NOTE ON HYDROBIA JENKINSI.
213
tion from abroad; but, until this is proved by the discovery of its
native habitat, we are compelled to admit it as a species indigenous
to this country.
There is a group of Hydrobia to which Stimpson gave the name
Potamopyrgos, which agrees very closely with this species as regards
the carinate character of the whorls. The species belonging to this
group occur in New Zealand and Tasmania, and one species,
H. legrandiana, bears a considerable resemblance to the present
species.
The foregoing has been kindly written at my request, by Mr.
Edgar Smith, as a permanent record of this new brackish-water
species in our county.
As the only published drawing of this mollusc (in "Science
Gossip") does not, in my opinion, convey a clear idea of its char-
acters, I have had the accompanying block made from some of my
drawings of the living animal with its shell and operculum, from
Beckton. The shell selected for illustration consists of six whorls.
Hydrobia jenkinsi (E. A. Smith), Beckton Marshes, Barking, Essex.
I exhibited a series of the Beckton Shells at our meeting at
Theydon Bois on the 17th May, 1890 (vide E. N., vol. iv. p. 128).
For some time after the discovery of this form I was of opinion
that it had been introduced into England in some raw product; in a
similar way to that of Planorbis dilatatus, which was brought in raw
cotton from the United States, and has since become abundant in
the canals and rivers around Manchester.
The jute works which were established near Barking some twenty
years ago are close on the Beckton Marshes, being divided only by