238 EOCENE MOLLUSCA. 



Nee Pleuromoma attenuata, Desk. 1824-37. Descr. des coq. foss., &c., vol. ii, p. 483, t. 68, 



figs. 6, 8. 

 nee Dujar. 1837. Mem. Soc. Geol. de France, vol. ii, p. 291, t. 20, 



fig. 22. 



P. testa elongato-fusiformi, turritd, costatd, undique spiraliter lineatd : spird elevatd, 

 acuminata ; anfractibus angulatis, unicd serie nodorum spiniformium, costas coronantium, 

 armatis ; marginibus posticis latis, declivis, concavis, ad suturam pauxillum incrassatis, 

 tenuiter crenulatis ; ultimo anfractu antice sensim attenuato, in canali longiusculo, lato, 

 terminanti ; costis brevibus, sub-distantlbus, rotundalis ; lineis spiralibus numerosis, in 

 marginibus tenuibus ; cetaris inaqualibus .• aperturd lanceolatd ; labro arcuato j sinu lato, 

 subtrigono, in margine collocato. 



Shell elongated, fusiform, turreted, longitudinally ribbed, and ornamented with con- 

 centric raised lines: the spire, formed of eleven or twelve volutions exclusive of the pullus, 

 is much elevated and pointed ; the whorls, angulated at the shoulders, are gradually 

 attenuated towards the base, assuming an almost conical form ; the body-whorl termi- 

 nates in a wide, moderately long canal, rather deeply notched at the anterior extremity ; 

 the posterior margins are wide, slightly bent towards the preceding whorls, channeled 

 along the middle, thickened at the sutural edge, and bordered by two thickish, promi- 

 nent, raised lines, granulated or feebly plicated by the lines of growth. The ribs are 

 rather distant, short, oblique, rounded, and terminate at the shoulder in large, trans- 

 versely compressed, spiniform tubercles, the bases of which are frequently prolonged 

 backwards half-way across the posterior margin. The whole surface of the whorls is 

 covered with close-set concentric raised lines, which are thread-like and nearly equal 

 on the margins, but irregular and unequal over the middle and front parts of the 

 whorls ; one or two more or less slender lines intervening between thicker and more 

 prominent lines : the whole surface is roughened by the lines of growth, which in the 

 Bracklesham Bay specimens are very prominent, and give a coarse, rugged character 

 to the shell. The aperture is of a long, narrow, lanceolate form ; the outer lip mode- 

 rately arched ; and the sinus, which is wide, not very deep, and sub-trigonal in shape, 

 is placed in the margin. The columella is nearly straight, and presents a large promi- 

 nent crest or comb at the anterior extremity. 



M. Deshayes (loc. cit.) has given the specific name attenuata to certain shells from 

 the older eocene beds of France, quite distinct from the present species, to which, in 

 point of priority, the name belongs ; and Dujardin has fallen into the same error with 

 regard to a Pleurotoma from Touraine. D'Orbigny, in his ' Prodrome/ has distin- 

 guished the French eocene shells by the name sub-attenuata, and the miocene shells by 

 that of pseudo-attenuata. 



Size. — Axis, 4 inches, nearly ; diameter, 1 inch and 2-12ths. 



Localities. — Although Mr. Sowerby (Dixon's ' Sussex/ p. 1 02) and Mr. Morris 



