OF THE EAST NORFOLK RIVERS. 
423 
Hickling Broad and in Horsey Mere where the salinity is 
highest. Palcemonetes varians is to be found at Potter 
Heigham, but has not been taken further up. There seems 
to be no reason why it should not occur also in the Broads 
themselves since, in a trap set in Heigham Sounds on June 
8th, 1906, a single specimen of Palcemon squilla was caught, 
together with a specimen of Hydrophilus piceus. CoropJiium 
grossipes also occurs in Heigham Sounds in colonies of Cordy- 
lophora, and is probably to be found all along the river from 
Candle Dike downwards, wherever Cordylophora occurs. 
The Yare and the Waveney. 
So far as concerns their Crustacean Fauna the Yare and 
Waveney resemble the Bure very closely, but, from lack of 
extended observations, I cannot deal with them in detail. 
So far as my experience goes, it appears that the floating 
marine species do not reach, as a rule, even as far as Reedham 
on the Yare or St. Olaves on the Waveney. The plankton 
of the rivers above those points consists almost exclusively 
of fresh-water species. The conditions at Cantley — about 
12 miles from Yarmouth — seem to resemble those at Acle on 
the Bure. That is to say, the fauna consists of fresh-water 
species with which are associated certain brackish-water 
species capable of adapting themselves to fresh water. 
In the Waveney the subject is somewhat complicated by 
Oul ton Broad. There is a considerable influx of salt water 
into the Broad through Mutford Lock, since boats come 
through the lock on high water from Lake Lothing. The 
effect varies according to the traffic, but it may be so great 
that Oulton Broad may become, so far as concerns its Crus- 
tacean fauna, merely an extension of Lake Lothing. Some 
of the salt water no doubt finds its way into the Waveney 
and so tends to cause a uniform high salinity from this point 
downwards. 
Lower down both rivers, at Berney Arms and by Burgh 
Castle respectively, there is a rich sedentary estuarine fauna. 
Some of the species common here are also found abundantly 
