AND At SEAtON SLUICE, NORiaUMSERLAND. 25 



stout in proportion to the length, only slightly tapered, joints 

 nearly equal in length throughout : each joint bears one or more 

 short and rather stout setse, but there is no special sensory seta. 

 Antennae two-jointed ; secondary branch consisting of one small 

 joint only, with three or four small terminal setse. Outer branch 

 of the first pair of swimming feet three- jointed, the last joint 

 very small and ending in three slender setse, two of which are 

 extremely long, the third and outermost being haK as long as 

 the rest, which are about thrice the length of the entire limb, 

 including the protopodite : the first and second joints have each 

 a long, stout spine and several small hairs on their outer margin ; 

 the second has also a single short seta on its inner margin: 

 inner branch two- jointed, only a little shorter than the outer 

 branch, its first joint bearing only a few short hairs on the outer 

 margin, second joint equal in length to the first, but more slen- 

 der, bearing at the apex two long and two very short eetse, and 

 on the inner margin a single short seta : the second joint of the 

 protopodite carries at the inner distal angle a stout curved spine 

 which reaches as far as the middle of the second joint; and on 

 its outer margin one much shorter spine. The second, third 

 and fourth swimming feet are alike, having the inner branch of 

 one, the outer of three joints ; the first and second joints of the 

 outer branch bear each a long and rather stout apical spine and 

 a fringe of shorter spine-like hairs on the outer margin; the 

 last joint has three apical setse decreasing progressively in length 

 from the innermost, which is longer than the entire limb ; each 

 of the three joints has also a minute seta at the internal apex; 

 the inner branch is shorter than the first joint of the outer 

 branch and has three terminal setse, the central one about twice 

 as long as the other two, which are subequal : it has also a few 

 small marginal cilia externally. The fifth foot is almost rudi- 

 mentary, the basal portion very short but wide, its internal 

 portion fringed with four nearly equal ciliated setae, its outer 

 portion giving attachment at the outer angle to a long seta and 

 to a single laminar joint, from which spring four unequal ciliated 

 setae. The head is coalescent with the first thoracic segment, 

 the united lengths of the two being equal to about one-fifth of 



