CONCHIFERA OR BIVALVES. 



121 



last century. The accounts of the pearl fishery 

 are exceedingly interesting. 



Division II. — Ligament not marginal, con- 

 tracted into a short space under the bosses. 

 Always visible. The shells are all inequivalve. 



Two families, Pectenidce, Ostreidce. 



Family 4. — Pectenidce. * 



The genera of this family are all more or 

 less fan-shaped, and marked with rays from the 

 bosses to the circumference ; the substance of 

 the shell is solid, not foliaceous. Some are 

 attached, others free. — There are five genera. 



77. Pedum. — Shell irregular, longitudinal, 



* Les Pectinides, Lamarck. 



