﻿246 



EOCENE MOLLUSCA. 



pullus, are slightly convex and angulated at the shoulders ; the posterior margins rather 

 wide, deeply channelled, and bordered by a series of closely-set, knob-like tubercles ; 

 the shoulders present a single row of oblong tubercles, divided by a concentric sulcus, 

 and from these tubercles arise narrow, curved costellae, which extend almost to 

 the very front of the whorl, and are decussated by sharp, concentric, raised lines, 

 not quite so prominent as the costellae, forming small tubercles at the points of 

 decussation ; the costellae and concentric lines, in the earlier whorls, are nearly 

 concealed by the succeeding whorl, and are only perfectly seen on the body-whorl. 

 The aperture is of an oblong-oval form, terminating in a wide, short canal ; the outer 

 lip is but slightly arched, sharp on the edge, and thickened and strongly plicated 

 within ; the sinus, which is placed in front of the margin, is wide, rather deep, and 

 sub-trigonal in shape. A variety occurs in which the shell is narrower, the spire 

 relatively longer, and the concentric lines more prominent. 



This seems to be a well-marked species, of which I have not been able to find a 

 foreign representative. 



Size.— Axis, 4-12ths of an inch ; diameter, 2-12ths of an inch. 



Localities. — Highcliff, where it is found rather abundantly, Alum Bay (No. 29, 

 Prestwich), Barton. 



No. 167. Pleurotoma dissimilis. F. E. Edwards. Tab. XXVIII, fig. 7, a — c. 



P. testa parvd, crassd, rugose costatd, omnino concentrice lineatd: spird brevi, obaisd, 

 nodulosd : anfractibus convexiuscidis, ad humeros sub-carinatis, postice sulco prof undo 

 spiraliier exaratis, marginatis ; costis brevibus, latis, rotundatis ; lineis concentricis plus 

 minusve numerosis, per-elevatis, denticulatis : aperturd oblong o-ovali, in canali brevi, 

 latiusculo exeunti ; labro sub-recto, acuto, intus unicam plicam dentiformem gerenti ; labio 

 angustissimo ; sinu lato, pro/undo, trigono, in margine collocato. 



Shell small, thick, coarsely ribbed, concentrically lined : the spire wide and 

 rather short, being less than two fifths of the whole length of the shell : the whorls 

 rather convex, slightly carinated at the shoulders, and bordered round the sutural 

 margin by a sharp, elevated, ridge-like line, the space between which and the 

 shoulder is traversed by a deep, round furrow, in which two or three feeble concentric 

 lines are seen. The ribs are few in number, very short, broad, rounded, and separated 

 by narrow furrows ; they become nearly obsolete, and frequently altogether lost on 

 the last whorl ; the concentric lines are sharp, much elevated, more or less numerous 

 in different specimens, and generally denticulated by the lines of growth. The 

 broad, short, posterior terminations of the ribs, left exposed by the overlapping of the 

 succeeding whorls, resemble tubercles, and give a coarsely nodulous character to 



