VERTIGO ANTIVERTIGO— EFFECT OF PROLONGED DROUGHT. 28 1 



rushes cut off close to the ground and posted to me by the Hon. R. E. Dillon, from 

 drier ground at Clonbrock, East Galway,a few days later. V. antivertigo, V. edmtida, 

 and Hyalinia nitida also occurred sparingly, with a dozen or so fine specimens of 

 Succinea elegans. That portion of the marsh at Shaw's Bridge which we visited is 

 over an acre in extent, and there must be tens of thousands of V. antivertigo 

 in a limited area there. This may help to explain where the great numbers 

 of V. angustior, V. pygmcea, and V. pusilla come from that we find dead in 

 "Pockets" in our northern sandhills in Ulster, especially those which have a good 

 area of marshy ground adjoining, with a variety of food-plants. At Portstewart 

 (especially where the dunes are fringed on one side by the swampy margin of the 

 Bann) thousands of the three species mentioned may be sifted out of a small bagful of 

 shell debris, collected at the proper place. I know three other localities for V. anti- 

 vertigo in Co. Down, at two of these only a few specimens, up to a dozen, are to be 

 obtained in an hour's careful collecting, but at the third, which is on the margin of 

 a flax-dam, I have taken thirty to forty under stones, in company with larger 

 numbers of V. pygmcea and Hyalinia nitida. — R. Welch {Read before the Society, 

 April 1 2th, 1899). 



Effect of Prolonged Drought on the occurrence of Land Mollusca.— Have 



any conchologists noticed the effect which was produced on land molluscs by the exces- 

 sive and protracted heat of August and September, 1898 ? I was in East Kent for 

 the first fortnight of September and found it most difficult to discover Helix nemoralis 

 or H. aspersa where I know they abounded. The latter was mainly sestivating in 

 the roots of hedgerow trees. On one of the hottest days I visited a down which 

 usually swarms with H. virgata and nearly all its varieties (/ ucozona, a'ba, hyalo- 

 zonata, ep'zona,a.nd hypozonn), but hardly one was to be seen except a very few on the 

 trunks of trees. In fact the only shells in this hitherto most productive place were 

 a few H. raniiana, and one H. ca'lusiana var. mino<-. H virgata is less affected by 

 the heat than any other shell, and I was puzzled, especially as the down was exactly 

 in the same condition as before, and I had visited it on hot days in the same month 

 in previous years. Seeing nothing to account for a wholesale mortality, I ascribed 

 the barrenness of the land to our tropical weather. But half-a-mile off, on the road 

 to Adisham, I found H. virgata in millions on an equally exposed and burnt up field. 

 In one place they so swarmed that a couple of dozen could be taken off any dry stalk 

 about a foot high, and the field looked as if it had an undergrowth of some white- 

 blossomed flower, so thick were the shells and so much did var. albida predominate. 

 Walking along the road I noted : — (1) That where H. virga a swarmed specimens 

 were uniformly very small. (2) That they were mostly var. albida (not alba). Excess 

 of numbers had dwarfed the race and deprived it of most of its pigment-producing 

 power. I had not noticed these points (especially the latter) so markedly elsewhere 

 before. (3) Farther along the road the numbers gradually diminished even almost 

 to disappearance, and pari passu did the size increase until at last the few found were 

 abnormally large, while nearly all were of the typical form or the var. subdeleta. 

 One or two other notes may be of interest : — ( 1 ) The colony of Turriciila terrestris is 

 flourishing, but year after year I find hardly any evidence of its extending its territory 

 even by a yard or two. (2) The locality for 17. arbustorum var. canigonensis (the 

 only one I know) yielded some specimens, but it had been made somewhat of a dust- 

 heap to the detriment of molluscan life. (3) The H. cartitsiana mentioned above 

 contained many eggs. Is not this late in the year? The eggs were also very large 

 for the size of the animal considering that it was very definitely var. minor. — • 

 J. W. Horsley, St. Peter's Rectory, Walworth {Read before the. Society , April 12th, 

 1899). 



