, the latter being so small 

 common Florida bi- that we could scarcely see them. Near these we 



Veil V6. (Try on.) 



saw several species of the Cijrenas, which live in 

 the brackish waters of warm countries, buried in the mud. 



"This family," continued Professor Parker, pointing to a group 

 of shells with brilliantly polished surfaces, " comprises the wedge-shells, 

 or Donax. On the shores of Florida and California they may be found 



by thousands buried an inch or two beneath 

 the surface of the sand. The foot is large 

 and pointed, and particularly adapted for 

 burrowing. 



" I am sure you will be interested in the 

 chicken, or hen- clams (Mactra) of which 

 a number of species may be seen in this 

 case. This is a large family, which is repre- 

 sented in all parts of the world, and em- 



Spisuia soiidissima, a common braces some one hundred and fifty or more 



species. On the Atlantic coast of the United 

 States, a species called Spisida soiidissima 

 attains a length of about six inches. They bury themselves just beneath 

 the surface of sandy shores. The long, finger-like foot is used for leap- 



78 



hen - clam of the Atlantic coast 

 of the United States. (Tryon.) 



