MR. R. GURNEY ON FRE8II- AND BRACKISH- WATER CRUSTACEA. 653 
being probably due to salt springs. The great rise of salinity 
found on proceeding from Heigham Sounds to Horsey Mere can 
only be explained in this way, and there are probably similar, 
though smaller, springs in Hickling. Martham Broad probably 
owes its saltness to a sort of reflux of the Horsey and Hickling 
water xip the Thurne. As a consequence of this high salinity we 
find the whole group characterised by the presence of Neomysis 
vulgaris and Gammarus duebeni in great abundance. The Entomo- 
stracan fauna, very poor in species in Horsey Mere, becomes richer 
in Hickling and Heigham Sounds, and is richest in Martham 
Broad, which is the least salt of all. The scarcity of species, 
however, is compensated for by a great abundance of individuals. 
Unfortunately, I have not been able to give the Broads of this 
group the attention they deserve, so that my list for them is incom- 
plete. For instance, I have no record of Tachidius littoralis from 
Horsey Mere, but I have little doubt that it actually occurs there, 
and also in Hickling. The botany of this group deserves more 
detailed attention than it has yet received ; in no other Broads is 
there such a rich growth of Cliaracew and of certain species of 
Potamogeton. It would be exceedingly interesting to know if the 
species of these plants show any dependence upon salinity, whether 
as regards their distribution or the luxuriance of their growth. 
The next natural group is formed by Sutton and Barton Broads 
and Catfield Fen. This group is not so homogeneous as the first, 
but its three components possess certain characters in common, 
which makes it convenient to unite them. They differ as a whole 
from the Broads of the Bure in their relatively small area of open 
water, and the consequent absence, except as rare stragglers, of the 
pelagic species of Daphnia. They resemble each other in the 
richness of their vegetation, to which is perhaps due the richness 
of their Crustacean fauna. All three are rapidly “growing up”; 
in fact Catfield Fen, which consists of a number of large peat 
holes, now has very little open water indeed. Barton Broad, 
however, shows more or less of a transition, at all events in its 
general appearance, towards the open Broads of the Bure. It has 
been suggested by Mr. H. B. "Woodward that this Broad is 
artificial, owing its existence (as Catfield Fen does) to peat-cutting. 
The present depth of the water seems very much against such 
a view, and I cannot believe that the arm which runs up towards 
