BIOLOGY OF THE SCOTTISH LOCHS 
299 
lochs where it occurred is tidal (Loch Wester) ; the others are little 
above sea-level. 
Latona setifera (MiilL). — There are only 12 records of this beauti- 
ful animal — 1 loch in Ross (Loch Ussie) ; 4 in Inverness (Lochs Ness, 
Oich, Laggan,and na h-Earba); 6 in Perth (Lochs Kennard, Sron Smeur, 
Tilt, na Bi, Rannoch, and Laidon) ; and 1 in Kirkcudbright (Loch 
Trool). Dr Scott's records show a wider range, giving extra localities 
in Perth and Inverness, and many records for the Shetland Islands. 
Bosmina longirostris^ Mlill., and B. ohtusirostris^ Sars. — The Arctic 
species, B. ohtusirostris^ is all but universal in Scotland, being absent 
only from some small lowland districts, chiefly in the south-east. 
B. longirostris occupies these lowland districts, usually in the variety 
cornuta. There is reason to believe that B. longirostris often exists 
along with B. ohtvsirostris in the Highland region, the former as a 
littoral, the latter as a plankton form. 
B. coregoni, Baird, is only known from two lochs — Loch Heilen 
in the extreme north (Caithness), and Castle Loch in the extreme south 
(Dumfries). 
Ophryoxus gracilis^ Sars. — Only recently detected in Britain by 
Mr Scourfield, and only known in two of the lochs of the Caledonian 
Canal (Lochs Ness and Lochy), and in the Canal between these lochs. 
In Europe it is purely a northern species, only found in countries 
bordering on the Arctic Ocean. In the United States it is found 
farther south, in Minnesota and Wisconsin. 
Ihjocryptus acutifrons^ Sars. — Known in two far-separated districts 
in Britain, Sutherland and Norfolk. 
Ca7idona elongata^ Brady and Norman. — The only known stations 
for this species, Lough Neagh in Ireland, and Loch Dun na Seilcheig, 
near Inverness, Scotland, offer a puzzle in distribution, but it cannot 
be said that the intervening region has been sufficiently well searched 
to demonstrate their real isolation. 
Rotifera. — ConocMlus volvox\ Ehr., and C. unicornis^ Rouss. — 
Both are generally distributed and are sometimes found together, 
though rarely. The dominant species in Scotland is C. unicoiiiis. 
Microdina pcwadoora^ Murray. — Common among the marginal 
vegetation of pure lochs in Scotland, and also in streams ; it is as yet 
unknown elsewhere except in the Lake of Geneva, and in New Zealand. 
Philodina hamata, Murray, P. laticeps, Murray, and P. laticoiiiis, 
Murray. — Though only as yet recorded from Scotland, these species 
are likely to be as widely diffused as the Gammarus with which they 
are found. P. hamata is only known in two lochs, far apart (Loch 
Tay and St Mary's Loch), and P. laticornis in two lochs of the 
Caledonian Canal (Lochs Ness and Lochy). P. lat'iceps is commoner. 
Callidina angusticoUis^ Murray. — One of the most thoroughly 
