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EOCENE MOLLUSCA. 



the sinus also is placed on the shoulder. The variety (fig. 3, a) somewhat resembles 

 the P. denticula of Basterot, and the other shell (fig. 3, b) more nearly approaches the 

 typical form of P. plebeia. Mr. Wood speaks of P. semicolon (Sow.) as being a 

 common and well-known Barton ^hell ; but I have never seen a specimen from that 

 locality. The species appears to be limited to the Bracklesham Bay sands and the 

 synchronous beds ; it is rare. 



Size. — Axis, 7-12ths of an inch (15 millim.); diameter, 2*3-1 2ths of an inch 

 (5 millim.). 



Localities. — Bracklesham Bay, Stubbington, Bramshaw, Brook. French: Grignon, 

 Mouchy (fide Desh.), Les Groux, Hermes, Cuisse-Lamotte, Ver, Acy-en-Mulcien 

 (fide Graves). 



No. 164. Pleuuotoma lepta. F. E. Edwards. Tab. XXVIII, fig. 10, a — c. 



P. testa parvd, fusiformi, gracili, spiraliter lineutd, semi-costellatd ; spird elevatd ; 

 anfractibus depresso-convexis, ad humeros angulatis ; postice unico sulco profunde exaratis, 

 ad suturam granulato-marginatis ; lineis spiralibus elevatis, acutis, haud distantibus ; 

 costellis crebris, per-brevibus : aperturd angusto-ovali, antice in canali brevi, indistincto, 

 terminanti ; sinu lato, semicirculari, in margine collocato. 



A small, slender, fusiform shell, spirally lined, and ribbed : the spire narrow, 

 pointed, elevated, forming nearly two thirds of the whole length of the shell : the 

 whorls flatly convex, angulated at the shoulders ; the posterior margins furrowed by 

 a deep sulcus, and somewhat thickened and granulated round the suture ; the 

 concentric lines elevated, sharp, and moderately close ; the longitudinal ribs rather 

 numerous, very short, not extending beyond the middle of the whorls, narrow, 

 and slightly oblique. The aperture is narrow, oval, terminating anteriorly in a wide, 

 short, indistinct canal ; and the sinus, which is wide and semicircular, is placed in the 

 margin. 



This species is closely allied to P. inflexa, but the shell is slenderer, with a more 

 broadly furrowed posterior margin ; the costellse also are shorter, the transverse 

 lineation more prominent, and the sinus wider and more rounded. 



Size. — Axis, rather more than 3-12ths of an inch; diameter, rather more than 

 1-1 2th of an inch. 



Localities. — Stubbington and Bracklesham Bay, at both of which places it is rare. 



