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Rh Nucula atacellana Schenck Cancellate Nut Clam Figure yoe Massachusetts to Maryland. Vs inch in length and oval in outline; the cancellate sculpturing is due to the crossing of numerous radial and concentric threads. Interior scarcely pearly and with a thick, transparent glaze. Color yellowish brown to light- tan. Commonly dredged offshore down to 500 fathoms. Formerly known as N. reticulata Jeffreys and cancellata Jeffreys. Nucula crenulata A. Adams Atlantic Crenulate Nut Clam South Carolina to Key West, Florida. % inch in length, ovate, internal margin finely crenulate. With numer- ous concentric, fine ribs which have numerous microscopic crenulations be- tween them. Interior scarcely pearly; overlaid by a thick, transparent layer of shell matter, through which radial fractures or lines are discernible; color yellowish. Dredged in shallow water. Similar in outline to N. tenuis (see fig. 70c). Nucula exigua Sowerby Pacific Crenulate Nut Clam Southern California to Ecuador. %6 inch in length (5 mm.), shaped hke tenuis and the preceding species. Concentric rings strong with radial crenulations between. Strongly project- ing lunular area just under the beaks. Color yellowish. Dredged in shallow water. Very similar to N. crenulata from the Western Atlantic. Nucula delphinodonta Mighels Delphinula Nut Clam Figure jod Nova Scotia to Maryland. Vie inch (3 mm.) in length, ovate, fat and smooth except for coarse concentric growth lines. Anterior end slightly pushed in under beaks and bordered by slight carination. Ventral edge smooth. Color olive-brown. 9 teeth posterior to and 4 teeth anterior to chondrophore. Nucula tenuis Montagu Smooth Nut Clam Figure 70c Labrador to Maryland. Alaska to Lower California. Usually %6 inch in length (up to % inch in Alaska), ovate, smooth except for irregular growth lines. Color a shiny olive-green, sometimes with darker lines of growth. No radial lines. Ventral edge smooth.