PROSOBRANCHIATA. 323 
of two unequal cones placed base to base, the smaller one of which is represented by 
the spire ; the whorls, seven or eight without the pullus, are straight on the sides and 
taper regularly towards the base; the posterior margins slope gently backwards, con- 
cealing the preceding whorl up to the angle of the shoulder, giving a straight-sided, 
conical shape to the spire, which forms about two fifths of the entire length of the 
shell. Two or three narrow, obscure furrows traverse the space between the suture 
and the shoulders ; and the front of the last whorl also presents numerous transverse, 
undulating furrows, the ridges between which are a little roughened by the lines of 
growth; the remaining surface of the whorls is smooth and shining. The aperture is 
long and narrow, with nearly parallel margins, resembling that of a Cone, and terminates 
in front in a wide, short, and indistinct canal, deeply notched at the anterior extremity. 
The outer lip is much arched, and presents on the shoulder a very wide, shallow sinus, 
with a broadly rounded apex ; the inner lip is elevated and bent outwards at the base, 
giving an umbilicated appearance to the front of the shell; and the columella is cylin- 
drical and strongly crested. 
The present species is distinguished by the inequality of the two cones of which it 
appears to be formed, and by that character and by the wide, shallow sinus it may 
be easily separated from P. prisca, which, in other respects, it resembles. It does 
uot appear to have an analogue among the French coniform Pleurotome. 
Stze.-—Axis, 24 inches ; diameter, | inch. 
Locality.—Bracklesham Bay, to which it appears to be peculiar. I have not met 
with it elsewhere, not even at Stubbington or Bramshaw. 
No. 247. Prevuroroma semisrriata. Deshayes, Tab. XXXIII, fig. 3 a, 5 0. 
PLEUROTOMA SEMISTRIATA. Desh. 1824-37. Desc. des Coq. foss., &e., vol. 11, p. 443, t. 69, 
figs. 5, 6. 
Non PLEUROTOMA SEMISTRIATA. Partsch. 1837. v. Hauer. Vorkomm. foss. Thierr. tert. Beck. v. 
Wien; Jahrb., p. 419, No. 107. 
P. testd biconicd, transversim obsolete lineatd ; spird elatd, acuminata ; anfractibus 
conveaiusculis, postice obsolete sulcatis; ultimo anfractu gradatim attenuato, conoidco, 
concentrice distanter et exilissime lineato, antice transversim sulcato, ad basin sub-profunde 
emarginato : apertura elongato-angustd ; labro acuto, aliforme, arcuato ; sinu lato, trian- 
gulari, in margine collocato. 
Shell elongated, fusiform, tapering gradually towards each extremity and presenting 
the appearance of two cones placed base to base ; the spire moderately elevated, nearly 
equalling the last whorl in length, and pointed. The whorls, seven without the pullus, are 
slightly convex, smooth and shining; the posterior margins, which slope gently back- 
wards, present two or three very shallow, nearly obsolete, concentric furrows ; the last 
