192 
BATYHMETRICAL SURVEY OF 
found in the district, they were never all found together in one loch, 
as was commonly the case elsewhere in Sutherland. The Baphnia in 
most of the lochs was the typical D. lacustris. In one loch this was 
associated with D. galeata^ while in three lochs D. galeata was alone 
observed. Leptodora was only observed in Loch Skinaskink, and 
Bythotrephes was not observed at all. 
While the fauna thus offers little that is remarkable, the flora, on 
the other hand, is notable for the great wealth of Algse, especially of 
Desmids. Over fifty species of Desmids were observed, and between 
thirty and forty of these sometimes occurred in one loch. Messrs. 
West, commenting on the Desmid flora of this part of Scotland, state 
that the plankton is unique in the abundance of its Desmids, and that 
the most conspicuous of these are of a distinctly western type, being 
found in Europe only along the extreme north-western coasts, while 
in North America they are eastern species. The southern and eastern 
limits of this remarkably rich area in Scotland cannot yet be fixed ; 
in Sutherland it extends right across Scotland. An examination of 
many hill lochs in Perthshire and in the south of Scotland showed no 
such rich flora there. When the distribution of the Desmid flora is 
worked out, it will be of interest to observe whether the area covered 
by those western species coincides with that occupied by the northern 
Calanidse, Diaptomus Wierzejskii and D. Jaciniatus, which are so 
generally distributed in Sutherland, though they also occur in many 
spots further south. 
Loch Assynt . — ^The plankton of this loch closely resembles that of 
the larger lochs in the south, only the typically pelagic Entomostraca 
and Rotifera being present. It is noticeable that neither Diaptomus 
Wierzejskii, D. laciniatus, nor Daphnia galeata, species widely dis- 
tributed in the district and also occurring in many of the large lochs 
further south, was observed here. The loch further resembles many 
other large lochs in the presence of numerous skeletons of Clathrulina 
elegans. The only Rotifer calling for mention is Triarihra longiseta, 
a species not usual in large lakes. Unlike the other lochs of the 
district, there were very few Desmids in the plankton. The quantity 
of plankton was very small. 
Loch Lurgain. — The fauna comprised only the usual pelagic species, 
among which Cyclops strenuus was most abundant. The Daphnia was 
D. galeata. Diaphanosoma hrachyurum was present in some numbers. 
The flora was remarkable for the number of Desmids, especially of the 
genus Staiirastrum, including the beautiful large species, S. longis- 
pinum and 8 . arctiscon. 
LjocIi Bad a’ Ghaill . — ^The somewhat meagre plankton was almost 
exactly of the type found in deep lochs, differing only in the greater 
abundance of Rotifera, among which were Plcesoma, Gastropus, and 
Triarihra. The commonest animal was Cyclops strenuus. About a 
