PROSOBRANCHIATA. 227 
state are tuberculated, or roundedly costellated ; the posterior margins are moderately 
wide, very little depressed, nearly straight, and almost smooth, or ornamented with 
concentric lines, so faint and slender as to be almost imperceptible without the aid of 
a magnifying glass; the last whorl is produced in front, and, diminishing very 
gradually, terminates in a long, nearly straight canal. The aperture is lanceolate; the 
outer lip thin, sharp edged, and much arched; and the sinus, which is very wide, and 
sub-trigonal in shape, is placed a little in front of the middle part of the margin. 
. The long, narrow, lanceolate form, and nearly conical spire of this Pleurotoma 
distinguish it from all its congeners. 
Size.—Axis, | inch and 4-12ths ; diameter, 4-12ths of an inch. 
Localities.—Barton and Alum Bay (No. 29, Prestwich), where it is not very 
common. 
No. 152. PLEUROTOMA L&VIGATA, Sowerby. Tab. XXVI, fig. 9 a, 4. 
PLevROTOMA LHviGata, Sow. 1823. Min. Con., vol. iv, p. 120, t. 387, fig. 3. 
— _: Morris. 1843. Cat. Brit. Foss., p. 157. 
— — D’ Orb. 1850. Prod. de Paleont., vol. ii, p. 359, No. 412. 
Nec Prevrotoma LmviGcaTuM, Phil. 1836. Enum. Moll. Sic., vol. i, p. 199, t. 11, fig. 17. 
nec — LHVIGATA, De Kon. 1837. Coq. foss. de Basele, &c., p.27, No. 27, t. 1, fig. 5. 
nec — _ Mellev. 1843. Mém. sur les sables infer., &c., de Paris, p. 63, 
t. 8, figs. 9—11. 
P. testa elongato-fusiformi, angustd, turritd, transversim tenuissime lineata: spird 
elevatd, acuminaté: anfractibus convexis, antice subito coarctatis, prioribus oblique costel- 
latis ; marginibus posticis angustis, depressis, sub-canaliculatis, levibus ; ultimo anfractu 
an canalt longo, angusto, terminanti: apertura oblonga, ovata ; labro valde arcuato, tenui ; 
sinu lato, fere semicirculart, in margine collocato. 
Shell long, narrow, fusiform, turreted, costellated, and spirally lined: the spire 
elevated, pomted, terminating in a pullus of two round, smooth volutions; whorls 
convex, rounded on the shoulders, contracted rather suddenly in front; the posterior 
margins narrow, depressed, slightly hollowed out, having the sutural edges thin and 
quite simple, and the surface smooth, almost polished, presenting only very feeble lines 
of growth of the sinus. The ribs are distant, rounded, oblique, and extend almost to 
the front part of the whorl in the young shell, but become shorter and less prominent 
as the shell enlarges, and altogether disappear on the body-whorl of the fully formed 
shell; the spiral lines are very slender, sharp, but little elevated, irregular, unequal, 
and decussated by the lines of growth. The aperture is of an oblong, ovate form, and 
terminates in front in a long, narrow, and slightly curved canal; the outer lip is much 
