202 Messrs. T. and A. Scott on some new or rare 



short but stout and strongly hooked spine and four small 

 setse (fig. 3). A short trumpet-shaped siphon, capable of 

 being extended or depressed, is situated nearly between the 

 bases of the posterior antennae, as shown in tig. 4 c (see also 

 fig. 5). The otlier mouth-organs are nearly as in Licho- 

 moJgus forficida^ Thorell, except tliat the mandible has no 

 fringe of hairs on its upper margin and a ])rominent spiniform 

 seta springs from the basal part of the anterior foot-jaw 

 (figs. 6 and 7). The posterior foot-jaws differ considerably 

 in the two sexes : those of the male are armed with extremely 

 long and powerful falciform terminal claws, which are pro- 

 vided with a small spiniform seta at their base ; the upper 

 margin of the proximal half of the last joint is fringed with 

 small teeth, and a spiniform seta springs from each side and 

 near the middle of the same joint : the female foot-jaw, 

 which gradually tapers towards the extremity, terminates in a 

 short and stout claw, about half as long again as the joint 

 from which it springs (fig. 9). The first four pairs of 

 swimming-feet have both branches three-jointed ; the last 

 joint of the outer branch of the first pair is furnished with 

 four dagger-shaped spines on the outer margin, the subter- 

 niinal spine being longer than the others ; the last joint of 

 the outer branch of the fourth pair has one dagger-shaped 

 terminal spine and two on the exterior margin ; the last joint 

 of the inner branches also bears dagger-shaped spines, and the 

 inner margins of both branches are clothed with elongate 

 plumose hairs ; the spines and plumose hairs of the last joint 

 of the inner branches of the four pairs are arranged in the 

 following order : — in that of the first pair there are five hairs 

 round the inner margin and end and one dagger-shaped spine 

 on the exterior margin ; that of the second pair has three 

 hairs on the inner margin, two spines on the outer margin, 

 and one terminal spine; that of the third pair has two hairs 

 on the inner margin and three spines arranged as in the 

 second pair ; in that of the fourth pair there are no hairs on 

 the inner margin, but there are two elongate spines, one 

 terminal and one subterminal (figs. 10 and 11). The fifth 

 pair in both sexes are small and provided with two terminal 

 setse, one being moderately long and slender and one stout 

 and spiniform (fig. 12). Abdomen elongate, composed in the 

 female of four, in the male of five segments : the first segment 

 in both sexes is large and tumid, the greatest breadth of this 

 segment in the female is near the middle, but in the male it 

 is broadest at the distal end ; the postero-lateral angles of 

 this segment in the male are each furnished with two small 

 setffi ; the remaining segments are comparatively small and 



