88 
28. P. biserrata. —The Doubly-serrated Plcurotomaria, 
pi. XL. fig. 35. 
Plcurotomaria biscrrata . Phillips, Geo. of Yorkshire, II. 
p. 228, pi. 15, fig. 29. 
Shell acutely conical; body not quite so long as the spire; 
suture of the spire, and lower angle of the volutions, provided 
with a doubly serrated carina, and between them a crenulated 
line; base provided with three concentric furrows; and the 
whole surface obliquely striate. 
Pound in the Mountain Limestone, Derbyshire. 
29. P. tornatilis. —The Turned Plcurotomaria, pi. XL. 
fig. 36. 
Pleurotomaria tornatilis . Phillips, Geo. of Yorkshire, II. 
p. 228, pi. 15, fig. 25. 
Shell ovate; body large, inflated; spire small, consisting of 
four ventricose volutions; base somewhat pointed, and acute; 
body invested by a very broad, spiral, mesial hand, with a fur¬ 
row on each side, continued around the base of the volutions 
of the spire; base provided with two concentric furrows; the 
whole surface covered with distinct, spiral striae. 
Pound in the Mountain Limestone, Bolland. 
30. P. squamula. — The Scaly Pleurotomaria, pi. XL. 
fig. 37. 
Pleurotomaria squamula . Phillips, Geo. of Yorkshire, II. 
P . 227, ph 15, fig. 17. 
Shell regularly conical; body and spire of nearly equal 
length; sides almost flat; spire consisting of five volutions; 
whole surface covered with numerous, squamous, oblique ribs, 
either entire or bifurcate, or alternately long and short. 
Pound in the Mountain Limestone, Bolland. 
31. P. cirriformis. —The Cirrus-shaped Pleurotomaria, 
pi. XL. fig. 38 and 42. 
Helix? cirriformis . Sowerby, Min. Conch. II. p. 1 GO, pi. 
171, fig. 2. 
Shell conical, ventricose; volutions a little tabulate above; 
aperture nearly circular; a broad, raised, mesial band traverses 
the centre of the body and volutions of the spire, and is crossed 
by arcuated striae; whole surface covered with longitudinal and 
spiral, distinct, small, arcuated striae; base with a narrow um¬ 
bilicus. 
Found in the Mountain Limestone of Derbyshire. 
32. P. excavata. —The Excavated Pleurotomaria, pi. XL. 
fig. 39. 
Pleurotomaria excavata . Phillips, Geo. of Yorkshire, II. 
p. 228, pi. 15, fig. 20. 
Shell conical; the volutions tumid, and provided with a sharp 
carina on their sides; almost plain above and below; umbilicus 
closed. 
Found in the Mountain Limestone at Bolland. 
33. P. fusiformis. — I he Spindle-shaped Pleurotomaria, 
pi. XL. fig. 40. 
Pleurotomaria fusiformis. Phillips, Geo. of Yorkshire, II. 
p. 227, ph 15, Jig. 16. 
Shell smooth, fusiform ; spire not quite so long as the body; 
sides of the volutions rather flat, and furnished with three spiral 
carina?, the lower one sutural; aperture ovate. 
Pound in the Mountain Limestone, Bolland. 
34. P. serrilimba. —The Tooth-bordered Pleurotomaria, 
pi. XL. fig. 41. 
Natica. 
Pleurotomaria serrilimba . Phillips, Geo. of Yorkshire, II. 
p. 228. 
Shell acutely conical; body very short; spire long, with nearly 
flat sides; the band which traverses the lower margin, with a 
serrated margin. 
Found in the Mountain Limestone, Derbyshire. 
35. P. compressa —The Compressed Pleurotomaria, pi. 
XXXIII* fig. 16, 17. 
Helicina compressa. Sowerby, Min. Conch. II. p. 33, pi. 
10, three middle figures. 
Shell thick, strong, depressed; body large; spire short, con¬ 
sisting of three nearly flat-sided volutions; aperture subovate, a 
little angular above; body provided with an elevated, sharp, 
narrow, mesial band, which also invests the lower part of the 
volutions of the spire. 
Found in the Mountain Limestone of Leicestershire. 
Genus XLIL—SIGARETUS.— Lamarck. 
Shell subauriform, somewhat orbicular, and depressed, 
generally with a nearly marginal, hardly prominent spire, 
consisting of two or three volutions; aperture entire, 
longer than wide, greatly dilated, with its edges disunited 
at the upper extremity, and embracing the lower part of 
the body; inner lip short, spirally twisted, and for the 
most part a very little reflected above, but in some in¬ 
stances so much so, as to form a small umbilicus ; inside 
of the aperture exhibiting two muscular impressions, one 
at the upper, and the other at the lower extremity. 
1. S. canaliculatus —The Canaled Sigaretus, pi. XLIII. 
fig. 16, 17. 
Sigaretus canaliculatus. Sowerby, Min. Conch. IV. p. 115, 
pi. 384. 
Shell slightly ovale, convex; spire depressed, with two canali¬ 
culate volutions, terminating in a pointed apex; aperture sub- 
ovate, rounded below, and somewhat square next the columella, 
over which the inner lip is broadly reflected, with a large 
umbilicus behind; whole surface covered by longitudinal strire, 
which are decussated by transverse lines of growth. Length 
varying from half an inch to three-quarters. 
Pound in the London Clay at Hordwell. 
FAMILY V—NERITACEA. 
Shells inhabiting the sea and fresh waters; semi- 
globular, or oval in their form ; destitute of a columella; 
the margin of the inner lip sharp edged, and placed 
transversely; always provided with an operculum. 
Genus XLIII.—N AT IC A.— Adanson. 
Shell subglobose, oval, or oblong; umbilicate; spire 
short, sometimes very short, with apex very rarely 
pointed; aperture large, semicircular, and very seldom 
MOLLUSCA. 
