Clare Island Survey — Land and Fresh-water Mollusca. 23 3 



species, which in many districts underlie our peat-bogs, have been scientifically 

 examined, we shall be in a better position to discuss the probable time of the 

 arrival in Ireland of species of the eastern group. 1 11 several cases where the 

 pre-peat marls have been examined, the species contained in them present a 

 more western facies than that of the fauna now living in the district. One 

 of the characteristic species of these marls, in certain districts, is Planorbis 

 glaber, which at the present-day has a distinctly anti-central or "western" 

 range in Ireland. Species with such a range are often referred to as " calci- 

 fuge," but, in the case of the Mollusca, I think this term is hardly applicable. 

 The western species do not appear to object to the presence of lime, yet evi- 

 dently they have been unable to maintain their position upon the limestone 

 areas, probably owing to increased competition in these favourable districts. 



The nomenclature which is employed throughout this report is that given 

 in the " List of the Land and Fresh-water Mollusks of Ireland " (Proc. of 

 E.I. Acad., xxix, Section B, No. 3. 1911). All the records given for thePisidia 

 are founded upon specimens verified by Mr. B. B. Woodward, to whom I 

 tender my most sincere thanks for his invaluable kindness in identifying 

 specimens sent to him. 



The area dealt with, as will be seen by the accompanying map (fig. 1), 

 is probably more extensive than that covered by most workers on the Survey. 

 It includes, besides Clare Island and the adjacent mainland from Belmullet 

 to Killary, Achill Island, the Bills of Achill, Inishturk, Inishbofin, and Caher 

 Island, and extends as far inland as Castlebar. The greater part of this area 

 belongs to West Mayo according to Praeger's division of Ireland. 1 Inishbofin, 

 however, is in West Galway. 



2. FIELD-WORK 



Until the commencement of the Clare Island Survey only one paper 

 dealing solely with the Mollusca of West Mayo had been published. I refer 

 to that by J. G. Milne (4), which deals mainly with the Mollusca found by 

 him on Achill Island in 1891. Some collecting by Miss A. L. Massy, 

 P. H. Grierson, G. P. Farran, and R. J. Welch had, however, brought the list 

 of species for this division at the commencement of this Survey up to fifty- 

 three. When the " Irish List" (18) was published in 1910, this number had 

 increased to eighty-eight ; since then no further additions have been made. 



During the preparation of the present report I have spent fifty days in 

 the district, viz., 8th till 16th April, and 4th till 16th September, in 1909 ; 



1 Irish Topographical Botany. 1901. 



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