or molluscs. The Pearl-bearers of the sea are commonly known as " Pearl
oysters," though they present but little resemblance to our " native
oyster." Indeed although popularly so called they are not oysters in
the scientific acceptation of the word, but belong rather to the group
of sea-mussels. The term, however, is so commonly employed and
universally recognised, that it would be pedantry to abandon it or to
attempt to introduce any other word as a substitute.
For our purpose the Pearl-bearing molluscs may be conveniently divided into two great groups, viz.—
I. The Marine.
II. The Fresh-water.
Pearls, whether marine or fluviatile, are produced by organisms
belonging to that great group of bivalve shell-fish which was termed by
the famous French naturalist, Lamarck, the Conchifera. This
name however is by no means well-chosen, inasmuch as it literally means
"Shell-bearers" and might therefore with equal propriety be bestowed
upon other molluscs that secrete shells, such as certain cephalopods and gasteropods. It has hence become usual to replace the old term Conchifera by the better chosen name Lamellibranchiata,