432 BATHYMETRICAL SURVEY OF 



Mr. Scourfield as D. laticeps) is somewhat small and pale in colour. 

 In other districts, and especially in hill lochs, it is of larger size and 

 brighter colours blue or occasionally red. There is some doubt as to 

 the identity in all cases, and naturalists have given different identifica- 

 tions of the Loch Ness animal. 



D. laciniatus, in contrast to D. laticeps, was only found to the west 

 of the Glen, in lochs high above the sea. To the east, though it was not 

 in any of the lochs surveyed, it was in some lochans at a great elevation 

 on Carnahoulin. 



Desmids. The conspicuous plankton desmids, which constitute 

 probably the most distinctive feature of the western Scottish plankton 

 are not very well represented in the lochs of the Ness basin. There are 

 few species, but they include several of the largest and most beautiful. 

 They show no marked preference for the one side of the Glen more than 

 the other, but the greatest number of species is in Loch Aslaich, which 

 lies west of Loch Ness. 



Micrasterias apiculata, var. fimbriata, was in Loch Aslaich, and the 

 var. bracliyptera was found only once in Loch Ness. 



M. radiata, Hass (M. furcata). This very local species was in Loch 

 Aslaich. 



Staurastrum furciyerum, Breb. In Loch Bran, at Foyers. 



S. longispinum (Bail.). In Loch Aslaich and several neighbouring 

 lochs. 



S. ophiura, Lund. Loch Ness and Loch Aslaich. 



S. sexangulare (Bulu.). Loch Garth, near Foyers. 



S. brasiliense, Nordst. Loch Aslaich. 



Euastrum verrucosum, Ehr., Micrasterias papillifera, Breb., 

 Xanthidium antilopeum (Breb.), Staurastrum gracile, Rolfs, Stauras- 

 trum lunatum, var. planctonicum, West, and one of the beaked Closteria, 

 which I identify as C. setaceum, Ehr., are the most generally distributed 

 desmids in the basin. 



Crustacea. Apart from the Calanidse, a few of the Crustacea appear 

 to be local in the district. 



Sida crystallina. Only seen in Loch Ness and Loch Aslaich. 



Diaphanosoma bracliyurum . Only noted in the lochs of the Great 

 Glen and some lochs to the west. The eastern lochs were doubtless 

 surveyed before its season. 



Holopedium gibberum. Noted in scarcely half the lochs, but those 

 on both sides of the Glen and at all elevations. 



Leptodora was only seen in the lochs of the Glen and Loch Tarff ; 

 Polyphemus in the Glen and some lochs to the west; Bythotrephes in 

 the Glen and Lochs Tarff and Ruthven to the east. 



Rotifera. Conochilus unicornis was generally distributed; C. volvox 

 only in Lochs Ness, Laide, and Knockie. 



Floscularia pelagica. Lochs Ness, Oich/and Uanagan. 



