450 American Seashells 



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 



