﻿PROSOBRANCHIATA. 



309 



deep, and triangular, is placed on the shoulder, and the columella is twisted, and bears 

 a single, oblique, and obscure, fold-like callus near the middle.* 



This, as well as the preceding, species presents a close analogy with a Pleurotoma 

 from the lower Eocene deposits of Germany, figured, but not as yet described, by 

 Beyrich (' Norddeuts. Tertidrgeb.' tab. xxix, fig. 3) ; and for the reasons before stated, 

 the identity cannot be satisfactorily ascertained. 



Size. — Axis, 7-1 2ths to 9-12ths of an inch, nearly; diameter, rather more than 

 3-12ths of an inch, nearly 4-12ths. 



Localities — Highgate, Potter's Bar. 



No. 235. Pleurotoma parilis. F. E. Edwards. Tab. XXXI, fig. 10, a — c. 



P. testa oblongo-fusiformi, undigue concentrice lineatd : spird sub-conicd clevatd : an- 

 fractibus convexiusculis, ad humeros obtuse angulatis, inermibus ; marginibus posticis latis, 

 concavis, ad suturam exilissime crcnidatis ; ultimo anfractu sub-conico, in canalcm brevem, 

 latiusculum,prolongato ; lineis concentricis confertis, supra partes anticas mediasque anfrac- 

 tuum inaqualibus, lineis incrementi asperatis ; supra margines regularibus, granulatis : 

 aperturd oblongo-ovali ; labro tenui, sub-semicirculari ; sinu prof undo, marginibus sub-paral- 

 lelis, ad humerum collocato ; columella contortd, callosd. 



Shell elongated, fusiform, and covered with numerous, fine, concentric, raised 

 lines ; the spire, formed of seven or eight volutions exclusive of the pullus, is pointed, 

 nearly conical, and moderately elevated, equalling the aperture in length. The whorls 

 are slightly convex, with broad, concave margins, and are separated by a deep, well- 

 defined suture, along the edge of which they present a series of fine crenulations, which 

 give a wrinkled appearance to the margin ; in the early whorls the margins overlap 

 the preceding whorls up to the shoulders, but in the later whorls the shoulders are 

 more exposed. The last whorl is nearly conical, and terminates in front in a mode- 

 rately wide and short, but distinct, canal. The concentric lines are closely set ; over 

 the front and middle of the whorls they are irregular and unequal, very slender 

 lines alternating with thicker, thread-like lines, and they are roughened, almost 

 granulated, by the lines of growth ; over the margins and shoulders, the concentric 

 lines are even, regular, and finely granulated. The aperture is of an oblong-oval 

 form ; the outer lip is much arched, almost semicircular, thin, sharp on the edge, and 

 smooth within, and it presents at the shoulder a wide and very deep sinus, with 

 nearly parallel margins and a rather widely rounded extremity ; the columnella is 

 slightly twisted, and bears about the middle an obscure, oblique, fold-like callus. 



* The callus on the columella of P. granata,P. parilis, and of some other shells referred to Pleurotoma, 

 suggests the propriety of placing those species among the Borsonice ; but this callus is not, in fact, a true 

 fold, but merely a thickening caused by the contortion of the columella; and, therefore, the species in 

 which it is found are carefully excluded by Bellardi from his genus. 



