82 JOURNAL OF CONCMOI.OGY, VOL. l6, NO. 3, JANUARY, I92O. 



If }'ou examine the full-grown shell of H. pouiatla you may have 

 noticed that the growth is often very irregular, through the mouth 

 having been damaged before maturity. This I think is caused by 

 this species being very timid and easily frightened. It readily drops 

 off the bush or tree, or even rolls down a steep bank, and the animal 

 being heavy causes the edge of the mouth to be damaged. 



Habitat has a very considerable influence on the size of a shell. I 

 have noticed this most in the west of Ireland. The H. nemoralis on 

 Inishmurray were very large — the largest Irish specimens I have 

 taken, but rather thin, although the island is purely limestone ; but 

 on the mainland opposite at Streedagh Point they were quite small but 

 much thicker and stronger shells. H. itala, however, is the species 

 that I found to vary most in size ; very large from Mungret near 

 Limerick, and very small ones, but full-grown, from Loonah Point, 

 Co. Mayo, and from Salthill, a suburb of Galway, where they were in 

 large quantities on a grassy bank without any cover. 



The mark on land shells showing where the specimen stopped 

 growing previous to hibernation is generally easily seen, but this is 

 not so often noticed in freshwater shells ; but where you find a 

 thickening, as on L. stagnalis var. variegata, showing a repetition of 

 white marks or ribs, it is caused mlainly through drought during the 

 growth period. Occasionally shells are found that vary much in 

 colour after hibernation, and I have collected at Manorbier a full- 

 grown H. hortensis which commenced a pure white, but after hiber- 

 nation completed the shell with the ordinary yellow colour. 



Pairing of two distinct species has occasionally been noticed, as of 

 H. iienwraUs and H. hortensis^ but I have one specimen that I took 

 at Bundoran which I think is a cross between H. nemoralis and H. 

 iiala, as it has the distinct five bands of II. nemoralis, but the wide 

 open umbilicus of H. itala., and is much flatter than the ordinary 

 II. tiemoralis. In some places I have found large quantities of shells 

 of II. nemoralis recently dead, but quite cleaned out, especially once 

 when I was staying in Monsal Dale, and this I think was caused by 

 glow-worms, as I saw many of these, late at night, on the bank where 

 the dead shells were to be found. 



Some species of land and freshwater shells are found at very high 

 altitudes. I ha\e myself collected at Arolla, at over 7,000 feet, and 

 above the zone of the jioted Arolla pine, Pyramidula rupestris, P. 

 ruderata, and Encomihis Jnlvics. Also near Arolla, at 7,500 feet, 

 H. arbustornm var. alpicola. The snow very seldom nielts there 

 before the end of June, and I collected the shells in July, when the 

 whole mountain side was covered with a luxuriant growth of wild 

 flowers. Land shells have, however, been found in the Andes up to 



