download pdf

SOLEMYACIDAE 33 3
Order PALAEOCONCHA
Family SOLEMYACIDAE
Genus Solemya Lamarck 1818
The Awning Clams are very primitive in their characters and they have
no near relatives. Their shells are fragile, with a weak, toothless hinge,
gaping at both ends, and covered by a polished, horny, brown periostracum
which extends well beyond the margins of the valves.
Subgenus Petrasma Dall 1908
Solemya velum Say Common Atlantic Awning Clam
Nova Scotia to Florida.
Plate 27a
% to I inch in length, very fragile, and with a delicate, shiny, brown
periostracum covering the entire shell and extending beyond the edges. Light
radial bands of yellowish brown are present in some specimens. Chondro-
phore supported by 2 curved arms. Commonly dredged in shallow water in
mud bottom. Compare Florida specimens with occidentalis.
Solemya borealls Totten Boreal Awning Clam
Nova Scotia to Connecticut.
2 to 3 inches in length, very similar to velum, but more compressed,
heavier, and colored grayish blue or lead on the inside of the valves (instead
of purplish white). The striking difference is in the siphonal opening of the
animal. In velum, there are 2 small, median, low tubercles above the opening
and 5 or 6 pairs of short tentacles at the lower end of the opening. In bo-
realis, there are 3 pairs (one of which is large and long) of tentacles above
the opening and about 1 5 smaller ones bordering the lower half. S. borealis
is moderately common offshore.
Solemya occidentalis Deshayes West Indian Awning Clam
West coast of Florida and the West Indies.
^ inch in length, similar to S. velum, but much smaller, and has only
one slender ridge or rib bordering the chondrophore. Uncommon just off-
shore. Described first by Deshayes in 1857, later by Fischer in 1858.
Solemya valvidus Carpenter Pacific Awning Clam
San Pedro, California, to the Gulf of California.