&3 46 Proceedings of the Royal Irish Academy. 



are abundant in the environs of Westport, and as far west as Murrisk ; 

 while H. rufescens is found near houses as far north as Newport, and 

 sparingly by the roadside at Mulranny, where the roads to Ballycroy and 

 Achill part. South of Clew Bay all three species live near the harbour at Old 

 Head, upon the extreme edge of this district, the boundary of which I have 

 extended so as to include their habitats. Here S. putris occurs sparingly by 

 the side of the small stream which flows from the woods, and appears on the 

 verge of extinction. P. rupestris and IT. rufescens 1 are to be found among 

 limestone boulders near the old lime-kiln, associated with one of the rarest of 

 West Mayo land-shells, Vallonia costata. The limestone appears to have been 

 taken from the Boulder-clays forming the cliffs which face the bay some 

 distance to the east. The upper surface of this Boulder-clay probably marks 

 the post-Glacial level of the land, where Clew Bay now is. Thus it is possible 

 that the ancestors of these shells inhabited an area of land, which has since 

 been destroyed by the inroads of the sea. This idea is strengthened by the fact 

 that P. rupestris occurs on Dorinish, one of the many islands which stud the 

 bay, and the only one upon which land-shells have been collected. The semi- 

 marine species which I include in my list are three in number. Paludestrina 

 stagnalis is abundant round all parts of the bay (see Nathaniel Colgan's report 

 on the Marine Mollusca, Part XXII) ; P. ventrosa was brought to me by 

 F. Balfour Browne from the salt-marsh below Mulranny ; while Phytia myosotis 

 is no doubt common in many places, as it occurred south of Newport, in the only 

 habitat in which I searched for it. The following is a full list of species so far 

 found in the district. C signifies that the species was found near Castlebar, 

 W near Westport, N near Newport, M (Murrisk) between Westport and 

 Old Head, and B (Burrishoole) that it occurred between Newport and 

 Mulranny. Those species unmarked may be taken as generally distributed 

 in the district. 



List of Mollusks of the Clew Bay and Castlebar Areas. 



Limax maximus, W, B, C. A. laevis. 



L. arborum. [Milax sowerbyi, 2 W, B, M.] 



Agriolimax agrestis. M. gagates, W, B. 



1 H. rufescens probably owes its origin here to man's interference, and is surely an " escape " 

 from a former cottage-garden, situated close by. The other species are certainly native. 



- Since Milax sowerbyi, Avion hortensis and Hygromia rufescens are confined to the neighbourhood 

 of habitations, it is impossible to say whether they are "native" or only "naturalized." Their 

 standing is therefore given as * * * in the table at the end of this report. In the south-east of 

 England H. rufescens lives in uncultivated areas, but I have no record of its being found in Ireland 

 under such circumstances. Avion hortensis is certainly native in many parts of eastern and central 

 Ireland ; but in the west it appears to be just making its appearance. Many old records for this slug 

 should in all probability be referred to the dark-grey form of A. intermedins JN'ormand. 



