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472 Thracia curta Conrad Short Western Thracia Alaska to Lower California. I to 1% inches in length, very similar to trapezoides, but suboval and lacking the prominence of rostration. It is very close in shape to our illus- tration of the Atlantic T. comadi. A moderately common species. John Q. Burch reports that it is relatively abundant at San Onofre, California, in the rubbly reef at extreme low tides. It has also been taken from wharf pilings, and it is commonly dredged in over 20 fathoms on shale bottoms. Genus Cyathodonta Conrad Similar to Thracia, but the right beak is without a round hole, and the ligament is internal on a definite chondrophore, and the valves are with oblique, concentric undulations. This is sometimes considered a subgenus of Thracia, not without justification. There is only one species on the Pacific Coast of America. Cyathodonta undulata Conrad Wavy Pacific Thracia Plate 3 IS Monterey, California, to Tres Marias Islands, Mexico. 1/4 inches in length, subovate, very thin and fragile, white, and with obliquely concentric undulation which are largest at the anterior end, but disappear toward the posterior end of the shell. Minute, crowded, granu- lated, radial lines are also present. Uncommon. C. diibiosa Dall and C. pedroana Dall appear to be this species. Family PERIPLOMATIDAE Genus Feriploma Schumacher 18 17 Shell small, oval, right valve fatter than the left, with a slight pearly sheen, hinge with a narrow, oblique spoon and a small, free, triangular litho- desma; ligament absent; anterior muscle scar long and narrow, the posterior one small and ovate. Feriplovia papyratiwn Say Paper Spoon Clam Plate 28W Labrador to Rhode Island. % to I inch in length, oval, moderately compressed, thin-shelled, and dull-white with a thin, yellowish-gray periostracum. Beaks slit or broken by a short, radial break. Spoon-like chondrophore faces downward and is rein- forced by a sharp, curved rib which runs to the inner surface of the valve