23 6 Proceedings of the Hoijul Irish Academy. 



cultivated ground or sand-dunes along the coasts. Fresh-water lakes and 

 pools are numerous, but small and often peaty, except where these lie among 

 the sand-hills, the latter being usually highly calcareous. In Achill Island. 

 The Mullet, and near Louisburgh the coastal lakes form one of the chief 

 topographical features. The Clew Bay and Castlebar division is low-lying 

 and undulating, composed mainly of Carboniferous and metamorphic 

 rocks, which are generally covered with calcareous Glacial drift, in which lakes 

 and waterways are naturally numerous. 



As might be expected, the last-mentioned district contains the bulk of the 

 fresh-water mollusca included in the total list, for, although many of these 

 shells are also met with in the Louisburgh district, the fresh-water snails are 

 but poorly represented in the remaining areas. In the case of the slugs and 

 terrestrial shells the contrast between Clew Bay and Castlebar and the other 

 districts is not so strongly evident on paper. Yet the limestone area shelters 

 at least one species, Pyramidula rupestris, which is absent from the other 

 districts. On the other hand, Zonitoides excavatus appears to be absent from 

 the limestone area, but perhaps occurs in some unworked corner of it, where 

 the metamorphic rocks are exposed or where non-calcareous Boulder -clay over- 

 lies the Carboniferous rocks. Along the southern shores of Clew Bay, between 

 Belclare and Murrisk, the maximum contrast is to be observed between the 

 " calcicole " ' and " calcif uge " ' fauna. At this point, known as the Deer- 

 park, the mountain slopes almost to the sea-shore and is covered in places with 

 a dense tangle of native scrub, with intervening stretches of heath-land, while 

 between the base of the mountain and the sea there extends a narrow flat belt 

 of calcareous Boulder-clay lying upon the Carboniferous limestone. The 

 road from Westport to Louisburgh runs along the base of the hilly 

 ground, and the wall along its southern side forms the actual boundary 

 between the limestone and non-calcareous areas. Upon this wall we find such 

 a characteristic calcicole plant as Ceterach officinarum, and the mollusk 

 Pyramidula rupestris, while five yards up the hillside the prevailing flora is a 

 calcifuge one, consisting largely of Calluna vulgaris and Erica, cinerea, with 

 patches of Hazel, Holly, and Birch wood. Among this scrub, Z. excavatus is 

 common, associated with shade-loving, but not necessarily calcifuge species, 

 such as Hygromia fusca, Acanthinula latnellata, and Acicula lineata. 



Upon the mainland twenty species have been found which are as yet 

 unknown from any of the adjoining islands. These are mainly fresh-water 

 species, and ones which have a central and eastern range in Ireland and a 

 southern distribution in Great Britain. In the following lists those records 

 which are founded on doubtfully native specimens are not considered. 



I use these terms for want of better. 



