66 
MOLLUSCA. 
Cerithium. 
strongly striated to the base of the body; outer lip wing-shaped, 
and nearly semicircular; aperture elongated, and oblique; inner 
lip narrowly reflected on the columella. 
Found in the London Clay at Hordwell. 
11. P. laevigata.— The Smooth Pleurotoma, pi. XXXVII. 
fig. 8, 9* 
Pleurotoma Icevigata . Sowerby, Min. Conch. IV. p. 120, 
pi. 387, fig. 3. Fleming, Brit. An. p. 355. 
Elongated, turreted, almost smooth; body and spire nearly 
of equal length ; spire consisting of seven ventricose volutions, 
a little concave above, well defined by the suture, and provided 
with rather flattened, longitudinal ribs; a few obscure spiral 
stria? invest the shell, and some nearly obsolete lines of growth; 
aperture oblong-ovate, pointed above, and ending below in a 
short, almost straight, narrow canal, which with the aperture is 
nearly equal to the spire in length. 
Found in the London Clay at Muddiford and Highgate Ilill, 
London, 
Genus XXVI.—CERITHIUM.— Brucjuiere. 
Shell greatly lengthened, turreted; with numerous 
volutions; more or less tubercular, or spinous, or rough, 
in a very few instances smooth, or spirally grooved; 
aperture subquadrate or ovate, its upper part modified 
within by the abdominal region of the body; the outer 
lip or peritreme a little thickened, and sometimes broadly 
reflected, with a groove at its upper extremity; columella 
arcuated, with a sharp spiral plait at its base, and form¬ 
ing the upper margin of the canal, which is somewhat 
short, truncated, and generally reflected; aperture closed 
by a small horny operculum. 
1. C. cornucopia. —The Horn of Plenty Cerithium, pi. 
XXXVII. fig. 17. 
Cerithium cornucopuv. Sowerby, Min. Conch. II. p. 197? 
pi. 188, fig. 1, 3, and 4. Terebra cornucopia ?, Fleming, Brit. 
An. p. 347. 
Subulate, turreted, punctated; with upwards of thirty vari¬ 
ously ornamented volutions, terminating in a rather acute apex; 
volutions contiguous to the apex, with one crenulated keel, 
situated a little under the centre; in those immediately suc¬ 
ceeding, the margin imperceptibly assumes a tuberculated 
appearance, and a small knobbed carina rises between it and 
the middle one, with its lower edge crenulated; the tubercles 
on the upper margin gradually increase, the central keel 
becomes more depressed, while other carinae arise on each side 
of it in the central volutions, tuberculated above, undulated 
below with four or five transverse furrows; these carinae 
become broader, and the intermediate spaces assume the form 
of furrows, while the crenulations anil tubercles continue in 
an undulating series, those on the upper edge being elongated, 
and towards the interior portion of the shell unite with the 
undulations under them, and gradually supercede the furrows; 
from this point they by degrees recede from the margins, 
and on the two or three lower volutions, as well as the body, 
assume the form of oblong, obtuse, somewhat oblique knobs, 
nine or ten in number; whole surface covered by minute 
punctures disposed in lines, which diverge as they pass over the 
tubercles, and converge as they descend; aperture quadrate, 
terminating in a short, narrow, curved canal, its edge rising on 
the columella in the form of a plait; outer lip semicircular; 
columella with three strong, oblique plaits, and frequently pro¬ 
vided with a ridge above, on the base of the body. 
This shell is subject to great variety of aspect in its progress 
from the young to the adult condition, and varies in length and 
breadth in the 'full grown shell. It frequently exceeds a foot in 
length, the diameter of the body being one-fourth the length of the 
shell. 
Found in the London Clay, mixed with Green Sand, under 
Stubbington Cliff. 
2. C. giganteum. —The Gigantic Cerithium, pi. XXXVII. 
fig. 18. 
Cerithium giganteum, Lamarck, Env. de Paris, p. 95. 
Knorr, III. pi. 107, fig- L Parkinson, Organic Rem. III. p. 
71. Sowerby, Min. Conch. II. p. 199, pi. 18S, fig. 2. Terebra 
gigantea , Fleming, Brit. An. p. 347. 
Subulate; body short; spire very long, gradually tapering, 
consisting of numerous, fluted, minutely punctured volutions, 
which are separated by a shallow and narrow suture; superior 
portion of the volutions slightly nodulous, below which are 
six or seven equidistant, nearly obsolete transverse striae; aper¬ 
ture ovate, contracted above and below, columella having four 
plaits. 
This shell is said to attain the extraordinary length of thirty 
inches, while the diameter of the body volution is seven and a half 
inches. 
3. C. geminatum —The Gemmed Cerithium, pi. XXXVII. 
fig. 22, 23. 
Cerithium gemminatum, Sowerby, Min. Conch. II. p. 63, 
pi. 127, fig. 2, 2. Fleming, Brit. An. p. 357- 
Elongated, turreted, conical, smooth; body and spire of 
nearly equal length; the latter consisting of ten or eleven 
turreted volutions, terminating in an acute apex; each volution 
provided with seven or eight pairs of longitudinally disposed 
tubercles, the upper pair the largest, particularly on the body 
volution, where it is frequently bifid; the body is also furnished 
with two rows of very small tubercles; two nearly obsolete, 
transverse carinae uniting one pair of tubercles to the succeed¬ 
ing ones; aperture nearly orbicular, terminating in a slightly 
recurved canal; outer lip even; inner lip pretty broadly reflect¬ 
ed on the columella. 
Found in the London Clay at Barton Cliff. 
4. C. funatum. —The Corded Cerithium, pi. XXXVII. 
fig. 15, 16. 
Cerithium funatum, Sowerby, Min. Conch. II. p. 64, pi. 
128. Fleming, Brit. An. p. 358. 
Conical, elongated, tapering gradually to a somewhat pointed 
apex ; body about half the length of the spire, which consists 
of nine or ten volutions, each of which is furnished with two 
obtuse crenulated spiral ridges, thickened and tuberculate on 
their superior portion, which strongly resemble the twisting of 
a cord; body volution differing from the others, in being gar¬ 
nished with two additional transverse ridges; aperture some¬ 
what quadrangular, terminating in a slightly twisted, short 
canal; base smooth; outer lip even on the edge; pillar lip 
reflected on the columella, narrowed at its connexion with the 
body, and widening towards the centre. 
