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PANDORIDAE 469
ally compressed. Outer surface whitish (opalescent when worn), commonly
with numerous, weak, radial, dark lines of periostracum. Interior glossy and
with an opalescent sheen. Ossicle inside, under hinge, is opaque-white. Very
similar to our figure of the Atlantic hyalijja. Common in sandy mud bot-
toms of many California sloughs and bays down to 40 fathoms.
Genus Entodesma Philippi 1845
Subgenus Agriodesma Dall 1909
EntodesTfia saxicola Baird Northwest Ugly Clam
Plate 29m
Alaska to San Pedro, Cahfornia.
2 to 5 inches in length. A very peculiar, ugly and misshapen clam found
along the shore burrowing into rocks. Generally oblong in shape, with the
posterior end flaring and gaping. Covered with a thick, rough, brown peri-
ostracum which partially flakes oflF when dry. Interior brownish tan to
whitish with a slight opalescence. Hinge \\'ithout teeth, but with a rather
large, oblong, whitish ossicle lying under the internally placed ligament.
Moderately common from Washington to southwest Alaska.
Genus Mytilimeria Conrad 1837
A peculiar, bladder-shaped, very thin shell found embedded in compound
ascidians or sea squirts.
Mytilhjieria Jiuttalli Conrad Nuttall's Bladder Clam
Alaska to Lower California.
Plate 29q
I to 2 inches in length, obliquely oval, inflated, very fragile, opaque
with a thin, brownish periostracum. Beaks small and spiral. No teeth in the
weak hinge, but a small, calcareous ossicle is present. Color white with
underlayers of slightly pearly material. Common under rocks at low tide to
10 fathoms, always embedded in compound ascidians or sea squirts.
Fa7?nly PANDORIDAE
Genus Pandora Chemnitz 1795 (Opinion 184)
Pandora trilineata Say Say's Pandora
Cape Hatteras, N®rth Carolina, to Florida and Texas.
Figure 96b
% to I inch in length, almost half as high; half-moon-shaped in outline,
and with a strong, squarish ridge along the hinge margin which extends pos-
teriorly into a fairly long rostrum. Valves very flat, the entire shell very