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EOCENE MOLLUSCA. 



denticulatd, cinclis, caterum lavibus ; ultimo anfractu conico, antice in canali palulo 

 indistincto, terminato, ad basin emarginato : aperturd anc/ustd, mb-quadratd ; labro arcuato, 

 acuta, intus plicato ; sinu latiusculo, sub-semicirculari, in margine cotlocato. 



Shell fusiform, somewhat turreted, longitudinally plicated, and transversely lined ; 

 the spire conical, pointed, elevated, forming rather more than half of the shell. The 

 whorls are sharply angulated at the shoulders ; the posterior margins slope gently back- 

 wards ; they are deeply channelled, and are bordered round the suture by an elevated 

 line, which, in some specimens, is sharp and ridge-like, in others denticulated ; the 

 hollow space between this line and the shoulders is smooth ; the last whorl is nearly 

 conical, and terminates in front in a wide, indistinct canal, slightly emarginate at 

 the extremity ; this form of the body whorl, with the conical spire, imparts to the 

 shell the appearance of two cones placed base to base. The longitudinal plications, 

 which extend to the very base of the shell, are numerous, narrow, oblique, curved, 

 and thickened at the points, where they are crossed by the transverse lines, into 

 small, tooth-like tubercles ; the transverse lines are moderately distant and sharp. 

 The aperture is very narrow and subquadrate, resembling that of the cones ; the 

 outer lip is moderately arched, sharp-edged, and strongly plicated within ; the 

 sinus, which is placed in the margin, is rather wide and nearly semicircular. 



Some shells from Lethen and Vliermael have been referred by Nyst to this species, 

 although with doubt ; judging from the figure given by that author, the margins of the 

 whorls in those shells appear to be narrower, and the longitudinal plications thicker and 

 less numerous, than in this species, and the body whorl is convex, contracted in front, 

 and terminates in a perspicuous canal ; the shells in question are, in fact, quite distinct 

 from the " testa ecaudata, utrinque sub-coniea," described by Solander, and D'Orbigny 

 has distinguished them as P. sub-conoides. 



Size. — Axis, 9-12ths of an inch; diameter, nearly 4-12ths of an inch. 



Localities. — Barton, Highcliff, Alum Bay (No. 29, Prestwich). 



No. 243. Pleurotoma biconus. F. E. Edwards. Tab. XXXIII, fig. 7, «, b. 



P. testa biconicd, concentrice lineatd : spird sub-turritd, acuminata: anfractibus ad 

 humeros angulatis, granoso-tuberculatis ; postice cavatis, ad suturam lined fastigiiformi 

 cinctis, caterum lavibus ; antice sub-rectis : lineis concenlricis elevatis, acutis, sub-dis- 

 tantibus, interstitiis concavis : aperturd angusto-ovali, in canali patulo indistincto exeunte ; 

 labro leviter arcuato, acuto, intus plicato ; sinu lato, breviusculo, sub-trigono, in margine 

 cotlocato. 



Shell doubly cone-shaped and concentrically lined ; the spire, w T hich is a little 

 shorter than the aperture, is somewhat turreted and pointed. The whorls, five or six 

 without the pullus, are rather sharply angulated at the shoulders, which present 



