18 MOLLUSCA. 
Found plentifully at Falmouth, Cornwall; Saleomb Bay, Devonshire ; 
Donaghadee and Portmarnock, Ireland. 
In a young state, this shell is often of an uniform, light-brown colour, 
with close-set, longitudinal strize between the ridges; and the base fur- 
nished with a subcarinated edge, above which the sulcus is crenated. 
2. T. umbilicatus, pl. XI, f.9 and 11.—Virst Ed., pl. 45, f.9and11: Mon- 
tagu, p. 286; Da Costa, p. 46, pl. 3, f. 4,4; Fleming, Brit. An., p. 322; 
Brown, Ency. Edinensis, pl. 54, f. 8; Ib. Ency. Brit., VI, p. 450; Tro- 
chus umbilicaris, Pennant, Brit. Zool., IV, p. 126, pl. 80, f. 106; Lamarck, 
VII, p. 28; Trochus cinerarius, Donovan, Brit. Sh., III, pl. 74, three cen- 
tral figures; Turton, Brit. Fau., p. 178. 
Shell strong, subconic, depressed, with five nearly flat volutions, ter- 
minating in an obtuse apex, and defined only by a fine, thread-like 
suture; base of the body rounded at the margin; the whole shell covered 
by almost obsolete spiral striae, which are stronger on the somewhat flat- 
tened base; aperture compressed and angulated; inside pearlaceous, re- 
flecting deep green and crimson; outer lip flattened on the edge; umbilicus 
large, white, rounded at its edges, slightly wrinkled internally, and pene- 
trating to the apex; colour white, livid, or greenish, with longitudinal, 
waved or zigzag, reddish-purple lines. Diameter at the base three quar- 
ters of an inch; height not quite so much. 
Found on fuci near low-water mark, in Devonshire; Wales; and is 
plentiful in the Kyles of Bute; Portmarnock, Dublin Bay, and Killough, 
Treland. 
Young shells of this species are greatly depressed, those of three-eighths 
of an inch at the base being hardly one-eighth high. The apex of the 
Trochus umbilicatus is so thinly covered with epidermis, that it is but rarely 
found perfect, the nacreous substance almost always being exhibited. The 
very highly iridescent reflections in the interior of the aperture is an uni- 
form character of this species. 
3. TZ. cinerarius, pl. XI, f. 5 and 8.—First Ed., pl. 45, f. 5and8; Mon- 
tagu, p. 284; Donovan, Brit. Sh., III, pl. 74, two upper and two lower 
figures; Fleming, Brit. An., p. 322; Lamarck, VII, p. 29. 
Shell subconic, subdepressed, not quite regularly toper, with five 
slightly-raised volutions, separated by a fine suture, terminating in a ra- 
ther small produced apex; the lower margin of the body subcarinated; 
the whole shell beset with strong spiral striz, diagonally crossed by very 
fine, nearly obsolete, longitudinal striz; colour cinereous, sometimes 
greenish-yellow, with fine, longitudinal, undulating, oblique, brown lines, 
frequently of a purplish hue; aperture angulated, internally pearlaceous ; 
umbilicus large, deep, and abruptly narrowed within. Size of the base 
one inch; height seven-eighths. Its height, however, is but seldom so 
much in proportion to its diameter, being generally only about six-eighths 
when its diameter is an inch. 
Common on most of the British shores, in pools, between high and low 
water-mark. 
Fig. 10. A variety of Trochus cinerarius, in which the volutions are 
more inflated, and the ground colour of a fine pale Indian yellow, with a 
series of deep burnt-umber brown, triangular spots on the upper margin of 
the body. 
4, T.littoralis, pl. XI, f. 1 and 4.First Ed., pl. 45, f. 1 and 4. 
Shell strong, conical, with six slightly rounded volutions, defined by a 
well-marked suture, terminating in a small, obtuse, perforated apex ; the 
whole shell covered by very strong, spiral strize, intersected by almost in- 
visible, obliquely longitudinal, very close striae; base of the body with a 
sharp subcarinated margin, slightly rounded beneath; aperture subquad- 
rangular, but somewhat rounded, pearlaceous within; outer lip thin at 
: the margin, and considerably sunk beneath the base of the shell; inner 
lip thickened, and slightly reflected over the umbilicus, which is rather 
small, a little compressed, and penetrating to the apex ; colour yellowish 
ash, or pale reddish-buff; with fine, irregular, obliquely longitudinal lines 
of deep reddish-brown. Ordinary diameter at the base half an inch; 
height somewhat more. The specimen from which our figure was taken 
measured six-elghths and a little more in height. It is in the Cabinet of 
Lady Jardine. 
This shell at first sight may be mistaken for a produced variety of 
Trochus cinerarius; but will be at once recognised by its perforated apex, 
in the umbilicus being smaller and slightly compressed, in the striz being 
stronger, and in its more rounded and less compressed aperture. 
We first discovered this species on the rocks at Killoch, county of 
Down, Ireland, and have since obtained it from Clew Bay, west coast of 
Ireland. 
[TRacHELIPoDA. 
5. T’. perforatus. 
Shell subconic, strong, with fine slightly-raised volutions, terminating 
in an obtuse, perforated apex; whole surface invested by a thick, papil- 
lose, shagreen-like epidermis, of a brownish-drab colour; beneath which 
the shell is covered with strong, smooth, spiral strize ; colour of a green- 
ish-ash; and ornamented by obliquely longitudinal fine reddish-brown 
lines. Base of the body subcarinated, and a little rounded beneath; aper- 
ture subquadrangular, pearly within; inner lip thickened, and slightly re- 
flected over the umbilicus, which is small, and penetrating to the apex. 
Diameter at the base nearly six-eighths of an inch; heighth about fiye- 
eighths. 
Dredged in deep water in the Kyles of Bute, by James Smith of Jordan- 
hill, Esq. 
This shell was at first mistaken by us for a variety of T’rochus cinerarius, 
but, on closer examination, we found it to possess very different charac- 
ters. It differs from all the other British Trochusidz in its being invested 
by avery thick epidermis; and its subcarinated form at the base, with the 
colour and character of its markings, and less intense by nacred reflections, 
distinguish it from the T’rochus umbilicatus. It is considerably more de- 
pressed than 7’, littoralis. 
6. T. tumidus, pl. XI, f. 5 and 8.—First Ed., pl. 45, f. 5 and 8; Mon- 
tagu, p. 280, pl. 10, f. 4, 4; Turton, Brit. Fau., p. 177; Fleming, Brit. 
An., p. 322. 
Shell strong, subconic, with five rather tumid volutions, separated by a 
deep, well-defined suture, and terminating in a small but not toper apex: 
the whole shell covered with extremely fine, close-set spiral strize; base 
of the body provided with a subcarinated belt, and somewhat rounded be- 
neath, with a small umbilicus, which frequently decreases with age, and 
in the larger shells is sometimes nearly closed; aperture subquadrangular, — 
pearlaceous within; colour generally cinereous brown, sometimes yel- 
lowish, and at others purplish brown; streaked with longitudinal, undu- 
lating, continuous lines; and generally having a bronze appearance, occa- 
sioned by the thinness of the outer coating, which allows the mother-of- 
pearl to shine through. Height seldom exceeding three-eighths of an inch; 
breadth somewhat more. 
Found in Salcomb Bay and Torcross, Devonshire; the Kentish coast; 
Weymouth; the coasts of Wales, estuary of the Clyde, and Firth of Forth; 
and Portmarnock and Dublin Bay, Ireland, of a large size. In this 
latter locality the specimen was found from which our figure was drawn. 
7. T. subcarinatus, pl. XI, f. 30 and 31.—First Ed., pl. 51, f. 16, 17. 
Trochus rugosus, Brown, Wernerian Mem., II, p. 520, pl. 24, f. 5; Helix 
subcarinata, Montagu, p. 438, pl. 7, f.9; Turton, Brit. Fau., p. 187. 
Shell subovate, subpellucid, milk-white; with four moderately elevated 
volutions, well defined by a hollow suture, below which is a spiral groove; _ 
body large, considerably inflated; spire small, the volutions of which are 
placed somewhat laterally ; on the slightly rounded base there are three 
concentric, elevated, smooth ridges, the innermost emanating from the 
umbilicus, whichis large and deep, and terminating behind the pillar lip; 
the outermost forms a zone around the margin of the base, the central 
ridge being nearly equidistant between the others; on the upper part of 
the body are two spiral ridges, the superior one running spirally to the 
middle of the second volution; the whole upper surface between the 
ridges is covered with very fine undulating, longitudinal striz, and which 
is divergent on the base, emanating from the umbilicus; aperture suborbi- 
cular; outer lip thick, considerably expanded; inner lip reflected, and 
spreading a little over the umbilicus. Diameter at the base not an eighth 
of an inch; height a little more than a sixteenth. It is a strong shell for 
its size. 
Found in Salcomb Bay, Bigberry Bay, and Milton Sands, Devonshire; 
the south coast of Kent; and in drifted sand, Portmarnock, Ireland. It 
is a rare British shell. 
Subdivision IT.—Destitute of an Umbilicus. 
8. T. Zizyphinus, pl. XI, f. 16, 17, 18, 19, 21, 22, 24, and 29.—First ~ 
Ed., pl. 45, f. 16, 17, 18, 19, 21, 22, 24, and 29; Pennant, Brit. Zool., 
IV, p. 126, pl. 80, f. 103; Donovan, Brit. Sh., Il, pl. 52; Montagu, p 
274; Turton, Brit. Faun., p. 177; Fleming, Brit. An., p. 523; Brown, 
Ency. Brit., VI, p. 452; Ib. Ency. Edin., II, p. 553, pl. 55, f. 8; La- 
marck, VII, p. 23. 
Shell conic, strong, with seven or eight flat volutions, gradually taper- 
ing to a very fine pointed apex; the whole shell covered by a series of 
spiral ridges; the lower one in each yolution is broader, and more promi- 

