﻿PROSOBRANCHIATA. 



279 



Shell fusiform, elongated, turreted, concentrically lined: the spire pointed, elevated; 

 whorls, seven or eight, without thepullus, slightly convex ; the posterior margins con- 

 cave and plicated along the sutural edge, where they present two or three very fine, sharp, 

 elevated lines ; the shoulders obscurely angulated, and ornamented with a series of 

 rather distant tubercles, which on the early whorls are elongated, straight, and vertical, 

 but on the last whorl become pliciform and curved ; the last whorl is much contracted 

 in front and produced into a rather long and widish canal. The concentric lines over 

 the posterior margins and shoulders are close-set, regular, slender, and not very 

 prominent ; over the middle and front parts of the whorls they become more elevated, 

 thicker, and more distant, with very fine, thread-like lines occasionally intervening. 

 The aperture is of a narrow, elongated, oval form ; the outer lip slightly arched, 

 simple and smooth within ; and the sinus, placed on the shoulder, is very wide, 

 moderately deep, and triangular. 



A close comparison of the English shells with Belgian specimens has confirmed me 

 in the conclusion at which Mr. Morris and myself had arrived when a series of the 

 latter was first submitted to us by Sir Charles Lyell ; the shells from the two localities 

 agree so closely that I do not feel any doubt of their specific identity. 



It is a rare shell in England, although apparently abundant in Belgium, and in case 

 the position of the Limburg beds has been rightly determined, the occurrence of this 

 species in England is attended with additional interest from its being another 

 instance of the reappearance of shells of the London Clay period in the fauna of the 

 Upper Eocene epoch under nearly analogous mineral conditions. 



Size. — Axis, 1 inch and 7-12ths (40 millim.); diameter, 6-12ths of an inch (13 

 millim. nearly). 



Localities. — Highgate ; Hampstead Railway Tunnel ; Finchley ; Muswell Hill. 

 Belgian: Basele, Boom, Anvers (fide Be Kon.), Rupelmonde, Gremittingen (fide Nyst.) 



No. 204. Plburotoma Koninckii. Nyst Tab. XXIX, fig. 15, a, b. 



Pleurotoma l.-evigata. Be Kon. (non Sow.) 1837. Coq.. foss. de Basele, &c, p. 27, t. I, 



fig. 5. 



— Koninckii. Nyst. 1843. Bull. Soc. Geol. de Fr., vol. xiv, p. 454. 



— — Nyst. 1843. Coq. foss., &c., de Belg., p. 517, t. 41, fig. 3. 



B. testa elonyato-f usif ormi, concentrice linedta : spird elatd, acuminata : anfrdctibus 

 convexis, ad humcros in juventd arcuato-plicatis, deinde inermibus ; ad suturam, lineato- 

 maryinatis ; ultimo anfractu antice yradatim attenuato ; lineis concentricis confertis, sub- 

 reyularibus : aperturd oblonyo-ovali ; canali antico, lonyiusculo, anyusto ; labro lev iter 

 arcualo, ad humerum sinuato ; sinu Into, mcdiocriter prof undo, sub-triyono. 



A long, fusiform shell, ornamented throughout with concentric, raised lines; the 

 spire, formed of six or seven volutions without the pullus, is pointed and much 



