472 American Seashells 



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 



