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NOTE ON HYDROBIA JENKINSI.
By EDGAR A.SMITH, F.Z.S. (President of the Conchological Society).
[Read December 30th, 1890.]
CONSIDERABLE interest is attached to the discovery of any
species new to the British fauna, especially as regards land and
fresh-water shells. Our ponds and rivers have been so thoroughly
searched that the discovery of anything fresh is not anticipated.
The species about to be discussed was first of all brought to my
notice by Mr. Walter Crouch, who, in the early part of 1889, kindly
presented to the British Museum three specimens found in ditches
at Beckton. Later on in the same year other examples, collected
south of the Thames at Plumstead, were submitted to me for deter-
mination by Mr. A. J. Jenkins. Mr. J. T. Marshall, of Torquay,
was also engaged about this time with the identification of
specimens which had been sent to him by "various correspondents
during the last few years." He came to the conclusion that the
shells in question belonged to Jeffreys' var. ovata of Hydrobia ventrosa
and wrote some notes to the "Journal of Conchology" (vol. vi. pp.
140-142) expressing this opinion. In a paper (l.c. pp. 142-145),
following that by Mr. Marshall, I stated that I considered it belonged
to a new species which I proposed to call Hydrobia jenkinsi. At the
same time I gave descriptions of the animals of this species, also of
H. ventrosa and H. similis, and pointed out the peculiarities which
distinguish each. Some discussion has since taken place respecting
the validity of H. jenkinsi as a distinct species. Mr. Marshall
still questioned its distinctness, declining to accept, as specific, some
of the characters which I had pointed out. He has more recently had
an opportunity of studying the living animals of H. jenkinsi and
H. ventrosa, and has written to me stating that he is now fully in
accord with me respecting this species. A full account of it has
been given by Mr. Jenkins in "Science Gossip," for May, 1890, pp.
103-106, with descriptions and figures of both the animals and shells,
and also of H. ventrosa and H. jenkinsi.
The question suggests itself, how is it that so remarkable a species
has hitherto been overlooked ? It would be interesting to know if it
exists in any old collections, that is, in collections got together twenty
to fifty years ago. It is just possible it may be a modern introduc-