﻿248 



EOCENE MOLLUSCA. 



Size. — Axis, rather less than half an inch ; diameter, not quite 2-12ths of an inch. 

 Localities. — Barton, Highcliff, Alum Bay (No. 29, Prestwich). For the variety ; 

 Clarendon and Southampton. 



No, 169. Pleurotoma plicata. Lamk. Tab. XXVIII, fig. 11, a — c. 



Pllurotoma plicata. Lamk. 1804. Ann. du Mus., vol. iii, p. 169, No. 14. 







Lamk. 1822. Hist, natur., &c, vol. vii, p. 100, No. 19. 







Desk. 1824-37. Descr. des Coq. foss., &c, vol. ii, p. 487, t. 66, 







figs. 17—19. 



Nec — 





Bast. 1825. Mem. Geol. sur les Env. de Bord., p. 64, No. 6. 



nec — 





Des Moul. 1834. (Dufrem Terr, tert., &c, du Midi de la France.) 







Ann. des Mines, 3d series, vol. iii, p. 122. 



nec — 





Phil. 1836. Enum. Moll. Sicil., p. 198, No. 5. 



nec — 





Grat. 1847. Conckyl. foss., &c, du bass, de l'Adour (Atlas) ; 



Pleurot., t. 2, No. 20, fig. 36. 



P. testa crassd, elongato-fusiforwi, angustd, longitudinaliter costatd, omnino concentrice 

 lineatd : spird mediocriter elald, sub-acuminatd : anfractibus convexis, suturd perspicud 

 divisis ; costis rotundatis, obliquis, arcuatis, distantibus ; lineis concentricis JUift rmibus> 

 regularibus : aperturd angustd, ovali, in canali brevi exeunti ; labro acuto, intus int assato' 

 posfice,prope sinum,callum nodiformem gerente ; sinu lato, prof undo, sub-trigono, in :>iargine 

 collocato. 



Shell thick, elongated, fusiform, rather narrow, longitudinally ribbed, and having 

 the whole surface covered with concentric, raised lines ; the spire, which consists 

 of six or seven volutions, exclusive of the pullus, is moderately elevated, forming 

 nearly one half of the whole length of the shell ; the whorls convex, and separated by 

 a perspicuous suture. The longitudinal ribs are prominent, rounded, oblique, slightly 

 curved, distant, numbering only six or seven on each whorl, and becoming nearly 

 obsolete on the body-whorl ; the intermediate spaces are nearly flat, imparting 

 a polygonal aspect to the spire ; the concentric lines are rather numerous, elevated, 

 rounded, clearly defined, and regular, giving to the shell the appearance of being- 

 bound with thread ; the two or three lines over the shoulder are, in general, more 

 distant, and a very little more prominent, than the others. The aperture is of a 

 narrow, oval form, and terminates in a wide, short canal ; the outer lip is moderately 

 arched, sharp on the edge, much thickened within, where it presents a long, rather 

 broad, and elevated ridge, extending quite into the canal, and terminating behind, 

 immediately in front of the sinus, in a round, knob-like callus ; the sinus is broad, 

 deep, somewhat triangular in shape, and placed in the margin. 



The English shells present several points of disagreement with those from the 



