228 NOTES ON THE MOLLUSCA OF THE THAMES ESTUARY,
(Achatina) acicula attached to it. This confirms my idea that this
latter species certainly does exist, either upon the marshes or in their
immediate neighbourhood, although from its burrowing habits it has
hitherto been overlooked.5
[It may be useful to append the titles of some papers on Hydrobia and allied
forms of Mollusca of our Essex marshes, which have recently appeared :—
J. T. Marshall. "On Hydrobiae and Assimineae from the Thames Valley."—
"Journ. Conchology," vi. (1889), pp. 140-142.
Ibid. "Further Notes on the British Hydrobiae," l.c, pp. 224-225.
E. A. Smith. "Notes on British Hydrobiae, with description of a supposed
new species," l.c, pp. 142-145.
Ibid. "A reply to Mr. J. T. Marshall's 'Further Notes on British Hydrobiae,'"
l.c., pp. 244-246.
Ibid. "Note on Hydrobiae jenkinsi."—" Essex Nat.," vol. iv., pp. 212-213.
A. J. Jenkins. "Distribution and Habits of the British Hydrolase."—
"Science Gossip," 1890, pp. 103-106.
Ibid. "Note on H. jenkinsi."—"Science Gossip," 1891, pp. 184-185.
A. J. Jenkins and L. 0. Grocock. "Notes concerning the Distribution of
Mollusca in the Thames Estuary," l.c, 1891, pp. 8-10.
Walter Crouch. "Note on Hydrobia jenkinsi."—" Essex Nat.," vol. iv., pp.
213-214.
Ibid. "Hydrobia jenkinsi in Essex."—"Science Gossip," 1891, pp. 163-164.
J. W. Williams. "The New Hydrobia."—"Science Gossip," 1890, pp.
131-132.—Ed.]
LIST OF SPECIES.
I.—Fresh Water and Land Shells.
Order LAMELLIBRANCHIATA.
Family SPHAERIIDAE.
Sphaerium corneum, L. Fairly common; Plumstead and
Tilbury Marshes.
S. lacustre, Mull. Same localities, and Erith Marshes.
Pisidium fontinale, Drap. Local; Plumstead Marshes.
Order PECTINIBRANCHIATA.
Family PALUDLNLDAE.
Bythinia tentaculata, L. Common, and generally distributed.
Var. albida, Rim. One specimen from Coldharbour Marsh.
B. leachii, Shepp. Common in same locality as B. tentaculata.
5 See Essex Nat., vol. iv., p. 227, in report of meeting on December 2nd, 1800, when Mr. W.
Cole exhibited specimens of Coecilioides acicula from a human skull at East Tilbury. These
specimens appear to be recent shells, and, therefore, it is probable that C. acicula exists on the
Essex marshes, although its subterranean habits enable it, as Mr. Jenkins suggests, to escape
detection.—Ed.