416 MR. ROBERT GURNEY ON THE CRUSTACEA 
constantly of a somewhat higher salinity than that of the 
fresh- water Broads, is not subject to distinct fluctuations of 
salinity dependent upon the tides. Generally, in this section, 
one expects to find the floating fauna of a prevailing fresh- 
water type though with a small proportion of Algal con- 
stituents, while there is also a rather extensive sedentary 
population, subject of course to variation, comprising species 
commonly considered as brackish or marine. The water has 
here lost the turbid character of the lower reaches which seems 
inimical to life. Of sixteen series of collections made within 
this area eleven may be said to contain predominant fresh- 
water forms and five salt or brackish species. I give here 
three lists of species representing these opposite conditions. 
An analysis of the relations of the species one with the other 
will be given below. 
(if July 6th, 7th, 1906. 
Between Muckfleet and Acle Bridge. 
Chlorine 7.34 gr. per gall. 
Nereis diversicolor. 
CORDYLOPHORA LACUSTRIS. 
SlDA CRYSTALLINA. 
DlAPHANOSOMA BRACHYURUM. 
Ceriodaphnia quadrangula. 
SlMOCEPHALUS VETULUS. 
SCHAPHOLEBERIS MUCRONATA. 
Bosmina LONGIROSTRIS. 
Ilyocryptus agilis. 
Eurycercus lamellatus. 
Lynceus affinis. 
„ QUADRANGULARIS. 
Chydorus sphaericus. 
Cyclops viridis. 
,, LEUCKARTI. 
,, SERRULATUS. 
Taciiidius LITTORALIS. 
LaOPHONTE MOHAMMED. 
Eurytemora lacinulata. 
