104. HULL SCIENTIFIC AND FIELD NATURALISTS’ CLUB. 
The isolated cattle pond on Saltend Common probably 
dates from the time of reclamation. The chalk sides and 
foundation by which it is raised above the surrounding level 
do not favour the growth of aquatic plants, but Lemna, Potamo- 
geton, and Callitviche manage to exist in spite of periodic 
cleaning out. There are a few beetles and two species of 
Crustacea. Mollusca are represented by the bivalves Spharium 
lacustve and Pisidium pulchellum, and the omnipresent L. peregra. 
Bivalves have been known to attach themselves to the legs of 
beetles and birds, so that it is probable that these two have 
been introduced in this way from the ditches further inland 
where both are abundant. As the pond is frequently visited 
by ducks and waders in search of food, no great increase in 
number of any individual species can be expected, though 
Sph. lacustve is firmly established. 
The larger bivalves are not numerous; Anodonta cygnea 
and anatina are found in Hornsea Mere, and the latter is 
common in the Burstwick and Keyingham drains, its lower 
limit being about two miles from the outfall, since below this 
the Humber water makes the drains so salt that Tedlina 
solidula may be found near the cloughs. ‘Though the Keying- 
ham drain runs close to the Kelsey ponds I have not found 
Anodonta in them, but it has migrated to the old brickpond at 
Hestholme, which is also near the drain and within half-a-mile 
of Kelsey. 
Viviparus, Unio, Ancylus, and Velletia are notable omissions. 
We have probably no locality suitable for the first two, while 
the streams are too muddy and not sufficiently rapid for 
Ancylus, but there is no reason why the lake limpet, Vedletia, 
should not occur, though as its structure and habit render it 
particularly liable to dispersal, our unsuccessful search may 
be regarded as proof of its non-existence in the district. I 
have taken several fruitless journeys in quest of Dyeissensta 
on the information of labourers who assured me that they had 
gathered ‘‘ mussels’”’ exactly like the edible mussel, but in 
every case they proved to be Anodonta—a fact which seems 
to indicate that the average countryman’s power of comparison 
is very limited. This species, brought with Baltic timber, 
has spread inland from Goole, Wisbech, and London, but 
not, as far as I can discover, from Hull or Lynn—probably 
because these two are so near the sea that the salt water in 
the docks kills it immediately. To verify this, frequent search 
should be made in the Alexandra Dock at Hull, which is 
filled with fresh water. 
