112 



Proceedincjs of the Roi/al Irish Academy. 



small fragile form (fig. 25) is often found 

 in peaty areas associated with Pisidium 



WD ED LD AN 

 FE TY AR DO 

 WMSL LE MO 



EM RO CV LH 

 WC NG LF WH ME 

 SC KG KD DU 

 CL NT QG GW Wl 

 NK LK ST KK WX 

 SK MG EC WA 

 WG 



casertamnn and F. personatum, where 

 other species of mollusca apparently 

 cannot live ; this form likewise occurs 

 on several of the western islands. Var. 

 eorva is frequent in many parts of the 

 country, but particularly in the central 

 and eastern districts, where it is some- 

 times the only form encountered. 

 The " Li7nneus glaber'" of Thompson, 

 Humphreys, and others is perhaps the 

 young of a slender form of this shell 

 which is sometimes found in marshes, 

 and to my own knowledge occurs in 

 the neighbourhood of Cork and Belfast, 

 two of the localities in which that species 

 was supposed to have been f oimd. This 

 species, like others of the genus, has a 

 well-marked lacustrine form. (Figs. 21, 

 22.) 



Limnaea truncatula (Miiller). 



Plate VII, figs. 29-32. 



Helix fossaria, Brown, Mem. Werner. 

 Soc, vol. ii, p. 530, 1818. Limneus 

 trimcatulus, Thompson, Cat. L. & F.W. 

 Moll, of Ireland, p. 32, 1840. 



Even more generally distributed than 



the last species, and, as it is the most 

 amphibious of the genus, it is often 



WD ED LD AN 

 FE TY AR DO 

 WMSL LE MO 



EM RO GV LH 

 WG NG LF WH ME 

 SG KG KD DU 

 GL NT QG CW Wl 

 NK LK ST KK WX 

 SK MG EG WA 

 WC 



found in places where it would be im- 

 possible for the other Limnaeae to exist. 

 It is frequent in wayside pools which 

 are quite di'ied up in summer ; but the 

 most remarkable habitat in which I 

 have met with it is the great sea-clifl 

 of Croaghmore, on Clare Island. On 

 the rock-faces of this cliff it lives up 

 to an altitude of close on 1000 feet, 

 associated with Sygromia fusoa. Pupa 

 cylindracea, P. anglica, Balea perversa, 

 and Clausilia hidentata, and must depend, 

 like the terrestrial species, for its supply 

 of moisture on rain and dew. There are 

 not even perennial runnels on this cliff. 

 In the Dingle peninsula it lives in similar 

 situations, and I have taken specimens 

 on Bi'andon Mountain as high as 

 1775 feet. The form met with in the 

 eastern counties and on the limestone 

 districts (fig. 30) is much larger and 

 more rugged than that which prevails 

 in many places in the west, which is 

 more delicate in texture and smaller 

 in size (fig. 29). Some localities in 

 the west yield specimens which, at a 

 cursoiy glance, might almost be mis- 

 taken for Snccinea ohlonga when dirty, 

 the shouldered appearance of the suture, 



