6 o TRANSACTIONS — PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
4.—ZOOLOGY. 
A.— The Mollusca. 
By H. Coates, F.R.S.E. 
The River Tay,'being a swift-flowing stream throughout the whole 
of its course, is not very rich in fresh-w’ater Mollusca. Some of the 
commoner species, however, are fairly abundant amongst the shingle 
of the shallower parts, and particularly in the stretch of river below 
Perth, from Kinfauns to Invergowrie, where the current becomes less 
strong. The various deadwaters in the upper portion of the valley, 
from Logierait to Stanley, are fairly productive, and would probably 
prove to be even more so if systematically examined. In addition to 
the river itself, and its former channels, certain ponds, ditches, and 
streams which occur on the haughlands have yielded a good many 
species. Amongst these may be mentioned the ponds at the top of 
the North Inch, near Perth, and the Mill Lade which flows past 
Tulloch. The Old Harbour below Perth has also yielded some 
interesting forms. 
As regards Land Mollusca, the banks of the river will w'ell repay 
careful examination. Especially is this the case at places where the 
soil is kept dam.p by overhanging vegetation, and where there are 
rocks or loose stones. In such localities some species, such as zonites 
cellarius^ are remarkable for the large size which they attain. The 
following list could have been considerably increased if the higher 
ground in the immediate neighbourhood of the river had been in¬ 
cluded, but the area has been limited to that prescribed, namely, the 
banks and the lower haughlands. 
In all cases representatives of the species named will be found in 
the Perthshire Natural History Museum, where they may be examined 
by those who wish to confirm the records for themselves. 
SphcEriiim coriteum^ L.—Common in standing or slow running 
water. 
Unio margaritifer^ L. (the Pearl Mussel).—This is by far the most 
important of the Mollusca of the Tay, both on account of its size and 
its commercial value. It is found throughout the entire course of the 
river, and at all depths of the stream. As its favourite habitat is 
amongst the gravel of swift and mountain-fed streams, it is not 
surprising that the Tay is one of its principal stations in Britain. The 
varieties smuata and Roissyi both occur, and .^contorted specimens 
are not uncommon, caused, probably, by the motion of the stones in 
the current. Pearls, in all stages of development, are got in consider¬ 
able numbers by the pearl-fishers in summer, when the water is low. 
The occupation, however, is not so profitable as it was in former 
