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MR. ROBERT GURNEY ON THE CRUSTACEA 
XI. 
THE CRUSTACEA OF THE EAST 
NORFOLK RIVERS. 
By Robert Gurney, B.A. 
Read 26 th February, 1907. 
In my account of the Crustacea of East Norfolk, published 
in our Transactions in 1904, I concerned myself more par- 
ticularly with the fresh-water forms, though a certain number 
of species were included which had been met with in brackish 
water. It was evident that much fuller information was 
required concerning the fauna of the rivers, particularly of 
those parts of them which are subject to tidal influence. 
I have, therefore, when opportunity has offered, endeavoured 
to make a beginning in this direction. The results, incomplete 
as they are, seem to me of sufficient interest to communicate 
to you now. The difficulties to be met in studying the fauna 
of the tidal regions of the rivers are naturally very much 
greater than those encountered in studying their upper 
reaches and the Broads. These difficulties are partly practical 
and partly theoretical. The practical difficulties are due to 
the fact that one has to deal more with Crustacea of a higher 
order, more active and more difficult to find. I have tried 
a variety of methods, using, in the first instance, hand nets 
with large and small mesh. The most active species, such as 
Pakemonetes, have been caught in traps made on the principle 
of a crab pot baited with bacon, and let down in the river. 
The sedentary species of Isopoda and Amphipoda must be 
searched for very carefully on submerged wooden posts, 
under stones and in mud. What I call the theoretical diffi- 
