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EOCENE MOLLUSCA. 



callus, with the curved extremity of which it forms a wide, transverse groove, running 

 into the sinus ; the sinus is placed on the shoulder, and is wide, very deep, and 

 triangular in form. 



Specimens occur rather plentifully at Highcliff, constituting the variety raphium, 

 in which the shell is smaller and narrower, the spire more slender and pointed, 

 the margins of the whorls not so concave, and the concentric lines are moderately 

 distant, even, regular, and smooth. Another variety, moniligera, is also found, but 

 more rarely, in which the spire is longer, the elevated line bordering the posterior 

 margins of the whorls is coarsely granulated, and the median transverse lines are 

 more distant and more prominently denticulated. 



In the general aspect of the shell and the character of the ornamentation, this 

 Pleurotoma closely resembles the middle Eocene forms of P. denticula ; but the 

 callosities which present themselves on the inner surface of the outer lip indicate a 

 peculiar modification of the excretory tube protruded through the sinus, which 

 apparently entitles the present Pleurotoma to specific distinction. 



Size. — Axis, 8-12ths of an inch; diameter, 3-12ths of an inch. 



Localities. — Barton, Alum Bay (Stratum No. 29, Prestw.), Highcliff, where it is 

 abundant, and Brook. 



Section II. Shells fusiform. 



B. Sinus on the shoulder, 

 b. Canal short or indistinct. 



No. 216. Pleurotoma monerma. F. E. Edwards. Tab. XXXII, fig. 1, a — c. 



P. testa angustd, elongatd, turritd, undique concen trice lineatd: spird elevatd, in 

 longitudine bitrientes totius testa fere equanti, acuminata : anfractibus convexiusculis, 

 postice concavis, ad suturam bi-lineatis, ad Immeros sub-angulatis, noduloso-plicatis ; ultimo 

 anfractu per-brevi, in canalilato, indistincto exeunti ; plicis numerosis, verticalibus, arcuatis, 

 utrdque extremitate sub-nodulosis ; lineis concentricis supra margines posticas et humeros 

 anfractuum exilibus, confertis, equalibus, cceterum prominentibus, distantibus, irregularibus : 

 aperturd oblongo-ovali ; labro arcuato, simplici ; sinu lato, prof undo, sub-trigono, ad 

 humerum collocato. 



Shell narrow, elongated, turreted, and ornamented with concentric, raised lines, 

 which cover the whole surface ; the spire, formed of seven or eight whorls, exclusive of a 

 smooth, conical pullus of three volutions, is pointed and much produced, being nearly 

 twice the length of the aperture. The whorls are slightly convex and obscurely angu- 

 lated at the shoulders, where they present a series of regular, rather closely set, vertical 

 plications, transversely furrowed along the middle, and swelled into small tubercles at 



