58 



THE LAND AND FRESHWATER MOLLUSCA OF lONA. 



By JOHN F. M US HAM, F.E.S. 



(Read before the Society, Octo1)er 13th, 1912). 



In addition to my own experiences, I have been enabled, through 

 the kindness of Mr. J. R. le B. Tomlin, who drew my attention to 

 the same, to make extracts from an earlier paper read by Mr. 

 A. Somerville, B.Sc, F.L.S., before the Natural History Society of 

 Glasgow on April 24th 1888, on the Land and Freshwater Mollusca 

 of this island. 



Mr. Somerville writes thus: — -"On the occasion of a visit to the 

 island of lona in October, 1887, I devoted a short time to the 

 investigation of its Land and Freshwater Mollusca, and though I 

 cannot claim to have exhausted the species occurring on the island, 

 it may be of interest to mention that sixteen rewarded search, one 

 being aquatic, and the remainder, including the slugs, terrestrial." 



Thus, after a lapse of 25 years, our experiences almost tally, each 

 taking 16 species, though not quite identical. 



He further writes: "The western and uninhabited side of lona 

 faces the Atlantic, and is rocky excepting towards the middle, where 

 there is an open bay from which stretch up sandy, grass-covered 

 undulations. Here Helix ericetorum ]\Iiill. and Bulhnus aaitus (Miill.) 

 were swarming, as they do in many similar places on the west of 

 Scotland from the Butt of Lewis to the Mull of Cantyre, and on 

 the sandy Ayrshire coast. 



On the eastern or inhabited side of the island, under stones near 

 human dwellings, most of the species were found,, and of these 

 the most plentiful was Helix sericea Miill., a local, though widely 

 distributed form, so named from its epidermic covering of fine white 

 silky hairs, which do not easily rub off." 



Nowadays, however, one's attention cannot fail to be drawn, as 

 soon as the village street is left behind, to the quantities of Zr^'//.:v 

 aspersa, Helicella itaht, and H a ait a, which abound everywhere ; 

 further added to on the eastern side, by quantities of dead and 

 bleached Helix 7iemoralis L., H. horteiisis (Miill.), and a few H. 

 arbustoritm (L.). 



This bleached condition of practically all the living shells noticed 

 during my visit is not alluded to by Mr. Somerville. 



I found that living full-grown specimens of Helicella itala and H. 

 acuta were scarce, though juveniles swarmed wherever it was sandy; 

 incidentally I might allude to the partiality for old leather, beloved 



