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About H to % inch in length, shiny green-brown, with prominent con- centric sculpture and characterized by the nearly central umbones. Rostrum bluntly pointed, slightly upturned at the end. Concentric ribs disappear just anterior to the carinate border of the dorsal area which is strongly wrinkled. Adults over K' inch become quite fat. Commonly dredged off southern Cali- fornia in shallow water. Sorensen reports that this species is found com- monly in fish stomachs off Monterey. Nuculana penderi Dall and Bartsch Pender's Nut Clam Forrester Island, Alaska, to Santa Barbara, California. /4 to % inch in length, moderately elongate, very fat; rostrum short and pointed; concentric ribs prominent and evenly developed. Dorsal area of rostrum oval, finely ribbed and bounded by a sharp, smooth, large rib. Periostracum light-brown. Moderately common offshore. Nuculana hindsi Hanley Hinds' Nut Clam Nazan Bay, Alaska, to Costa Rica. % inch in length, moderately elongate (example: 7.8 mm. long; 4.4 mm. high; both valves 3.0 mm. wide); posterior end rostrate, slightly turned up at the end. Dorsal area of rostrum smoothish except for faint axial threads bounded by smooth carinate rib. Sculpture of evenly sized, closely spaced, distinct, concentric ribs which become obsolete just before the rostral rib. Exterior light yellowish brown. Interior white with faint pearly sheen. N. acuta Conrad, a name often given to this Pacific Coast species, has its rostral rib crossed by concentric ribs. N. penderi Dall and Bartsch is twice as fat, with a very ovate lunule and is more rounded at the ventral margin. Hanley in i860 first reported this species from "Gulf of Nicoya, Costa Rica." This is probably "N. re don do en sis" "Burch" 'oodring 1951. It is dredged com- monly off the West Coast from 1 5 to 600 fathoms. Subgenus Thestyleda Iredale 1929 Nuculana hamata Carpenter Hamate Nut Clam Figure z6A Puget Sound to Panama City, California. Under % inch in length, moderately compressed, exterior with strong concentric ribs; characterized by the squarely truncated posterior end of the long rostrum. Fairly commonly dredged off Calif ornian shores from 20 to 200 fathoms.