CHAPTER XXV: THE NUT SHELLS 



Family NucuLiOi^ 



Shell bivalve, three-cornered or oval, small, pearly inside, 

 hinge formed of small, comb-like teeth, interrupted by a central 

 pit for the ligament. 



Genus NUCULA, Lam. 



Shell with beaks turned toward the short posterior side; 

 epidermis alive; hinge teeth sharp, comb-like; foot large, fissured, 

 expanding into a fringed disk at tip; gills small, plume-like. 

 About fifty species of small burrowing mollusks, chiefly in cold seas. 



The Thin Nut Shell (N. tenuis, Montagu) is about as big 

 as a grain of corn. Its smooth thin shells are protected by a 

 bright green epidermis. This plain little shell is found north- 

 ward from Maine and along all coasts of northern Europe. 



N. proxima, Say, is a trifle larger, with an olive skin protect- 

 ing the finely cancellated surface, and crinkled margins. This 

 is the common little nut shell of the Atlantic coast to North 

 Carolina. It occurs also in western Florida. 



A few other species are found on our colder coasts. 



The Camp Nut Shell (N. castrensis Hds.) is a triangular 

 brown shell, with sculptured markings, like an array of tents, on 

 the surfaces. Inside it is pearly. The valves are no larger than 

 half of a navy bean. 



Habitat. — Deep water, California to Alaska. 



Genus LEDA, Schum. 



Shell oblong, produced into an angle behind, usually rounded 

 in front; margins not scalloped; hinge teeth as in Nucula; ani- 

 mal has two unequal siphon tubes, partly joined; mantle margins 

 forming a third siphon in front; gills narrow, plume-like About 

 eighty species, widely distributed in cold seas. 



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