Journal of conchology . e cecological features along a variety of different lines ; this pre-liminary enquiry enables one, however, to limit such an investigationwithin practical bounds and examine a few loci, say H, C, and E, inelaborate detail. Note, too, that these tentative conclusions as to the 1 By open I mean open to the sun, by open to the wind and weather. 2 In all the loci the substratum is the same sort of stone wall, and the only differences notedwere in its surroundings. 3 Perhaps because of the dust which gets the mineral matter into a more readily solubleslate for plant
Journal of conchology . e cecological features along a variety of different lines ; this pre-liminary enquiry enables one, however, to limit such an investigationwithin practical bounds and examine a few loci, say H, C, and E, inelaborate detail. Note, too, that these tentative conclusions as to the 1 By open I mean open to the sun, by open to the wind and weather. 2 In all the loci the substratum is the same sort of stone wall, and the only differences notedwere in its surroundings. 3 Perhaps because of the dust which gets the mineral matter into a more readily solubleslate for plants and animals icf. Science Gossip, vol. iv (1898), p. 343). JOURNAL OF CONCrtOLOGY, VOL. l6, NO. 1, JANUARY, I9I9. relation between size and habitat are likely true only of the neigh-bourhood of Portmadoc; the influence of shading and exposure isprima facie related to the prevailing climatological conditions, andwhat produces grateful dampness in Kent may give us a horrid bogin North Wales. c- i, •? il« .•G ^. 1 mile Fig. I.—Map showing the loci : the Glaslyn river and the 500 feetcontour are also indicated. BOYCOlT : , VARIATION OK BIDENlATA. 23 ;; 1;: z[. rp m ;e :: :: :: ::: o a$ 90 95 100 TO 5 no 115 120 125 13 ( Altitude Fig. 2.—Diagram of the distribution of the altitudes of the shells fromloci E (lined) and H (dotted), both expressed as if the totalwere 100. Fig. 3.—Diagram of the mean altitudes and diameters of the shells fromthe different loci. Litnnaea glabra Miiller at Caldon Low, Staffs.—In March of this yearZ. glabra was found in great numl)ers in a small grass-choked ditch, about eightyards long by two feet wide, very close to the south edge of the limestone of whichthe Weaver Hills ridge consists. The ditch is practically eleven hundred feet abovesea-level. The only other species noticed was Pisidittm personatum Malm. Onthe occasion of a second visit in June the ditch was quite dry, but L. glabra wasstill present and very c
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