NUCULA. 153 



Shell trapcziform, inflated, beaks at anterior fourth, prominent, 

 rather obtuse, angle of dorsal margins at the beaks a right angle, 

 anterior slope nearly vertical, with a broad heart-shaped lunule de- 

 fined by a rather acute ridge, with the included edges of 

 the valves a little pouting, and marked l)y very faint di- 

 verging strife ; posterior dorsal margin for about half its 

 length nearly horizontal and then obli(iuely truncate, so as 

 to make the hinder end biangular, and so that the acutely N^^7!!fia- 

 rounded tip is near the ventral mai'gin ; the posterior dor- '"' 

 sal face is broad, lozenge shaped, defined by a pretty distinct umbo- 

 nal ridge, the valve edges compressed and the color paler ; epidermis 

 yellowish green, shining, rather coarsely striate concentrically. In- 

 terior silvery, margin simijle, hinge with about five teeth before and 

 ten behind the large oblique ligament cavity. Length, three tenths 

 of an inch ; height, five twentieths of an inch ; breadth, three 

 twentieths of an inch. 



Dredged by Dr. Packard at Henley Harbor, Labrador ; Greenland 

 (il/d//e/-) ; Arctic Seas (^Hancock}. 



Generally resembling iV. tenuis, but more inflated, and angular iu 

 all its outlines. 



Nucula delphinodonta. 



Shell minute, triangular, oblique, very broad, beaks nearly terminal, three an- 

 terior and seven posterior teeth. 



Nucula delphinodonta, Mighels, Best. Journ. Xat. Hist. iv. 40, 324, pi. 4, fig. 5 (1842). 



Stimpsox, Shells of New England, 9; Proc. Bost. Soc. iv. 13; Inv. Gr. Manan, 

 20. — MoRCii, Prod. Moll. Granl. 21. 



Nucula corticata, IIolboll and Moller, fide Morch. 



Shell quite small, obliquely triangular, very broad, and tumid, 

 beaks nearly at the posterior point ; posterior margm nearly vertical, 

 passing Ijy a rounded right angle into the slightly curved 

 ventral margin ; anterior dorsal margin descending at an ^'^' ^^^' 

 angle of 45° and terminating in an acutely rounded point ; 

 dorsal face broad, beaks elevated and tumid, with a deep n. mpm- 

 heart-shaped excavation under the beaks bordered by a "'"'°'''«- 

 delicate but acute ridge running to the basal angle ; a ^ 



smooth, flattened, lanceolate area in front of the beaks ; surface wdth 

 coarse unequal striae of growth ; epidermis olivaceous. Hinge with 

 three posterior and seven anterior sharp, elongated teeth. Length, 

 thirteen hundredths of an incli ; height, eleven hundredths of an 

 inch ; breadth, nine hundredths of an hich. 



