18 



MOLLUSCA. 



[Teachelipoda. 



Found plentifully at Falmouth, Cornwall ; Salcomb Bay, Devonshire ; 

 Donaghadee and Portmarnock, Ireland. 



In a young state, this shell is often of an uniform, light-brown colour, 

 with close-set, longitudinal striae between the ridges j and the base fur- 

 nished with a siibcarinated edge, above which the sulcus is crenated. 



2. T. umbilicatut, pi. XI, f. 9 and 1 1 First Ed., pi. 45, f.9and 1 1 : Mon- 

 tagu, p. 286 ; Da Costa, p. 46, pi. 3, f. 4, 4 ; Fleming, lirit. An., p. 822 ; 

 Brown, Ency. Edinensis, pi. 54, f. 8; lb. Ency. Brit., VI, p. 450; Tro- 

 ehtu umbilicarh, Pennant, Brit. Zool., IV, p. 126, pi. 80, f. 106; Lamarck, 

 VII, p. 28 ; Trochus cinerarias, Donovan, Brit. Sli., Ill, pi. 74, three cen- 

 tral figures; Turton, Brit. Fati., 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 stria;, 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 foci near low-watermark, in Devonshire; Wales; and is 

 plentiful in the Kyles of Bute; Portmarnock, Dublin Bay, and Killough, 

 Ireland. 



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. T. cineraria*, pi. XI, f. 5 and 8. — First Ed., pi. 45, f.5and8; Mon- 

 tagu, p. 284; Donovan, lirit. Sh., Ill, pi. 74, two upper and two lower 

 figures; Fleming, Brit. An., p. 322; Lamarck, VII, p. 29. 



Shell subconic, subdepresscd, 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 striae, diagonally crossed by very 

 fine, nearly obsolete, longitudinal stria;; 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 cinerarias, 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.lillnralis, pi. XI, f. 1 and 4.— First Ed., pi. 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 stria;, intersected by almost in- 

 visible, obliquely longitudinal, very close stria;; 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 ieflected over the umbilicus, which is rather 

 small, a little compressed, and penetrating to the apex ; colour yellowish 

 ash, or pah' reddish-buff; with fine, irregular, obliquely. longitudinal lines 

 ol deep reddish-brown. Ordinary diameter at the base half an inch ; 

 height somewhat more. The specimen from which our figure was taken 

 measured six-eighths 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 cinerarias; but will be at once recognised by its perforated apex, 

 in the umbilicus being smaller and slightly compressed, in (he Stria 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 Day, west coast of 

 Ireland. 



5. T. perforata!. 



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 stria;; 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 five- 

 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 Trochus cinerarias, 

 but, on closer examination, we found it to possess very different charac- 

 ters. It differs from all the other British Trochusidae in its being invested 

 by a very 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 Trochus umbilicatus. It is considerably more de- 

 pressed than T. litloralis. 



6. T. tumidus, pi. XI, f. 5 and 8 First Ed., pi. 45, f. 5 and 8; Mon- 

 tagu, p. 280, pi. 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 striae; 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, pi. XI, f. 30 and 31 First Ed., pi. 51, f. 16, 17. 



Trochus rugosus, Brown, Wcrnerian Mem., II, p. 520, pi. 24, f. 5; Helix 



subcarinata, Montagu, p. 438, pi. 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, which is 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 arc 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 stria', 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, BigberryBay. and Milton Sands, Devonshire; 

 the south coast of Kent; and in drifted sand, Portmarnock, Ireland. It 

 is a rare British shell. 



Subdivision II. — Destitute of on Umbilicus. 



8. T. y.ki/phinus, pi. XI, f. 1C, 17, 18, 19, 21, 22, 24, and 29.— First 

 Ed., pi. 45, f. 10, 17, 18, 19, 21, 22, 24, and 29; Pennant, Brit. Zool., 

 IV, p. L26, pi. 80, f. 103; Donovan, Brit. Sh., II.pl. 52; Montagu, p 

 274; Turton, Brit. Faun., p. 177; Fleming, Brit. An., p. 823; Brown, 

 Ency. Brit., VI, p. 452; lb. Ency. Edin., II, p. 553, pi. 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 volution is broader, and more promi- 



