THE MOLLUSCAN FAUNA OF THE OUTER HEBRIDES 285 



Pisidium personation. 



Lewis. In muddy ditch, Linshader, with P. casertanum, 

 numerous, 20th July 1918 (F. Montague Dyke). 



Pisidium pusillum. 



North Uist. Stream running out of Loch Fada, 24th May 

 1894, numerous (Thomas Scott); Balelone, July 1905 

 (J. Waterston). 



Barra. Sinclair Loch, 10th May 1894, numerous 

 (Thomas Scott). 



Pisidium obtusale. 



Barra. Very abundant in marshy ground at the foot of 

 Avon Mhor, June-July 1905 "referable to this species though 

 not strictly characteristic " (J. Waterston). 



It will thus be seen that the list of Hebridean land and 

 freshwater mollusca numbers 43 species, to which it ought to 

 be possible to add others by careful research. Analysing 

 the list, it will be seen that 26 are recorded for the Lewis, 

 1 for Harris, 15 for North Uist, 4 for Benbecula, 10 for 

 South Uist, 22 for Barra, 16 for the St Kilda group, and 1 

 for the Flannan Islands. 



That the details require working out in the various 

 island groups themselves is sufficiently manifest by the 

 fact that no less than 23 species are on record for one 

 group only, viz. : Agriolimax agrestis, Avion subfnscus, 

 A. ciraimscriptus, Zonitoides nitidus, Vallonia excentrica 

 Carychiutn minimum, Unio margaritifer, Pisidium casertanum 

 and P. personatum for the Lewis only; Punctum pygmeeum 

 and Vallonia pulcliella for North Uist only; Hyalinia lucida, 

 Hygromia granulata, Planorbis glaber, PI. crista, Pisidium 

 fontinale, and P. obtusale for Barra only ; and Hyalinia 

 nitidula, Hyalinia crystallina, Pupa anglica, Sphyradium 

 edentulum, Vertigo substriata, and Balea perversa for the St 

 Kilda group only. The slugs particularly have been very 

 imperfectly worked, as reference to the ubiquitous Agriolimax 

 agrestis will show. 



Published literature is very scanty, and it may be a 

 convenience to workers if I recapitulate such imperfect notes 

 as I happen to possess. 



84 2 L 



