OF THE EAST NORFOLK RIVERS. 
421 
(2) July 5th, 1906. 
Water fresh. 
Ceriodaphnia pulchella. 
SlMOCEPHALUS VETULUS. 
Chydorus sph.ericus. 
Eurytemora lacinulata 
Cyclops leuckarti. 
„ VIRIDIS. 
,, SERRULATUS. 
,, PRASINUS. 
Thersites GASTEROSTEI. 
Argulus foliaceus. 
Gammarus duebeni. 
CORDYLOPHORA LACUSTRIS. 
Section III. — Above Acle Bridge. 
Above Acle Bridge it is unnecessary to deal with the river 
in sections. Beyond this point the influence of salt water is, 
as a rule, almost negligeable so far as concerns the Bure and 
Ant. Below South Walsham the floating fauna is generally 
deficient with regard to certain species characteristic of pure 
fresh water, e.g., Daplinia cucullata — and one rarely finds any 
considerable quantity of floating Algce and Diatoms. Also 
such species as Eurytemora affinis and Tachidius littorcdis are 
generally to be found. Up to this point it is also possible 
to find occasionally species which show an even more distinct 
marine origin : for I have found, nearly opposite South Wals- 
ham Dike, Corophium grossipes, Hcterotanais gurneyi, aiid 
Palcvmonetes varians. Still, the presence of these species 
indicates only their own adaptability and not salt-water 
conditions. So far as my own observations go this is the 
normal limit of the range of Eurytemora affinis and Tachidius 
littoralis, which are the most adaptable of the brackish 
Copepoda. Stragglers are sometimes taken even further up, 
both having occurred in fresh water in South Walsham and 
Ran worth Broads and at Ludhain Bridge. Eurytemora 
affinis has actually been caught in Barton and Sutton Broads ; 
