Separated from the Spondylus of Linnæus on account of its distinct
structure. The ligament is altogether internal; it is without ears, and
the prolonged beak so conspicuous in that genus. The Plicatula has the
faculty of affixing itself to another body, so that many are found
grouped together in clusters. The valves are strongly plaited within and
without, closely interlocking with each other.
Shell solid, adhering, sub-irregular, without ears, inequivalve, pointed
at the summit, rounded and plaited behind; hinge with two strong teeth
in each valve, with a cavity between them, in which the ligament is
internally inserted.
Plicatula ramosa.
P. depressa.
P. cristata.
P. reniformis.
P. Australis.
_P. ramosa._ The branched Plicatula. Pl. 15, fig. 2.
Oblong, trigonal, very thick; strong longitudinal plaits; exterior
brown, with a yellow tinge, with reddish arrow-shaped markings; interior
white.