The form of the shell is orbicular and equivalve, without the elongated
transverse base on the cardinal tooth, and the sloping sides of the
opening for the passage of the byssus are perceptible on both valves;
these peculiarities distinguish it from the Avicula.
Shell sub-equivalve, rotundate, nearly square, externally squamose; the
inferior cardinal margin straight, not caudate anteriorly; a sinus at
the posterior base of the valves for the passage of the byssus; the left
valve being at this place narrow and channelled; hinge linear, without
teeth.
Meleagrina margaritifera.
Meleagrina albina.
_M. margaritifera._ The pearl-bearing Meleagrina, sometimes called the
mother-of-pearl oyster.
Species slightly oblique, somewhat square, pearly, very thick,
compressed; undulated and transversely striated, with a series of
lamellated longitudinal scales; exterior greenish, interior pearly. This
shell is celebrated for its irridescent colours, and is valued for the
beautiful and costly pearls it produces. These pearls are formed from a
deposition of the substance destined to line the shell upon sand or
other bodies, casually or purposely introduced within the mantle of the
animal; the shell itself is the mother-of-pearl used for inlaying, or
making various elegant trinkets.
FAMILY XVIII.
PECTINIDES. Seven genera.