162 ARCADiE. 



Shell ovatc-lanceolato, thin, the posterior part double the length 

 of the anterior, narrowed to a point, the tij) being a little upturned, 

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

 terior side ovally rounded ; surface wrought into 

 numerous and crowded concentric folds, the in- 

 terspaces rather broadest, excepting a com- 

 pressed, lanceolate area l)ehind the beaks reach- 

 ing nearly to the tips, which is smooth and 

 shining ; a delicate, sub-marginal angle runs 

 from the Ijeaks to the lower angle of the trun- 

 cated tip, 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 pearly 

 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 ; Ijreadth, three tenths of an inch. 



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

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

 land^ ; Casco Bay (Mighels') ; Eastport and Grand Manan {Sthnp- 

 son) ; Plalifax (Willis). 



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 N. minuta, 

 from the coast of Norway, sent me l)y Dr. Loven, and can find no 

 difference in the numlier of teeth, or in any other respect. [This 

 comparison refers to the elongated and compressed form wdiicli is 

 still considered the typical form of iV. miuiita 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. pernula, but the striation is much 

 coarser, and there is lacking the lustre and radiating corrugations 

 of the epidermis found on that shell. 



