{23 50 Proceedings of the Royal Irish Academy. 



Zimax arborum heads the above list in two senses, as it occurs from sea- 

 level to the summit of Croaghpatrick (2,510 feet), the highest altitude at 

 which I have collected in "West Mayo. Several species just fail to reach the 

 750-foot contour-line, so far as my experience has gone. Thus on Clare Island 

 V. pygmaea, V. antivertigo, and Z. excaratus live as high as 600 feet on the 

 shoulder of Croaghmore, above the Signal Tower, while A. laevis was taken on 

 Knocknaveen at about 500 feet altitude ; and on the mainland this slug was 

 noted on Croaghpatrick at about the same elevation. Zimnaea pereger was 

 collected in Lough Alisheen (650 feet altitude) among the Mweelrea mountains, 

 by F. Balfour Browne, this being the highest lake in which, up to the present, 

 it has been observed in the district. The remainder of the species occurring 

 in West Mayo are apparently confined to the low-lying parts of the county and 

 the sea-coast, few of them probably living above an altitude of 250 feet. 



10. RECENT OE HOLOCENE DEPOSITS. 



Sand-dune Deposits. 



Small deposits of shells occur in sand at Dooaghtry and on Clare Island 

 and Achill Island. None of these, however, appear to be of any great age, 

 and except on Inishbofin, where there is a fine section, nothing approaching 

 the great sand-hill deposits of Dog's Bay, 1 or the north of Ireland, 2 has been 

 found in the districts surveyed. 



In the section exposed along the shore of the Harbour on Clare Island 

 Mr. Welch has obtained Helicella itala, Vallonia pulchella,and Cochlicopa lubrica, 

 while in a section at Dooaghtry the same collector found H. itala, C. lubrica, 

 Zimnaea pereger, and Z. truncatula. The latter deposit had clearly been 

 formed at the bottom of a small lake or pool, which had, at some subsequent 

 date, been filled up with blown sand. It is quite possible that, owing to the 

 destruction of the greater part of the Dooaghtry dunes during the last hundred 

 years by westerly winds, many deposits have been destroyed. Nevertheless, 

 around the ancient graveyard, where a small area of the original dunes remains 

 and good sections are to be seen facing the river-course, I was unable to find 

 any shells except Helix aspersa and H. nemoralis. These occurred in the upper 

 layers, associated with the bones and teeth of various animals, and had evidently 

 been used for human food. From the deposits at Dugort, Achill Island, 



1 See R. D. Darbishiie on "Land Sheila at Dog's Bay, Connemara." Journal of Conch., iv, 

 317. 1885. 



2 R. J. Welch: Irish Nat., vii, 77-82. 1898. Ibid., xviii, 113. 1909. 



