OF THE EAST NORFOLK RIVERS. 415 
These collections do not give quite a fair idea of the fauna, 
since one of them (No. i) was taken with a townet and thus 
did not contain species which were almost certainly present, 
for example, Neomysis vulgaris and Palcemonetes varians. 
The following is a list of species taken at a point between 
Runham and Stokesby on August 19th, 1906, during a high 
salt tide. 
Noctiluca miliaris. 
Hormiphora sp. 
Acartia discaudata. 
Centropages hamatus. 
Eurytemora affinis. 
Balanus nauplii. 
Sph.eroma rugicauda. 
Gnathia maxillaris. 
Leptocheirus sp. 
Macromysis flexuosa. 
Neomysis vulgaris. 
Macropsis slabberi. 
Pal.emonetes varians. 
Of course such an exclusively marine fauna is exceptional 
in the upper parts of this section. An additional proof of 
this is that the fauna of the ditches adjoining the river behind 
the river walls is exclusively fresh- water. In the truly 
estuarine parts of the river the salt water makes its influence 
felt even upon the surrounding marshes. 
Section II. — Six-mile House to Acle Bridge. 
This Section, which covers a stretch of about five miles of 
river, is perhaps the most interesting of all. It is essentially 
a region of transition from salt to fresh water, for, whereas 
at the one end the estuarine features can still be traced, 
at the other end one finds oneself even more distinctly within 
the fresh-water sphere. From about Stokesby upwards one 
finds Reeds and Sedges along the bank, and sometimes, in 
sheltered nooks, a good deal of Potamogeton and other weeds. 
In normal circumstances the water at Acle Bridge, while 
