Page:American Seashells (1954).djvu/548

Genus Schizothaerus Conrad 1853 Shell large with a roundish posterior gape. Hinge with small cardinal teeth; lateral teeth very small and close to the cardinals. Ligament external and separated from the cartilage pit by a shelly plate. Schizothaerus nuttalli nuttalli Conrad Pacific Gaper Plate 31Z Washington to Lower California. Up to 8 inches in length. An oblongish to oval, strong, smoothish shell with a prominent gape at the posterior end. The neat, well-formed beaks are located M to % from the anterior end. The pallial sinus is very large and deep. Periostracum grayish. Common. Compare with the northern sub- species capax Conrad. Schizothaerus nuttalli capax Gould Alaskan Gaper Kodiak Island, Alaska, to Monterey, California. Up to 10 inches in length, differing from the typical nuttalli in being much more oval, more obese, and dipping downward into a well-rounded, ventral margin. This species is very common on most sandy and mud beaches in Puget Sound. Genus Rangia Desmoulins 1832 Rangia cuneata Gray Common Rangia Figure 91a, b Northwest Florida to Texas. I to 2% inches in length, obliquely ovate, very thick and heavy. The beaks which are near the oval, anterior end are high, inrolled and pointing downward and anteriorly. Exterior whitish, but covered with a strong, smoothish, gray-brown periostracum. Interior glossy, white and with a blue- gray tinge. Pallial sinus small, but moderately deep and distinct. A common fresh-water to brackish-water species found in coastal areas. R. iiasuta Dall is probably only a rostrate form of this species. Compare with R. flexuosa. Subgenus Rangianella Conrad 1867 Rangia flexuosa Conrad Brown Rangia Figure 91c, d Louisiana to Texas and Vera Cruz, Mexico. I to 1% inches in length, rescmbUng an elongate cuneata, but with no