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462 American Seash ells
2 to 2^4 inches in length, very elongate, moderately gaping at the bluntly
rounded, posterior end, and widely gaping at the foot end. Top margin
of shell folded back on itself at, and just anterior to, the beaks. No distinct
radial groove on the sides of the valves. Sculpture at anterior end is of prickly,
concentric lamellae which fade out toward the smoothish posterior third.
Siphon covered with a heavy, brown periostracum. May be dug out of
very soft shale at very low tides in a few localities. Moderately common.
Miss Turner advises me that this species must take the earlier name of Barnea
spathidata Deshayes. It was formerly known as B. pacifica Stearns.
Genus Zirfaea Gray 1842
Zirfaea crispata Linne Great Piddock
Newfoundland to New Jersey. Europe.
Figure 94c
1 to 2 inches in length, about half as high. Gaping at both ends. Charac-
terized by the radial, indented line which divides the valves into 2 areas: the
posterior section which has coarse, irregular growth lines, and the anterior
section which has fimbriated or scaled growth lines and a serrated edge.
A4oderately common in cold water where it burrows into soft r^ck. This is
the only member of the genus on the Atlantic Coast.
Zirfaea pilsbryi Lowe Pacific Rough Piddock
Bering Sea to San Diego, California.
2 to 4 inches in length, gaping at both ends. Purportedly there are no
accessory plates present, except for a small mesoplax. The folded-back dorsal
margin at, and in front of, the beaks is covered with a thin, periostracal
membrane in fresh material. The yellowish periostracum at the posterior
end (siphonal end) is thin, but is not leaf-like as in Parapholas. No eggshell-
like material over the anterior foot gape. This species appears in old books
as gabbi Tryon. Dead specimens are commonly washed ashore. Siphon
studded with tiny, rounded flecks of chitinous material.
Genus Pholas Linne 1758
Pholas ca77ipechiensis Gmelin Campeche Angel AVing
North Carolina to the Gulf States and Central America.
Plate 32t
3 to 4 inches in length, Mj as high, fragile, purc-\\iiite and closely resembling
the False Angel Wing, Petricola pholadijonms, but lacking a
toothed hinge and ligament, and having a glossy plate rolled over the beaks