Sunaristes paguri, Hesse. 491 
of the third joint (PJ. XIT. fig. 5) ; these prolongations, espe- 
cially those of the first joints, are, like the terminal claws of 
the antennules, of a brownish colour. The first two somites 
of the male abdomen are not coalesced as in the female, and 
therefore the male has five abdominal segments; the first 
segment being of somewhat greater depth than the next ono, 
extends beyond it on the underside. ‘The first body-segment 
in the male is proportionally rather more robust than the same 
segment in the female, but in other respects male and female 
are much alike in general appearance (Pl. XI. fig. 9); the 
male specimen represented by fig. 9* measured fully 2 millim. 
(z5 of an inch) in length, exclusive of tail-sete, being about 
one third shorter than the female. 
Remarks.—It is evident from the foregoing description 
that there is a considerable resemblance between the two 
genera Sunaristes and Canuella and, in some respects, 
between these and Longipedia; the antennules, antenne, and 
the whole of the mouth-organs of the females in the three 
genera are all nearly alike; the same may to some extent be 
also said of the males; moreover, the swimming-feet of the 
females belonging to the three genera (with the exception of 
the second and fifth pair in Longipedia) are all very similar ; 
but though the three genera Sunaristes, Canuella, and Longi- 
pedia, and especially the first two, resemble each other so 
closely in many of their structural details, there are also the 
following important differences to be observed :—The female 
Sunaristes differs from the females of Canuella and Longi- 
pedia in having the first two somites of the abdomen com- 
pletely coalesced. The female Longipedia differs from the 
female of Sunaristes and Canuella in having the inner 
branches of the second pair of swimming-feet greatly elon- 
gated, being from two to nearly three times the length of the 
outer branches (in the male of Longipedia the inner branches 
of the second pair are also elongate). The male Sunaristes 
differs from the male of Canuella and Longipedia not only in 
possessing more powerfully armed antennules, but also in the 
peculiar prolongations of the first and second joints of the 
inner branches of the second pair of swimming-feet. The 
male of Canuella differs from the male of Sunaristes and 
Longipedia in having both branches of the second pair of 
- swimming-feet short and similar in structure to those of the 
female. On the other hand, Longipedia differs from the other 
two in the form of the fifth pair of thoracic feet in both sexes. 
* This specimen was obtained near the mouth of the River Mersey. 
It would thus seem that Swnuristes is partial to brackish water con- 
ditions. 
ition 33% 
