PROSOBRANCHIATA. 237 



ultimo anfraciu antice repentissime coarctato, in canali angusto, longiusculo, terminanti ; 

 lineis spiralibus confcrtis, inaqualibus, nonnullis eminentioribus, denliculatis : aperturd 

 oblongo-ovali ; labro valde arcuato, intus plicato ; sinu lato, sub-trigono, in margine collocato. 



Shell elongated, fusiform, tuberculated, and ornamented with very fine, concentric, 

 raised lines ; spire nearly conical and much produced, exceeding one half of the whole 

 shell in length ; whorls convex, sharply angulated at the shoulders, where they pre- 

 sent a single row of small, rather close-set, tooth-shaped tubercles ; the posterior 

 margins wide, frequently extending almost to the angle of the preceding whorl, slightly 

 channeled, and bordered round the suture by three sharp, elevated lines, crossed by 

 distant, oblique plications, corresponding with the tubercles on the shoulders of the 

 whorls ; the space between the suture and the shoulder is covered with very fine and 

 nearly equal concentric lines. The spiral lines over the middle and front parts of the 

 lines are numerous, very slender, but unequal ; every fourth or fifth line being rather 

 thicker and more prominent than the rest, and denticulated ; the intermediate lines 

 are simple, nearly equal, and so fine as to be barely perceptible by the naked eye. 

 The body- whorl is suddenly much contracted in front, and terminates in a narrow, but 

 not very long canal : the aperture is of an oblong oval form ; the outer lip much 

 arched and plicated within, and the sinus, which is wide and sub-trigonal in shape, 

 is placed a little in front of the middle part of the margin. 



The present species presents some resemblance to P. cymcea, but is easily distin- 

 guishable by the more elevated spire, the more numerous and smaller tubercles, the 

 character of the transverse ornamentation, and the shorter canal. 



Size. — Axis, 1 inch and 2-12ths; diameter, 5-12ths of an inch, nearly. 



Localities. — Highcliff, where it is very abundant, and Bracklesham Bay. 



Section I — Shells fusiform. ] 



A. Sinus in the posterior margin of the whorl. J 

 b. Canal short or indistinct* 



No. 159. Pleurotoma attenuata, Sowerby. Plate XXVII, fig. 6 a — c. 



Pleurotoma attenuata, Sow. 1816. Min. Con., vol. ii, p. 103, t. 146, fig. 1. 



— — lb. 1850. Dixon's Geol., &c, of Sussex, p. 102, t. 6, figs. 11,14. 



— — Morris. 1854. Cat. Brit. Foss., 2d edit., p. 269. 



* The sub-divisions dependent on the length of the canal are, it is unnecessary to say, merely artificial, 

 and towards the extremes of the two, species occur which may be referred, apparently with equal propriety 

 to either sub-division : in shells with a short canal, however, the anterior notch is generally wider and 

 deeper, and consequently the crest on the columella will be more prominent. 



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