MILNE : CONTRIBUTIONS TOWARDS IRISH MOLLUSCA. 413 



the north-east corner of the island. Resulting from this, the 

 localities cited will be few: — the fields and gardens at Dugort, 

 the Colony, Slievemore, and the Signal Tower- the sandhills on 

 the Warren, and at Ship Point, and on Keel Common; and the 

 beaches of Dugort and Annagh Bay. 



But there are, besides, indications to be found of the 

 nature of the fauna before the reign of peat, when the island 

 was covered with forest, in a small portion of old surface 

 uncovered in the banks of a stream, near Lough Nambrack; 

 and a few land shells mixed with the debris of bones, limpets, 

 whelks, periwinkles, and charcoal, on the shellmounds of Keel. 

 From these sources I will endeavour to get some light on 

 the reasons of the rather peculiar distribution of Achill mollusca. 

 The freshwater species are neither numerous nor particu- 

 larly important, and may be disposed of first. 

 Pisidium pusillum. — The only bivalve found was P. 

 pusilhim, v/hich, however, was very plentiful in its locali- 

 ties. It occurs on the mainland in peat dykes, near 

 Newport; and in Achill I found it in wet moss on the 

 shore at Annagh Bay, where the overflow of Lough Nakee- 

 roge dripped down to the sea; and in immense numbers 

 in a ditch of a field by the Colony, as dry a spot as it 

 could have chosen in that very damp locality; besides 

 these localities on land, there were a few in a brook 

 below Dugort. 



None of the Pectinibranchiate snails seem to inhabit 

 the island ; though Bythinia te?itaculata and Valvata pis- 

 cinalis swarm in every ditch and brook from Westport to 

 Newport ; they stop with the limestone. 

 Among the Planorbes, 

 P. albus and P. contortus are just as numerous within just 

 the same limits; P. naiitileus gets nearer Achill, as far as 

 Bunnamucka Lough at Molrhany, but on the island their 

 places are filled by P. glaber, which occurs in two lakes 

 on the warren — Lough Nambrack and Lough Doo. As 



