228 EOCENE MOLLUSCA. 
arched, and the sinus, which is wide and almost semicircular in shape, occupies the 
whole width of the margin. 
Specimens occasionally occur in which the transverse lineation is nearly obliterated, 
and the whorls present a smooth, almost a polished, surface. The individuals figured 
by Mr. Sowerby were apparently in this condition ; this smoothness, from which the 
specific name was taken, is, however, only an exceptional character. 
The present species presents some analogy with P. macilenta; but the shell is 
narrower, the whorls more convex, more rounded on the shoulder, and more contracted 
in front; the canal is narrower, the outer lip more arched, and the sinus wider. 
Size.—Axis, 1 inch and 3-12ths; diameter, rather more than 4-12ths of an inch. 
Localities—Barton, Muddiford (Highcliff). Mr. Sowerby also gives Highgate, 
but I do not know of any specimen from that locality. The species is, apparently, 
confined to the upper beds of the middle eocene deposits, and is not common. 
No. 153. PLEUROTOMA FUsIFORMIS, Sowerby. Tab. XXVII, fig. 1a, 6. 
PLEUROTOMA FUSIFORMIS, Sow. 1823. Min. Con., vol. iv, p. 119, t. 387, fig. 1. 
— — Morris. 1843. Cat. Brit. Foss., p. 157. 
Non PLEUROTOMA FUSIFORMIS, Sow. 1831. Trans. Geol. Soc., 2d series, vol. iii, p. 418, t. 39, 
fig. 20. 
P. testé elongata, fusiformi, angustd, subturritd, longitudinaliter costatd, spiraliter 
fasciatd: spird elevatd, acuminata: anfractibis angulatis ; ultimo anfractu antice sensim 
attenuato, in canali longo, lato, terminanti ; marginibus posticis concentrice tenuiter lineatis, 
pauxillulum cavatis; costis rotundatis, ultimo anfractu evanescentibus ; fasciis spiralibus 
numerosis, wregularibus, tnequalibus, lineis incrementi scabratis: aperturd lanceolata ; 
labro arcuato ; sinu lato, sub-profundo, in margine collocato. 
Shell elongated, narrow, fusiform, longitudinally ribbed, and spirally banded: the 
spire, which, in the larger specimen figured, consists of eight volutions exclusive of 
the pullus, is elevated, forming nearly two fifth parts of the whole length of the shell. 
The whorls are sharply angulated at the shoulders, giving a turreted appearance to 
the spire; the posterior margins are moderately wide, slightly depressed, a little 
thickened and crenulated round the suture, and ornamented with fine, concentric, 
raised lines, two or three of which, immediately behind the shoulder, are stronger than 
the rest, and granulated by the lines of growth of the smus; the longitudinal ribs are 
rather numerous, rounded, and extend to the middle of the whorls, but become obso- 
lete on the body-whorl of the adult shell; the spiral bands over the middle and front 
parts of the whorls are numerous, unequal, irregular, becoming more distant on the 
canal, where occasionally fine, thread-like lines rise between them; the bands are 
