420 MR. ROBERT GURNEY ON THE CRUSTACEA 
brackish Copepoda sometimes find their way in. The follow- 
ing collections show the nature of the fauna. I also give a 
table showing the whole list of species hitherto found here 
and the species with which each may associate. 
In this table the species are numbered 1-27 and the numbers 
are repeated at the heads of the columns so that each has 
a line and a column to itself. When analysing any collection 
a cross is put in the column corresponding to each species 
opposite the names of the other species in the collection. 
In this way one arrives at a statement of all the species with 
which any one has been found associated. Taking the 
column corresponding to any species the associates of it can 
be read off by reference to the crosses. The table shows that 
there is a rather more complete mixing of fresh-water species 
with brackish species than obtains as a rule in the river. 
I attribute this to the favourable conditions of stillness and 
vegetation somewhat counterbalancing the effect of salinity. 
Still, it can also be seen that the fauna was relatively poorer 
during periods of salt water than when the water was fresh. 
The two collections given below show that there is normally 
a fresh-water fauna, modified by the presence of Gammarus 
duebeni, which indicates a salinity rather higher than that 
of pure fresh water ; but that, during periods when the salinity 
rises to a high point, the fresh- water fauna becomes poorer 
and brackish species appear in addition. 
(1) September 23rd, 1903. 
Chlorine 235 grs. per gallon. 
Bosmina longirostris. 
Lynceus rectangulus. 
Eurytemora lacinulata. 
Cyclops bicuspidatus. 
„ var. lubbocku. 
„ VIRIDIS. 
,, SERRULATUS. 
,, .EQUOREUS. 
Tachidius littoralis. 
LaOPHONTE MOHAMMED. 
Gammarus duebeni .' 1 
