﻿290 



EOCENE MOLLUSCA. 



tubercles, as already observed, are due to the thickening of the extremity of the sinus, 

 for the more easy protrusion of the excurrent siphon, and they may be reasonably pre- 

 sumed to be liable to variation ; and, with regard to the plication of the outer lip, 

 I have adverted to the occurrence of specimens from Bramshaw, in which that cha- 

 racter is found. On these grounds I have considered that the shells described by 

 Sowerby as P. plebeia ought to be referred to Basterot's P. denticula, although the 

 figure given by Basterot is well calculated to lead to a different conclusion. 



Size. — Axis, rather more than 1 inch (26 millim.); diameter, not quite 4-12ths of 

 an inch (8 millim.) 



Localities. — London Clay: Highgate, Potter's Bar, Southampton, Clarendon, Alum 

 Bay (Stratum No. 4, Prestw.) Middle Eocene: Bracklesham Bay, Stubbington, 

 Brooke, Bramshaw, Highcliff, Barton, Alum Bay (Stratum No. 29, Prestw.), 

 Brockenhurst. Upper Eocene: Lyndhurst, Hordwell, Colwell Bay, Headon Hill, 

 St. Helen's. French: Environs of Bordeaux, Dax, Touraine. Ltalian : Tortona, 

 Environs of Turin. Belgian: The Bolderberg, near Hasselt. 



No. 214. Pleurotoma crebrilinea. F. E. Edwards. Tab. XXX, figs. 8, a — c. 



P. testa elongato-fusiformi, turritd, omnino transversim subtiliter lineatd: spird 

 obtusmsculd, elevatd: anfractibus depresso-convexis, ad humeros fasciold elcvatd ceu carina 

 cinctis, postice concavis, viarginatis ; ultimo anfractu brevi, cyathiformi, anlice valde 

 coarctato : aperturu ob-ovatd, in canali longiusculo exeunti ; labro leviter arcuato, ad 

 humerum sub-triangulariter sinuato. 



A long, fusiform, turreted shell, ornamented with numerous concentric, raised 

 lines ; the spire, formed of eight or nine volutions, is rather obtuse, and moderately 

 elevated, forming half the length of the entire shell. The whorls are very slightly 

 convex on the sides, deeply furrowed round the posterior margins, and angulated at 

 the shoulders, round which they are girt by an elevated, ribbon-like band, forming an 

 obtuse keel ; the last whorl is short and much contracted in front, which imparts to it 

 a cup-like form. The whole surface of the whorls is covered with numerous, very fine, 

 close-set, raised lines ; these lines, over the posterior margins of the keel, are equal 

 and regular, but over the middle and front parts of the whorls they become unequal, 

 other lines, slightly thicker and more prominent, occasionally intervening between the 

 slender lines. The aperture is nearly oval in form, and terminates in front in a mode- 

 rately long and nearly straight canal ; the outer lip is but slightly arched and smooth 

 within, and it presents at the shoulder a wide, three-cornered sinus. 



I feel much hesitation in separating this Pleurotoma from P. denticula, of which it 



