The valves of this genus greatly resemble those of the common oyster,
but have ears, and are covered with long recurved or straight-pointed
spines.
The lower valve is much larger than the upper, and has foliaceous
laminæ, by which it is attached to the other substances. They are found
in all seas of hot countries, but particularly in the Indian; they
adhere to rocks, coral, &c., oftentimes in large groups.
The usual colours are red, purple, white, brown, or orange, several of
which are sometimes blended in the same shell.
Shell solid, adhering, sub-regular, more or less spined,
sub-auriculated, inequivalve; the right or inferior valve fixed, much
more excavated than the other, and having behind, at the summit, a
triangular face, which enlarges and elongates with age; hinge
longitudinal, provided in each valve with two strong teeth entering into
corresponding cavities; ligament short, almost medial, partly exterior;
one sub-dorsal, muscular impression.
Spondylus gædaropus.
S. Americanus.
S. arachnoides.
S. candidus.
S. multilamellatus.
S. coccineus.
S. crassisquama.
S. spathuliferus.
S. ducalis.
S. longitudinalis.
S. costatus.
S. variegatus.
S. longispineus.
S. regius.
S. avicularis.
S. microlepos.
S. croceus.
S. aurantius.
S. radians.
S. zonalis.
S. violacescens.
_S. gædaropus._ The thorny red Spondylus. Pl. 15, fig. 1.
Upper valve red, under one white, with longitudinal striæ or ribs; rough
granulations, and somewhat tongue-shaped; rather short truncated spines.
_S. longispineus._ The long-spined Spondylus.
Thickly spined, longitudinally sulcated and ribbed; alternate spines
arcuated and tongue-shaped; valves of a reddish colour; umbones orange.