22S 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. 1 a, b. 



Pleurotoma fusifokmis, 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. testa elongatd, fusiformi, angustd, subturritd, longitudinaliter costatd, spiraliter 

 fasciatd: spird elevatd, acuminata: anfractibus angulatis ; ultimo anfractu antice sensim 

 attenuato, in canali longo, lato, terminanti ; marginibus posticis concentrice tenuiter lineatis, 

 pauxillulum cavatis ; cost is rotunclatis, tdtimo anfractu evanescentibus ; fasciis spiralibus 

 numerosis, irregidaribus, inaqualibus, lineis incrementi scabratis : aperturd lanceolatd ; 

 labro arcuato ; sinu lato, sub-prof undo, 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 sinus ; 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 



