AMPHIPODA OF THE BRITISH ISLES. 149 
Terminal uropoda in the fully-grown male nearly one-half the 
length of the body ; outer ramus of two subequal joints, the first 
with four tufts of sete, the terminal one nearly free from sete, 
except a small tuft at the apex. In the female the terminal 
uropoda one-fourth the length of the body, and the last joint 
of outer ramus only about one-third of the first. 
Telson reaching to the end of the peduncle of the third uro- 
poda, split to more than half its length, each lobe narrowing 
towards the apex, which bears three stout sete; outer margin 
convex, and with two fine set a little anterior to the apex. 
Length of fully-grown specimens about 11 mm. 
Habitat. Southern Counties of England ; (Europe generally). 
The above description will, I hope, be sufficient fur the identi- 
fication of this species. A much more detailed description is 
given by Humbert of Mphargus puteanus var. Forelii, from 
Lake Geneva. Wrzesniowski indeed thinks this form sufficiently 
distinct to rank as a separate species, WV. Forelii; but though he 
is perhaps right, the differences are very slight. Wrzesniowski’s 
full description of Miphargus puteanus var. Vejdovskyi may also 
be consulted. 
The points chiefly relied upon by Wrzesniowski for the sepa- 
ration of the different species of Niphargus are the lengths of 
the antennz and terminal uropoda in proportion to the body, the 
depth of the side-plates, the relative lengths of the pereiopoda, 
the shape of the propoda of the gnathopoda and of the lower 
margins and angles of the first three segments of the pleon, and 
the relative lengths of the two joints of the outer ramus of the 
third uropod. These points he found to be fairly constant in 
specimens of different ages from the same locality ; and they no 
doubt are good specific characters, though it is a little difficult to 
estimate some of them with accuracy, and I am inclined to think 
that Wrzésniowski relied a little too much on the supposed 
accuracy of the descriptions and figures given by other writers. 
It must be remembered, too, that the relative lengths of the 
two joints of the outer ramus of third uropoda varies in the two 
SeXes. 
In addition to these points, I have found the shape of the 
maxillipedes and of the more proximal joints of the gnathopoda, 
especially the basos and the carpus, useful points for distinguishing 
the British species; while the number of sete arising from 
the outer margin of the dactylos is a character that may be 
useful for readily separating some species, such as J. tatrensis, 
