150 ARCADJ;. 



This shell is very similar to the following, and would not at once 

 be distinguished from it. The following are some of the essential 

 differences. The anterior margin, instead of running straight to the 

 anterior tip, runs aljout half the distance parallel with the 

 Fig. 45.. i3ase, then forms an angle, and, by a broadly rounded curve, 

 joins the curve of the base ; the tip is, therefore, not point- 

 ed as in N. proxima, and the angle of this end gives the 



N. tenuis. . . . 



shell a four-sided, instead of a triangular figure, the greatest 

 height being somewhat before the beaks ; beaks prominent, curved 

 backwards, and having a deep pit behind them, not found in the 

 other s])ecies ; posterior margin forming as much as a right angle 

 with the anterior ; while in N. proxima we have rather less than a 

 right angle. The surface is smooth, glossy, grass-green, without any 

 radiating lines. Interior a silvery- white, but not pearly like the 

 other. The teeth are very long and slender, scarcely if at all folded, 

 and only about eight before and four or five behind the beaks. The 

 interior margin is always simple, but never so in the smallest 

 specimens of JV. proxima. The shell is very thin, and its breadth 

 very small. Length, three tenths of an inch ; height, one quarter 

 of an inch ; breadth, three twentieths of an inch. 



Found in the stomachs of fishes, but much more sparingly than 

 the following. Casco Bay {Mig-hc/s) ; Eastport, rare in fifteen to 

 twenty fathoms {Cooper^; Halifax, Sambro Banks {Willis); St. 

 Anne, Capuchin, &c. {Bell) ; Northumberland Sound and Port 

 Refuge {Belcher) ; Labrador {Packard) ; Northern coasts of Eng- 

 land ; Drontheim to North Cape {McAndreic). 



This shell, as far as I can recollect, is the one in the collection of 

 the Academy of Natural Sciences at Philadelphia, marked " N. 

 lucida, Blanding." It corresponds precisely with a specimen of 

 Nucula tenuis sent me by Mr. Sowerby, and it is his opinion that 

 they arc identical. 



Nucula proxima. 



Fjg. 63. 



Shell oblique, ovate-triangular, anterior end perpendicular to the base ; crossed 

 by minute, concentric, and radiating lines; epidermis olivaceous; within pearly, 

 margin crenulated ; teeth, twelve before and eighteen behind the beaks. 



Area micleus, Lin. Syst. Nat. 114.3 (in part, prohahly). — Doxov. Br. 8h. ii. fi3 ; Chenu ed. 

 Nucula margaritacea. Lam., Brown, 111. Conch. G. Br. 85, pi. 33, fig. 12. 

 Nucula nucleus, Forbes and Hanl. Br. Moll. ii. 215, pi. 47, figs 7, 8. — Hanley, in 

 Thes. Conch, iii. 148, pi. 229, figs. 121, 122. — Loven, Ind. Moll. Scand. 34. 



