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Rh 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 Plate 27a Nova Scotia to Florida. % 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 bore alls 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.