NUCULA. 153 



Shell trapeziform, inflated, lieaks at anterior fourth, prominent, 

 rather obtuse, anoio of dorsal margins at the Ijeaks 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 stria3 ; posterior dorsal margin for about half its 

 length nearly horizontal and then o])li(iuely truncate, so as 

 to make the hinder end biangular, and so that tlie acutely jv.^a- 

 rounded tip is near the ventral margin ; the posterior dor- 

 sal face is broad, lozenge shaped, defined by a pretty distinct uml)0- 

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

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

 terior silvery, margin simple, hinge with al)out five teeth Ijefore 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 l)y Dr. Packard at Henley Harbor, Labrador ; Greenland 

 {Mbllcr) ; Arctic Seas {Hancock). 



Generally resembling N. tenuis, but more inflated, and angular in 

 all its outlines. 



Nucula delphinodonta. 



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

 terior and seven posterior teeth. 



Nucula delphinodonta, MiGiiELS, Bost. Journ. Nat. Hist. iv. 40, 3-24, pi. 4, fig. .5 (1842).— 

 Stimpsox, Shells of New England, 9 ; Proc. Best. See. iv. 13 ; luv. Gr. Manan, 

 20. — Moiicii, Prod. Moll. Grrenl. 21. 



Nucida curtirata, Holboll and Moller, fide Morcii. 



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

 beaks nearly at the posterior j>oint ; i)Ostcrior marghi nearly vertical, 

 nassinu' by a rounded right anule into the sliglitly curved 

 ventral margm ; ant(n'iur dorsal margin descendmg at an 

 angle of 45° and terminating in an acutely rounded j)oint ; 

 dorsal face broad, l)eaks elevated and tumid, with a deep 

 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 with 

 coarse unequal striae of growth ; epidermis olivaceous. Hinge with 

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

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

 inch ; breadth, nine hundredths of an inch. 



