114 
THE FISHES OP LOCH LOMOND AND ITS 
TRIBUTARIES. 
By Alfred Brown. 
IN submitting a Catalogue of the Fauna of any particular area^ 
it is perhaps desirable to give a sketch, however slight and 
imperfect, of the physical conditions and general surroundings of 
the district under review. 
The area with which we are at present concerned is that of 
Loch Lomond, and the tributary streams which complete its 
system ; — a district which, towards its northern boundary, pre- 
sents a landscape barren, steep, and rugged in the highest degree, 
while in the south it suddenly broadens out into the fertile valleys 
and rich fields of the Lennox country. The sharp boundaries be- 
tween these extremes, as seen at Balmaha and Rossdhu, appear 
to constitute the very gates of the Highlands. 
Loch Lomond, then, is a sheet of water some 24 miles long 
by about 6 miles broad at its greatest width ; narrow and deep at 
its upper or northern end, and rapidly widening and shoaling at 
about 9 miles from its lower extremity, where the River Leven, in 
a deep and rapid stream, carries its surplus waters to the Clyde, 
which it enters at Dumbarton. 
The surface of the loch is but little raised above the sea level, 
and a subsidence of a few feet would convert it into an arm of the 
Clyde Estuary, a condition which, without doubt, existed at a very 
recent geological period, as we find — in the cuttings formed 
when making drains, and in the clay banks exposed and cut into 
by the action of the water — numerous shells of marine bivalves, of 
species still living in the adjacent seas, such as Mytilus 77iodiolus, 
Pecten maximus, Cyprina islandica, and species of Tellina, all of 
which are characteristic of our post-tertiary deposits. 
So far as I know, no extinct species have be^n collected from 
these clay banks or cuttings ; but one shell, Feden islandicus^^ is 
there found which has since retired from British waters, and is 
now only recorded from more arctic regions — Norway, Iceland, 
Labrador. 
I imagine that during the period of elevation which culminated 
1 Dr. J. Gwyn Jeffreys obtained this species at depths varying from 80 to 
170 fathoms among the Shetland Islands. See Report on Dredging among 
the Shetland Isles, Brit. Ass. Report, i867.~ED. 
