162 ARCADE. 



Shell ovate-lanceolate, tliin, the posterior part donhlc the length 

 of the anterior, narrowed to a point, the tip being a little upturned, 

 truncated and gaping, the upper margin straight and sharp ; an- 

 terior side ovally rounded ; surface wrought into 



Fiff. 4G8. 1,1 -, 



numerous and crowded concentric folds, the in- 

 terspaces rather broadest, excepting a com- 

 pressed, lanceolate area behiml the licaks reach- 

 ing nearly to the tips, which is smooth and 

 shining ; a delicate, sul)-marginal angle runs 

 from the beaks to the lower angle of the trun- 

 cated tij), at which the concentric folds or ril)S 

 are bent at nearly a right angle, so as to be parallel to the margin ; 

 epidermis light greenish-yellow, or sap-green color, within ])early 

 white ; an elevated ridge runs from within the cavity of the beaks 

 to the lower angle of the truncated tip, corresponding to the ex- 

 terior angle ; teeth twelve to fourteen before the beaks, and sixteen 

 to eighteen behind them. Length, one inch ; height, nine twen- 

 tieths of an inch ; breadth, three tenths of an inch. 



Found, not very rarely, in the stomachs of fishes taken off Na- 

 hant. Provincetown Harbor ( Tottcn) ; off Isle of Shoals ( Wheat- 

 land) ; Casco Bay {MigheJs~) ; Eastport and Grand Manaii {Siinip- 

 son^; Halifax (Wi/lis}. 



This shell is readily distinguished from our other species by the 

 folds and grooves of its surface. It is much more pointed than the 

 other species, and does not attain to a large size, the above dimen- 

 sions being those of a shell one third longer than the usual size. I 

 have carefully compared our shell with a specimen of iV. niimita, 

 from the coast of Norway, sent me by Dr. Loven, and can find no 

 difference in the number of teeth, or in any other resi)ect. [This 

 comparison refers to the elongated and compressed form which is 

 still considered the typical form of iV". mimda in the British Mol- 

 lusca, but which Mr. Hanley has since separated, rightly, as I think, 

 to represent the N. caudata of Donovan as a distinct species. Our 

 shell is somewhat more elongated and less recurved, and grows to a 

 much larger size ; still, the distinction is not positively marked. In 

 size and form it is more like L. permda, but the striation is much 

 coarser, and there is lacking the lustre and radiating corrugations 

 of the epidermis found on that shell. 



