Sunaristes paguri, Hesse. 491 



of the tliird joint (PI. XII. 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 one, 

 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 (PI. XI. fig. 9) ; the 

 male specimen represented by fig. 9* measured fully 2 millim. 

 (^^2 of an inch) in length, exclusive of tail-setse, 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, antennae, 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 Irom 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 Sunaristes is partial to brackish water con- 

 ditions. 



