23 22 Proceedings of the Royal Irish Academy. 



P. obtusale Pfeiffer. — "With the last species in Light-house Pool, and also 



occurred in Creggan Lough. 

 P. personatum Malm. — Widely distributed and common in the roadside pools, 



field-drains, and bog-pools. 

 P. milium Held. — Xot at all common, but was taken in Light-house Pool, in 



Lough Merrignagh, at Craigmore, and in the marsh north of Knocknaveen. 



Three species in the above list — ^1 ezxavatus, A. lamellata, and H.fusca, — 

 are almost confined to the Britannic area. These with Hygromia granulata, 

 a mollusk not found within the boundaries of the present survey, form a 

 small but interesting group of shells perhaps protected from exterminating 

 influences by the isolation of our islands. Judging by the geological 

 evidence, A. lamellata is retiring towards the north-west comer of Europe, as 

 I learn from A. S. Kennard that it is known from the Miocene of central 

 Europe, and it has been recorded from several Pleistocene deposits in the 

 south of England, 1 though not now known to live in these districts. 



The distribution of the Pisidia is uncertain, owing to the difficulty of 

 recognizing our species in Continental lists. The remaining species are 

 widely distributed in western Europe, but five are mainly coastal in their 

 range, and are unknown from central or northern Europe. Sixteen are almost 

 eircumpolar in their distribution, or there exist closely allied species in the 

 polar lands of Asia or America. Thirteen are recorded by Kennard and 

 Woodward (ibid.) from the Pliocene of the south of England, and thirty-eight 

 from the Pleistocene. The remaining seventeen species, absent from the 

 Pleistocene, have a mainly western distribution, and perhaps did not live in 

 Pleistocene times in the localities where deposits of that age are known ; or 

 they are slugs : or they have fragile shells not likely to become fossilized. 



The Mullet. 



So isolated a district is the peninsula of The Mullet, that it might almost 

 be compared with the neighbouring islands, rather than with the adjoining 

 parts of the mainland. Perhaps one might be forgiven for terming it an 

 " island " still connected to the mainland by a " land-bridge." It will be at 

 once seen, therefore, that its fauna deserves special attention. Unfortunately 

 one evening and one long day were all the time that I was able to devote to 

 its exploration, during which time a cold, dry, northerly wind blew con- 

 tinuously. Thus my list must be correspondingly short, and the absence from 

 it of many species, such as Limax arborum, Pyramidula rotundata, and 



1 See Kennard and Woodward : On the Post-Pliocene Xon-Marine Mollusca of the South of 

 England, Proceedings of the Geologists' Association, xvii, (5;, 213—260. 



