54 BRITISH COPEPODA. 



a vesiculiform swelling, the last joint hooked. Acces- 

 sory branch of posterior antenna (fig. 15) very small, 

 biarticulate ; mandible-palp (fig. 16) small, biarticulate, 

 unbranched, and bearing four small setae. First foot- 

 jaw (fig. 17) divided into four setiferous segments ; 

 second small (fig. 18) and forming a clawed hand. 

 The first four pairs of feet have both branches 3- 

 jointed ; the inner branch of the first pair (fig. 19) is 

 rather longer than the outer, its first joint being as 

 long as the second and third together, and having a 

 long seta and three or four small hairs on its inner 

 margin ; the inner branches of the second, third, and 

 fourth pairs are considerably longer than the outer, 

 and the outer margins of all are fringed with spine- 

 like hairs ; the third and fourth pairs longer than the 

 first two. Fifth pair in the female (fig 21) 2-jointed, 

 the basal joint short and broad, its inner segment 

 fringed with three short, equal spines, and two longer 

 ones, besides numerous short hairs ; the second joint is 

 sub-ovate, fringed with fine hairs and having five long 

 apical setae. In the male (fig. 22) the fifth pair is 

 obsolete, being reduced to a minute setiferous lobe. 

 Caudal segments very short, bearing two principal 

 setge, the outer half as long as the inner. Length - 2 - 7 -th 

 of an inch ('9 mm). 



This is a brackish-water species inhabiting the same 

 sort of localities as Tachidius brevicornis, from which, 

 however, it is perfectly distinct. I have taken it in a 

 large pond, subject to occasional tidal influx, at St. 

 Mary's (Scilly) ; in brackish pools by the River Stour, 

 at Manningtree, and in Oulton Broad (Suffolk) ; it 



