June, 1914. 
Ihe Irish Naturalist. 
125 
LAND AND FRESHWATER MOLLUSCA OF THE 
VALLEY OF THE ROE, BENEVENAGH AND 
MAGILLIGAN, CO. DERRY. 
BY A. W. STELFOX. 
Although eighty-eight species of land and freshwater 
shells have been reported to occur in the County of London- 
derry/ no locality lists, such as those existing for the adjoining 
counties of Antrim and Donegal, have been published. 
Therefore I take this opportunity of recording the species 
collected during a week's stay in the Roe Valley, at Easter 
1913, when in the company of Messrs. R. J. Welch, Nevin 
H. Foster, S. Wear, and a few other members of the Belfast 
Naturalists' Field Club. At the same time I include the 
work done by Messrs. J. N. Milne, R. J. Welch, and myself 
at Benevenagh and on the Magilligan flat from Downhill 
to Walworth Wood, on various occasions in years past. 
This district is extremely varied in its geological features. 
On the east it is overshadowed by the north-western escarp- 
ment of the great basaltic plateau of Antrim and Derry, 
of Eocene age, which covers deposits of Chalk and Triassic 
sandstone. Near Dungiven the Roe cuts in places through 
sandstone of Carboniferous age, while between the Roe and 
Lough Foyle on the west, the pre-Cambrian schists form 
low hills, outliers of the Sperrin Mountains to the south. 
These schistose rocks are frequently intersected by great 
belts of crystalline limestone of the same geological age. 
The greater portion of the ground is covered by Glacial 
drift, composed mainly of schistose rock -fragments and of 
Carboniferous and Triassic sandstones ground into a pasty 
mud, which does not much attract a variety of mollusks. 
Where, however, the limestone outcrops occur, and especially 
in the glens of Banagher and in Benady Glen, south of 
Dungiven, splendid natural ground is to be found, which 
shelters a luxuriant molluscan fauna. In the locahties just 
mentioned the majority of the species are shade-loving ; 
^Stelfox : A List of the L. and FAV. Mollusks of Ireland. Proceedings 
R. I. Acad., vol. xxix., Sect. B. No. 3. . •■ 
