114 



Proceedings of the Royal Irish Academy. 



rare in tlie south-west, west, and north, 

 and absent from many districts, some of 

 considerable area. In the -western and 

 north-western counties it is sometimes 

 replaced hy Planorlis glaler. It has 

 been stated often that these two shells 

 do not live together, but this is certainly 

 not true in Ireland. 



Planorbis glaber Jeffreys. 



= P. laevis Alder. 



Planorbis laevis, Thompson, Cat. L. and 

 F. W. MoU. of Ireland, p. 34, 1840. 



WD ED LD AN 



FE TY AE DO 



WMSL LE MO 



EM RO CV LH 

 WG NG LF WH ME 



SC ^c KD DU 



CL MT QC cw wi 

 NK LK ST KK ^^'X 

 SK MC EC WA 



WC 



Somewhat similar to Linmaea atiricu- 

 laria in its distribution, and, although 

 widely scattered in all four provinces, 

 it is exceptionally local in all but the 

 western and north-western counties ; 

 and even in these, it is confined to the 

 maritime lakes. It also occurs on 

 several of the lakes on Achill Island, 

 but otherwise has only been taken on 

 the mainland. Specimens from "West 

 Donegal are narrower in the whorls 

 than typical English examples, and 

 appear to almost grade into the Plan- 

 orlis areticm of Westerlund. These 

 Donegal examples closely resemble the 

 form found in Lough Skaill in the 

 Orkneys. 



Planorbis crista (Linne). 



Tiirho Nautileus, Brown, Mem. "Werner. 

 Soc, vol. ii, p. 522, 1818. Planorlis 

 imbricatus, Thompson, Cat. L. & F."W. 

 Moll, of Ireland, p. 35, 1840. 



WD ED LD AN 

 FE TY AR DO 

 WMSL LE MO 



EM RO CV LH 



WG NG LF WH ME 



SG £C KD DU 



CL NT QC cw WI 



NK LK ST KK WX 



SK MC EC WA 



WC 



Generally distributed throughout the 

 country, but perhaps more abundant 

 in the west, and found on many of 

 the western islands. In some of the 

 central counties, this sheU appears 

 rare, and has not so far been recorded 

 for Carlow and "King's Co. The three 

 forms — spinulosa, cristata, and nautileus^ 

 — occur in about equal numbers. 



Planorbis carinatus Miiller. 



Plate VII, figs. 53-55. 



Melix planata, Brown, Mem. "Werner. 

 Soc, vol. ii, p. 524, 1818. 



Generally distributed over the central 

 and eastern counties, becoming rare to- 

 wards and fijnally absent from the south- 

 west, west, and north-west. Specimens 

 from the central districts are generally 



' Clessin, Deutsche Exoursions-MoUusken- 

 Faiina, p. 429. 



