opinion that they were distinct: the British shell is more slender and spindle-shaped than the French; they are, perhaps, only local varieties; but it is extremely difficult to define the species of this genus.

This species was first described as British by Montagu.

80. 3. CLAUSILIA Rolphii.

Rolph's Close Shell. (t. 5. f. 54.) Shell ventricose, thin, opake, redbrown, with regular crowded raised striæ; aperture with four or five plaits, two of which are longer.

Clausilia Iphigenia Rolphii. Gray, Med. Repos.

1821. 182.

Clausilia Rolphii. Leach, MSS.; Gray, Ann. Phil. 15.; Férussac, Journ. Phys. 1820. 301.; Leach, Mollusc. ined. p. 119.; Alder, Mag. Zool. and Bot. ii. 111.; Turton, Man. ed. 1. 71. f. 54. Clausilia plicatula. Drap. p. 74. t. 4. f. 17, 18. ?; Brard, p. 85. t. 3. f. 10. ?; Jeffreys, Linn. Trans. xvi. 353.; Rossm. Icon. p. 39. t. 2. f. 32.

In damp places in woods, among the moss and stones, under nettles and dogs' mercury, and on trunks of trees, on a chalky soil.

Animal grey.

Shell an inch long, of a greyish brown horn-colour, tumid in the middle; spire composed of ten or eleven rather swollen volutions, which are marked with regular raised longitudinal lines; aperture roundishoval, sinuous at the upper and outer angle; the margin thick, white, detached all round, with four or

five plaits, two of which are much longer than the

rest.

Férussac, in his list of British Shells (Journ. Phys. 1820. 301.), says this shell has no analogy with any of Draparnaud's; and Mr. Alder observes that it is distinct from Clausilia plicatula Drap., to which it has been referred.

The species was first discovered by Mr. Rolph in Charlton Wood, Kent. It was first indicated as British by Férussac, and then by myself. I have since, at two distant periods, found it in the same locality, and I have seen specimens from Hastings, Sussex.

Like other species, it is sometimes found transparent and colourless. Dr. Turton indicates three varieties in the teething, but it is very variable in this respect.

81. 4. CLAUSILIA dubia. Doubtful Close Shell. (tx. f. 143.) Shell dark brown, rather ventricose, with strong raised striæ, rendered somewhat granular by a few spiral ridges on the lower whorls; whorls ten or twelve, a little rounded; aperture with two teeth on the pillar, the lower one forked internally; peristome whole, detached, and reflexed.

Clausilia dubia. Drap.; Alder, Cat. Supp. 1. c. 3.
Mag. Zool. & Bot. ii. 111.

Clausilia rugosa, var. Alder, Cat. 1. c. 32.

Fér.

similis. Gilbertson, MSS. B. M.; not

Inhab. rocks under moss - North of England.
This shell is about 5-8ths of an inch long, and

1-8th broad.

Mr. Alder, who first introduced this shell into the Fauna, observes, that it is undoubtedly the C. dubia of continental authors. It may be distinguished from C. rugosa by its greater size and ventricosity.

82. 5. CLAUSILIA nigricans. Dark Close Shell. (t. 5. f. 58.) Shell slender, sub-opake, blackbrown, with fine raised somewhat granular striæ; aperture with three plaits, the margin white and detached all round.

Helix perversa. Müller, Verm. 118.
Bulimus perversus. Brug.

Clausilia rugosa. Drap. p. 73. t. 4. f. 19, 20.;
Leach, Mollusc. p. 121.

Turbo bidens. Montagu, p. 357. t. 11. f. 7.

nigricans. Dillw. 375.; Pult. Dorset. 46.;

Turt. Dict. 225.

Turbo perversus. Penn. Brit. Zool. iv. t. 82. f. 116. Clausilia nigricans. Jeffreys, Linn. Trans. xvi.

351.

Odostomia nigricans. Flem. Ed. Ency.

Clausilia perversa.

perversa. Flem.

Var. 1. smaller, more slender.

Clausilia parvula. Leach, MSS. B. M.; Turton,
Zool. Journ. ii. 556., Man. ed. 1. 74. f. 58.';
Jeffreys, Linn. Trans. xvi. 352.; not Studer.
Var. 2. shorter, fewer whorls.

Clausilia Everettii. Miller, Ann. Phil. n. s. xix.
377.

Common under stones and in old walls.
Animal brown, corrugated, foot narrow.

L

Shell about half an inch long, glossy black or grey, often marked with short cinereous streaks, with regular raised lines, which, when closely examined, appear a little granular; spire composed of from seven to ten rather raised volutions; aperture oval, with the inner lip a little contracted, with three plaits, all on the pillar, the lower one interior and hardly distinguishable in the full-grown shell; the margin thick and white, but not reflected, detached all round.

This very common species varies greatly in size, in the slenderness and ventricoseness of the shell, and in the strength or slightness of the concentric striæ, but in a large series all these varieties gradually and uninterruptedly pass into one another, and they may all be found in specimens collected from the same locality. It is also rarely found transparent and colourless. Mr. Jeffreys describes a distorted specimen, with a prominent medial ridge down the whorls.

Mr. Alder has kindly communicated to me "a specimen of the shell he sent to Dr. Turton, which Dr. Turton calls C. parvula (t. 5. f. 59.); and also the specimens of the true C. parvula (according to Férussac), found in Germany, for comparison." He further observes, that all the British specimens he has seen, he thinks, are only varieties of C. nigricans, which, I think, the specimen fully bears out.

B. THE AQUATIC FREE-AIR-BREATHING MOLLUSCA have two contractile, compressed tentacles, with the eyes sessile, near their base; the head is contractile ; they are not provided with any operculum. They are all aquatic, and the British species are divided into two families. (See p. 101.)