﻿PROSOBRANCHIATA. 



247 



the spire. The aperture is of an oblong-ovate form, and terminates anteriorly in 

 a short, but distinct and moderately wide, canal ; the outer lip is very slightly arched, 

 nearly straight, sharp-edged, and presents within, near the posterior extremity, 

 and immediately under the shoulder, a single large, tooth-shaped callosity ; the inner 

 lip is very narrow, barely extending to the front of the columella ; the sinus is nearly 

 triangular in form, deep and wide, extending across the whole of the posterior 

 margin. 



Size. — Axis, 3 - 4-12ths of an inch; diameter, r75-12ths of an inch. 

 Localities. — Highcliff, where it is not uncommon ; Havers tock Hill. 



No. 168. Pleurotoma gomphoidea. F.B.Edwards. Tab. XXVIII, fig. 13, a—f. 



P. testa angustd, elongatd, sub-turritd, longitudinaliter costatd, concentrice lineatd -. 

 spird acuminata, elevatd : anfraclibus depresso-convexis, ad humeros sub-angulalis ; 

 marginibus posticis latiusculis, concavis, ad suturam distanter granulatis ; ultimo anfractu 

 brevi, antice coarctato ; costellis curvis, brevibus, plus minusve numerosis ; lineis con- 

 centricis, supra margines fere obsoletis, cceterum elevatis, acutis, sa>pe denticulatis : 

 aperturd oblongo-ovali, in canali brevi, sub-recto exeunti ; labro sub-aliformi, acuto, sinu 

 lato, minime prof undo, in margine collocato. 



Var. avita, testa anfraclibus unicd serie tuberculorum coronatis. 



A long, narrow, turriculate shell, ribbed, and concentrically lined : the spire, 

 which forms two thirds of the whole shell, consists of seven or eight volutions : 

 the whorls are flatly convex on the sides, angulated at the shoulders, contracting 

 rather suddenly in front, and having the posterior margins widely channelled and 

 bordered on the sutural edge by a single row of round, rather distant granules, 

 corresponding with the ribs, and variable in size ; the angulated shoulders and 

 channelled margins give a turriculate character to the spire. The longitudinal ribs are 

 more or less numerous in different specimens ; they are curved, sharp, and terminate 

 abruptly where the whorl contracts ; the concentric lines over the posterior margins 

 are close-set, and so fine as to be barely visible to the naked eye ; over the middle 

 and front parts of the whorl they are moderately distant, elevated, sharp, and generally 

 denticulated where they cross the ribs. The aperture is of an oblong-oval shape, and 

 terminates in a wide, short, but distinct and nearly straight canal ; the outer lip is 

 expanded anteriorly, sharp-edged, and smooth within ; and the sinus, which is wide, 

 rather shallow, and rounded, is placed in the margin. 



I possess specimens both from Clarendon and Southampton, in which the ribs are 

 wanting, and the whorls are girt round the shoulders with a single row of knob-like 

 tubercles ; in all other respects these shells agree with the typical P. gomphoidea, 

 of which, therefore, I consider them to be a variety. 



