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HARDWICKE'S SCIENCE-GOSSIP. 



little higher up, where the stream is clear, and the 

 sliell-fish undisturbed. Observe the gaping ends of 

 the shell, and thus I push tiie end of this stout rod 

 between the partiuily-open valves ; now they close 

 upon the stick, and so we bring our prize holding 

 on to the stick to the bank. 



"You will recollect (addressing my companion) 

 that in the muddy pond we have just left we chiefly 

 got small bivalves and only a few snail shells. I 

 have already told you that water-shells differ much 

 in their habits, and that consequently our search 

 for any particular species, or set of species, can 

 only be successfully carried on when that know- 

 ledge is our guide. Those little bivalves, and a 

 few of the snails that we have gathered, habitually 

 live at the bottom, and will of coui-se be brought 

 up in the dredge when that implement is dragged 

 over it ; but there are many shells which live at or 

 near the surface, and which feed on the submerged 

 and floating plants. Therefore we must seek out 

 a weedy pool if we would increase the variety of 

 our collection." Such a one is reached. And the 

 dredge brought hito requisition, anon to snatch up 

 a floating snail, again to sweep it over and through 

 the plants, varying our occupation by dragging to 

 the margin the tangled masses of weeds ; by all of 

 which means a considerable number of the class 

 of air-breathing water-snails were obtained— ad- 

 monishing my young friend that this last plan 

 does very well when the plants grow in dense 

 m^ses, because when thus interlaced they form 

 a natural net to catch those snails which on the 

 slightest disturbance lose their hold upon 

 tlie weeds, and which would otherwise fall to the 

 bottom. 



Yet another plan remains to be pursued, one by 

 which the few small shells hiding among the roots 

 of the plants may be secured. Obviously the 

 dredge misses such; but by pulling up the plants 

 by their roots, and well shaking them in the half- 

 sunken sifter, we yet after all obtain them. 



From causes which need not be explained here, 

 the shells living in some ponds are all much 

 eroded, or coated with a ferruginous deposit ; it 

 win be desirable therefore to fiiid out the localities 

 where specimens arc in the best condition, so that 

 you may have typical specimens for comparison 

 before an extensive collection is made. 



Our experience is that though a considerable 

 number of species may be obtained from a ditch or 

 pond, yet a few are found as the sole molluscan 

 tenants of particular sheets of water ; that lakes 

 exliibit a dearth of life, and that the greatest 

 variety is often to be met with in canals ; but should 

 a search be carried on in them, avoid the tow- 

 path side, for reasons that a little thought will find 

 ready solution. 



Living near the sea, and within a short distance 

 of wooded hill-sides, \^ e had within a limited area 



such a variety of physical features that had led us to 

 infer the existence of a rich molluscan fauna for the 

 neighbourhood. Our second excursion was de- 

 voted to a search for snails along the sea margin 

 and shores of the estuary. Proceeding along the 

 low sand-dunes— at first sight a most uninteresting 

 spot — Helix cuperata, H. virgata, Bullyaus acutus, 

 and a few other snails, were found clustering upon 

 the low, stunted vegetation, in such numbers that 

 handfuls might have been gathered within an area 

 of a few square feet. Leaving the sea-shore, our 

 way led us over the fore-shore of the mouth of the 

 river, crushing under our feet at every step shells 

 of Cardlum edule, Scrohlcularla pipercUa, and a few 

 other bivalves which find a congenial habitat in 

 such situations. Gaining the .muddy margins of 

 the higher part of the estuary, Conovulm was looked 

 for, and found under the stones along the high- 

 water mark. Higher up the river the rejectanientum 

 on its banks was carefully turned over ; and we 

 were successful in securing a number of land shells. 

 The animals, of course, do not live in such places ; 

 but their empty shells, which only were found, had 

 been brought down from the land surface by the 

 agency of the streams and tributaries of the river. 

 Nevertheless such an omnmm (jatherum should 

 demand attention, as its contents give an insight 

 into the character of the land and freshwater forms 

 within the area of drainage of the river. 



The number of estuariue species which have a 

 place in our works devoted to British land and 

 freshwater snails is very few, and the majority, 

 moreover, are confined to the margins of the tidal 

 rivers in the South of England. ThM^AsslmiueaGray- 

 aiia, Ilijdrohla rcntrosa, and //. sliiillls, live on the 

 mud banks beneath the shade of sedges and rushes, 

 skirting the Thames below Greenwich. To gather 

 these small shells singly is a tedious operation ; but 

 if a thin piece of flat wood, or other substitute as 

 the ingenuity of the collector suggests, be used to 

 scrape lightly over the surface of mud, transfer- 

 ring the mass to the dredger, and washing in 

 water, a number of specimens sufiicieut to stock 

 every private cabinet in the country may be 

 obtained in a short space of time. 



Eor the third initiatory excursion our steps were 

 directed inland, and as we proceed the hedgerows, 

 mossy banks, and margins of water-courses were 

 diligently searched ; finding a Tlellx here, a Fupa 

 or a Succlnea there. Gaining the woods, we turn 

 over the damp leaves ; grub under the clumps of 

 ferns and wood-rushes for small Helices, Pupcc, and 

 the like ; scan the trunks of the trees, for the climb- 

 ing CJausUiir', BulLul, and Ildlces, not unmindfid 

 that each little dirt-like mass is probably a \Buli- 

 mus obsciirus, which, by covering its shell with 

 mud, thus exhibits a protective faculty, and often 

 escapes detection. Kaise the rotting bark for 

 Baled ; lift the stones at our feet, or roll away a 



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