ee Oe Oe ee em 
of the Fishery Board for Scotland. 285 
water, calculated from the bench mark on Kenmore Bridge, is found to be 
346 feet above the sea. The general outline of the loch somewhat 
resembles the letter S in form but with the ends only slightly curved. 
The lower portion of the letter is represented by the part from Killin to 
Ardionaig and extends E. 25° N. about 54 miles, the middle portion is 
represented by the part from Ardionaig to Fernan and extends N. 30° E. 
about 52 miles, and the upper portion is represented by the part extending 
from Fernan to Kenmore, and which lies in the same direction as the 
west end, viz..—E. 25° N. The length of this portio is about 34 miles. 
-The deepest part of the loch is opposite Skiag, or a lituie over 5 miles ina 
‘bee line’ from Kenmore; the depth here is 85 fathoms or 520 feet. 
From this deep part of the loch the bottom rises gradually but more or 
less irregularly towards each end. When the loch is standing at its 
summer level the western margin is often covered with thin patches of 
bright red sand which, on examination, is found to be composed almost 
entirely of minute fragments of garnets; numerous fragments of 
garnetiferous schist may also be obtained scattered about the shore at the 
east end of the loch. 
INVERTEBRATE Fauna OF Locu Tay. 
The Loch was examined by means of a tow-net worked from a rowing 
boat kindly placed at my disposal by a friend in Kenmore. No examina- 
tion was made of the bottom of the Loch except where the water was 
shallow, that is between the steam-boat pier and the ‘ Minister’s Island’ 
on the south side, and from Aidan’s Isle eastward on the. north side. 
Pelagic crustacea were scarce in all the surface and under-surface gather- 
ings, but they included one or two forms of interest, such as the curious 
Bythotrephes and the beautiful Leptodora. On the other hand, the 
material collected by dragging the tow-net through and among the bottom 
vegetation found growing in some of the shallower parts and especially 
in the vicinity of the ‘Minister’s Island’ proved to be rich in micro- 
organisms ; over twenty species of crustacea were obtained in this way. 
Several species of Mollusca, Coleoptera, Arachnida, the larvee of dragon- 
flies and other insects, Rhizopoda, Rotifera, &c. were also observed in 
the same material. In the following lists I propose to give a record only 
of the species of Mollusca and Crustacea obtained, 
THE MOLLUSCA. 
Comparatively few species of Mollusca were observed in Loch Tay, 
and this paucity of molluscan species corresponds with what I have 
observed in the investigation of other-deep fresh-water Lochs; the 
conditions physical or otherwise of such lochs do not seem to favour the 
development of the Mollusca. 
1. LAMELLIBRANCHIATA, 
Pisidium pusillum (Gmelin). Frequent, 
rt fontinale (Drap). Scarce. 
2, GASTEROPODA. 
‘r t but generally of 
Valvata piscinalis (Miller). i \ ee ath y 
U 
