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Part III. — Thirteenth Annual Report 



reach of Castlebay. In order to overcome the natural obstacles in the 

 way of obtaining a supply of water for the use of the village, the follow- 

 ing ingenious device has been adopted : — a series of metal pipes carefully 

 fitted together have been laid from the loch up over the high ground and 

 for some distance down the valley on the other side, thus forming a 

 very effective siphon. The water, on leaving the outlet end of the siphon, 

 runs down the natural water-way of the valley to the store-pond from 

 which the village of Castlebay is supplied. Loch Cadha M6r is in this 

 way made to contribute its share of the water required by the people of 

 the village. 



One of the most common of the organisms observed in this loch was 

 Diaptomus serricomis. It is somewhat singular that this hitherto 

 apparently rare British Copepod was the only Diaptomus observed in 

 the Barra lochs, and it occurred in no fewer than eight of them. It was 

 also the only species of Diaptomus observed in the North Uist lochs, 

 and in several of the lochs of Shetland that were examined last year (see 

 separate report on the Shetland Lochs by myself and Mr Duthie F.O.). 

 Eight species of Copepoda, six of Ostracoda, and eleven of Cladocera, 

 were obtained in Loch Cadha M6r ; Gammarus was also fairly common ; 

 a few Limncea peregra and Pisidium pusillum were the only Mollusca 

 observed. The altitude of Loch Cadha Mor is over 500 feet above sea- 

 level. 



Ben Heaval, which is the highest hill on the Island of Barra, has an 

 altitude of 1200 feet above the sea. At the time of my visit there were 

 several pools that had been formed by the rain water collecting in the 

 hollows scooped out of the peat, which, in some places near the summit 

 of the hill, forms beds of considerable thickness. A comparatively large 

 number of Crustacea were obtained in these pools, among which were 

 Diaptomus serricomis, four species of Cyclops, three of Harpacticidw 

 two of Ostracoda, and seven of Cladocera. Fine specimens of Acanthole- 

 beris curvirostris were obtained in the Ben Heaval pools. Alona rustica, 

 n. sp. — an apparently new Cladoceran — was obtained in the gatherings 

 from Loch Cadha Mor (see Notes on rare Crustacea at the end of the 

 paper). 



Loch an Ail. 



Loch an Ail is a small loch on the east side of, and a short distance 

 from, the highway between Ruliess and Balnabodach, and occupies a 

 uatural hollow in the rocky ground forming one side of the narrow water- 

 way through which the sea flows into Loch Obe. Its altitude is about 

 40 feet above sea-level. Some large specimens of (?) Bosmina longirostris 

 were obtained here (see note on Bosmina, with drawings of specimen). The 

 species observed and identified in the tow-net gatherings from Loch an 

 Ail comprise Planorbis nauiileus, Gammarus duabeni, together with nine 

 species of Copepoda, four of Ostracoda, and four of Cladocera. 



Loch Scotagary. 



The south-east end of this loch almost touches the highway a short 

 distance north of the village of Ruliess. It is one of several small 

 lochs situated in a stretch of bog-land that extends for a considerable 

 distance to the north and west of the village just referred to. . Loch 

 Scotagary is about 100 feet above the level of the sea, and moderately 

 deep. 



The Crustacea obtained in this loch comprised seven species of Copepoda 

 (including Diaptomus serricomis), and nine species of Cladocera ; Gam- 

 marus duabeni was frequent. 



