﻿PROSOBRANCHIATA. 209 



and front part of the whorl, but become obsolete over the middle and upper parts, 

 so as not to detract from the otherwise smooth and shining surface. The aperture is 

 of a narrowish, oval form ; the outer lip arched, projecting slightly towards the front, 

 thin, sharp-edged, and smooth within ; and the sinus wide, nearly semicircular, and 

 extending across the whole width of the margin 



The characters of this Pleurotorna are sufficiently well marked to merit distinction. 

 Although presenting a close resemblance to Pleurotorna tereticosta in the general 

 appearance, yet the smooth and shining surface of the shell, the more obtuse spire, the 

 greater width of the whorls, the thicker and more distant ribs, the more conical 

 form of the body-whorl, and the different condition of the sinus, separate the two 

 species. 



Size. — Axis, 5-1 2ths of an inch; diameter, 2-12ths of an inch. 

 Locality. — Potter's Bar. 



No. 192. Pleurotoma Fisheri. F. E. Edwards. Tab. XXXI, fig. 14, a, b. 



P. testa elongaid, turriculatd, longitudinaliter costatd, concentrice lineatd: spird 

 productd, acuminata: anfractibus brevibus, convexis, ad humeros angulatis ; marginibus 

 posticis latis, depressis, paululo cavatis, ad suturam tuberculatis ; cceterum lavibus ; idtimo 

 anfractu sub-conico ; costellis latiusculis, rotundatis ; lineis concentricis antice distantibus ; 

 supra partes medianas anfractuum numerosioribus, irregularibus ; supra margines posticas 

 obsoletis : aperturd ovali, in canali brevi, lato exeunti ; sinu lato, sub-trigono, anticd in 

 vtargine collocato. 



Shell long, narrow, turreted, longitudinally ribbed, and spirally lined ; the spire 

 pointed and much produced, forming nearly two thirds of the whole length of the 

 shell. The whorls, seven or eight without the pullus, are short, angular at the 

 shoulders, and nearly conical in front ; the posterior margins wide, depressed, a little 

 concave, and smooth, except on the sutural edge, where they present a single row 

 of rather large and distant rhomboidal knobs, divided by a transverse furrow across 

 the middle. The longitudinal ribs are short, broad, nearly vertical, rounded on 

 the upper surface, and separated by concave spaces as wide as the ribs, which, 

 in the last whorl, become reduced to oblong tubercles. The transverse lines are 

 sharp and elevated, distant, and separated by smooth, flat spaces over the front of the 

 whorls, but they become more numerous and irregular as they ascend the whorl from 

 the middle towards the shoulder, and are altogether lost on the posterior margins. 

 The mouth is of an oval form, and terminates in front in a wide and short, but 

 distinct canal; the outer lip is thin, sharp-edged, and slightly arched, and the sinus, 

 which is placed in front of the margin, is wide and somewhat triangular in shape. 



This Pleurotoma approaches most nearly to P. gomphoidea, but the more turreted 



