414 MR. ROBERT GURNEY ON THE CRUSTACEA 
at the time. They show that the fauna is mainly of a marine 
type irrespective of the state of the tide, but that fresh-water 
species may be brought down on the ebb, though they do not 
form a normal component of the fauna. I suppose that many 
individuals of the fresh-water floating species must be carried 
into salt water and killed, for it is not uncommon to find 
dead specimens of fresh-water species in a collection. Such 
a destruction, if it occurs, would not however, be of any 
great importance, since I believe that the rivers do not have 
what may be called an indigenous fauna of floating species. 
I believe that the stock is maintained by constant influx 
from breeding centres in the still water of the Broads. 
Proceeding further up the river one finds the fresh-water 
element more in evidence, collections containing solely marine 
species being the exception. Here are some examples : — 
(1) Just above Yarmouth. 
June 21st, 1906. 5.15 p.m. ebb. 
Ceriodaphnia pulchella. 
Bosmina longirostris. 
Chydorus sph.ericus. 
Cyclops leuckarti. 
Tachidius brevicornis. 
Loxoconcha viridis. 
(2) Between 6 and 5-mile House. 
April 27th, 1903. High water. 
Bosmina longirostris. 
SlMOCEPHALUS VETULUS. 
Chydorus sph^ericus. 
Cyclops strenuus. 
,, LEUCKARTI. 
Eurytemora lacinulata. 
,, AFFINIS. 
Tachidius littoralis. 
,, brevicornis. 
COROPHIUM GROSSIPES. 
Heterotanais GURNEYI. 
Neomysis vulgaris. 
