NYMPIIACEA. MOLL use A. LUCINA. 71 



Shell white, thin, rounded, regularly convex, sub-equilateral ; 

 beaks elevated, inclined forwards, in front of which is a long and 

 narrow areola somewhat crested. Surface glossy ; stages of 

 growth strongly marked ; deeply sculptured with regularly dispos- 

 ed and nearly parallel lines, flexed at nearly right angles along the 

 anterior third, so as to pass obliquely downwards towards both 

 ends, and forming teeth around the entire margin, most prominent 

 behind. Hinge margin nearly straight. Teeth, one in the right 

 valve, very small, and two small, diverging ones in the left valve. 

 Lateral teeth wanting or rudimentary. Ligament almost entirely 

 concealed. Length 1 inch, breadth | inch, height y% inch. 



This shell, so remarkable for its universal dispersion, as well in a 

 fossil, as in a living state, is not unfrequently thrown upon our ocean 

 shores in such a state as to indicate a neighbouring residence. At 

 Nantucket, it is far from rare. It is found on every Atlantic shore 

 even to the Southern Ocean, and also in all the tertiary formations of 

 Europe. 



It varies considerably in the developement of the lateral teeth, and 

 in the approximation of the strise. 



Luci'na flexuo'sa. 



Shell small, while, globose triangular; a deep fold along the 

 posterior margin renders the base sinuous ; hinge with only a single 

 rudimentary tooth in each valve. 



Figure 52. 



State Coll., No. 196. Soc. Cab., No. 2413. 



Tellina flexuosa, Montagu ; Test. Brit., 72. Pennant ; Brit. ZooL, iv. 183. 



Rackett; Lin. Trans., viii. 56. Wood; Gen. Conch., 188, t. 47, f. 7, 8. 



DiLLWYN ; Catal.,99. Turton ; Conch. Diet., 177. 

 Venus sinuosa, Donovan ; Brit. Shells, ii. pi. 42, f. 2. 

 Crj'ptodon flexuosa, Turton ; Brit. Biv., 121, pi. 7, f. 9, 10. 



Shell minute, white, ovate-globose, or somewhat triangular, 

 nearly equilateral ; beaks prominent, inclined forwards, and having 

 a rounded depression in front of them ; behind them, a remark- 

 able widened groove runs near the margin to the posterior base, 

 producing a deep indentation in the outline of the margin at that 

 part ; elsewhere regularly rounded ; surface smooth, dead white. 



