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MOPALIIDAE 315
Family MOPALIIDAE
Genus Mopalia Gray 1847
Mopalia ciliata Sowerby Hairy Mopalia
Alaska to Monterey, California.
I to 1% inches in length, oblong, usually colored with splotches of
black and emerald-green, although sometimes having cream-orange bands
on the sides of the valves. Sometimes grayish green with grayish black or
white mottlings. Girdle colored yellowish brown to blackish brown. Valves
slightly beaked; lateral area separated from the central area by a prominent,
raised row of beads. Central areas with many coarse, wavy, longitudinal
riblets, which are sometimes pitted between. Lateral areas coarsely granu-
lated or wrinkled. Posterior valve small, with a deep slit on each side and
a broad, deep notch at the very posterior end. Girdle fairly wide, generally
notched at the posterior end and clothed with curly, strap-like brown hairs
between which are much smaller, glassy white hairs or spicules. Interior
of valves greenish white. Anterior valve granulated and with 8 to 9 coarse,
raised rays of beads. A common intertidal species. The subspecies ivosnes-
senski Middendorff (Alaska to Puget Sound) is supposed to be without the
tiny white spicules in the girdle.
Mopalia muscosa Gould Mossy Mopalia
Alaska to Lower California.
I to 2 inches in length, oblong to oval. Very similar to M. ciliata, but
differing in having a very shallow and small notch at the very posterior
end. Color usually a dull-brown, blackish olive or grayish. Interior of
valves blue-green, rarely stained with pinkish. Girdle with stiff hairs resembling
a fringe of moss. The following species have been considered by some
workers as varieties of 7miscosa, and perhaps with some justification: lignosa
Gould, hindsi Reeve, acuta Carpenter, the latter having also been named
plumosa and fissa by Carpenter. A common intertidal species.
Mopalia lignosa Gould Woody Mopalia
Alaska to Lower California.
I to 2^4 inches in length, oblong. Color a grayish green or blackish
green, rarely with whitish cream and brown, feathery markings. The sculp-
turing on the valves is very delicate and may consist only of numerous small
pittings near the center. Concentric growth lines in smoother specimens are
quite easily seen. Radial ribs absent on the end valves. Girdle solid or macu-