IN THE NORFOLK BROADS DISTRICT. 
75 
Thus Haliplus obliquus, which showed its best record in 
the Muck Fleet district, showed its second best record in the 
Coast district, its third best in Palling district, and so on. 
It is interesting to notice that out of the thirteen species 
showing their best record in the Muck Fleet district, five 
show their second best in the Bure district, four in the Coast 
district, and one each in the Ant, Ormesby, and Hickling 
districts. 
If in the same way we separate out the species with their 
best record of occurrences in the Coast district we shall find 
that of the eleven species, four have their second best record 
in the Muck Fleet district, two in Palling, one each in 
Ormesby and Hickling, while three species occur nowhere 
else. If once again we separate out those species with their 
best record in the Bure district we find that of the nine 
species three have their second best record in the Muck Fleet 
district, two in the Ant, two in Ormesby, one in Hickling, 
and one in the Coast district. 
Thus there is apparently a relationship between the aquatic 
Beetle fauna of the Muck Fleet and Coast districts on the one 
hand and between the Muck Fleet and Bure districts on the 
other. 
If we further examine the percentage of occurrences of 
the species in the various districts we shall find that there is 
a similar relationship between the Ant and Ormesby districts, 
the Ant and Hickling districts, the Ant and Bure districts, 
and so on. 
Now how can such relationships be accounted for ? Where 
two districts lie next one another, as in the case of the Ant 
and Hickling districts, it is perhaps natural that the faunas 
should to some extent overlap, but such an explanation cannot 
account for the relationship between the Muck Fleet and 
Coast districts or between the Ant and Ormesby districts. 
I think that in a general way explanation is possible. 
Taking the case of the Muck Fleet district, I have already 
mentioned that it is within reach of the salt water, of which 
it occasionally gets plenty. This saltness, occasional though 
it be, may perhaps account for the presence of such species as 
