20 RECENT BIVALVE MOLLUSKS 



Crenella columbiana Dall. 1897. 



Aleutian Islands to San Dieg'o, Cal. 

 Crenella divaricata Orbigny, 1847. 



Santa Barbara Islands to Panama Bay. Also West Indies. 

 Crenella grisea Dall, 1897. 



Bering Sea to Sitka, Alaska. 

 Crenella rotundata Dall, 1916. 



Santa Cruz Island, Cal., in 155 fathoms. 



ORDER ANOMALODESMACEA. 

 A. ENSIPHONIA 



Family Periplomatidse 

 Genus Periploma Schumacher, 1817. 



Periploma planiuscula Sowerby, 1834. 



San Pedro, Cal., to Guayaquil. 

 Periploma discus Stearns, 1890. 



San Pedro Bay. Cal., to San Diego. 



Section Halistrepta Dall, 1904. 



Periploma sulcata Dall, 1904. 



San Pedro Bay, Terminal Island, Cal. 



Family Thraciidae 

 Genus Thracxa (Leach) Blainville, 1824. 



Thracia curta Conrad, 1837. 



Arctic Ocean, Bering- Sea, and south to San Diego, Cal. 

 Thracia beringi Dall, 1915. 



Bering- Sea, Aleutian Islands and southward to Sitka, 



Alaska. 

 Thracia challisiana Dall, 1915. 



Forrester Island, Alaska, to Gulf of Georgia. 

 Thracia diegensis Dall, 1915. 



San Diego Bay, Cal. 



Genus Cyathodonta Conrad, 1849. 



Cyathodonta dubiosa Dall, 1915. 



San Pedro to San Diego and the Gulf of California. 

 Cyathodonta pedroana Dall, 1915. 



San Pedro Harbor and Catalina Island, Cal. 



Genus Asthenoth?erus Carpenter, 1864. 



Asthenothaerus villosior Carpenter, 1864. 

 San Pedro, Cal., to Cape St. Lucas. 



