igis. Phillips & Stelfox. — Range of Pisidium hibernictim. 35 



the second from Iver, Bucks. It was next recognized from 

 some of the various tarns in the Snowdonian range, in 

 North Wales, amongst shells collected by Mr. Charles 

 Oldham ; and it was found to be well represented in Mr. 

 H. Overton's gatherings from the Sutton Coldfield district 

 in Warwickshire. Numerous other English and Welsh 

 records have since come to hand, as well as one from the 

 Isle of Man and one from Norway. 



Owing to the fact that the original habitat was a moun- 

 tain tarn, P. hibernicitni has become associated in most 

 conchologists' minds with an alpine fauna ; but as a matter 

 of fact it has occurred to us in almost all conceivable habitats 

 as the following lists show. It is worthy of notice, however, 

 that it has not been observed to inhabit the type of habitat 

 — often dry for long periods — so associated in one's mind 

 with P. personatiim, and that in rivers of large size it w^ould 

 appear to be rare. It occurs at all altitudes from sea-level 

 to the highest tarns in Ireland and Wales ; in the " peatiest " 

 of lakes and in those whose waters are most saturated with 

 lime ; but it would appear to reach its finest condition under 

 the latter environment, the shell from Crow's Lough, Gorty- 

 madden. South Galway, being the most perfect development 

 of the species we have yet seen (Plate I., figs. 7 and 8). Some 

 of Dr. Scharff' s original examples are the largest that have 

 been taken anywhere, and no subsequent visitor to L. 

 Nagarriva has obtained, from there, specimens of equal 

 size. As pointed out by Mr. Woodward (Cat., p. 118), the 

 specimens from, the type locality " represent an abnormally 

 swollen form " and, we would add, are rather depauperate, 

 except in size, owing no doubt to the very peaty nature of 

 their habitat. The more normal and usual lowland form is 

 more elliptical, with smaller and more prominent umbones 

 and is less tumid. Most of the English and Welsh examples 

 are of the last form. Mr. Woodward {loc. cit.) says " Wester- 

 lund's measurements are: — Long. 3.5, Alt. 3.5, Crass. 

 3.5 mm., but a larger specimen in the National Museum, 

 Ireland, is Long. 4.5, Alt. 4 mm. The West Galway [L. 

 Gowlanagower] specimens were smaller and less globose : 

 2.8x2.5x1.8 mm. ' ' The maj ority of our specimens come 

 nearer the latter measurements, 



A 2 



