378 BATHYMETRICAL SURVEY OF 



One was the common D. gracilis, the other difficult to determine, owing 

 to the lack of fully matured examples, but almost certainly D. laticeps. 



Loch Ossian and Loch Ghuilbinn. The fauna of these lochs is in no 

 way peculiar. Desmids were scarce in Loch Ossian, and abundant in 

 Loch Ghuilbinn, where, among others, Staurastrum ophiura occurred. 



Loch Treig. Bosmina obtusirostris had a very long spine, approach- 

 ing the variety longispina, as found in Loch Morar. This is the only 

 large lake where we found the rotifer Triarthra longiseta. Skeletons 

 of Clathrulina were abundant. The phytoplankton was fairly rich in 

 species, and about a dozen Desmids were noted. 



An Dubh Lochan. This was examined very late in the season. 

 The chief peculiarity noted was the red colour of the Diaptomus, a 

 feature found in more marked degree in Lochan Lunn da-Bhra. 

 Desmids were abundant, and the two fine species, Staurastrum 

 braziliense and S. longispinum, occurred. 



Lochan Lunn da-Bhra. The Diaptomus in this loch was so deep 

 red that, when the nets were taken out after towing, they seemed to 

 contain blood. 



Loch nan Gabhar. From its shallow, weedy character, an abundant 

 fauna would be expected here, yet we found the collections exceptionally 

 poor. 



