CRUSTACEA OF NEW ZEALAND. 229 



as long as the joint is wide ; at tlie extremity are three long setae nearly as long as the 

 joint itself. 



The armatui'c of the right mandible differs from that of the left, as is the case in this 

 and many other genera of the Amphipoda. In the left mandible (fig. 6) the outer 

 cutting-edge consists of five strong teeth and the inner or secondary cutting-edge is 

 similar in general form but contains only four teeth, one of which is considerably longer 

 than the other three ; both outer and inner cutting-edges are curved so as to be concave 

 on the inner side. In the right mandible (figs. 7, 8) the outer edge is not unlike that 

 of the left, but contains only four teeth, and the inner cutting-edge is very different. 

 When seen in profile, as in figure 8, it appears slender, dividing into two branches 

 or forks, the upper one apparently tubercled, and the lower one bearing two or three 

 denticulations at its base ; in this view it seems not very unlike that of Gammarus 

 neglectiis as figured by Sars [91, pi. iv. fig. 4]. When this inner cutting-edge is seen 

 en face (fig. 7), however, it is found to be much more like that of Crangonyx eom- 

 pactiis than would at first have been suspected ; the upper portion proves to be broad 

 and triangular in shape, with the edge dentate, and it is these denticulations which make 

 the piece appear tubercled when seen in profile ; the loAver piece is narrow and bears one 

 or two teeth on the surface at its base as already described. 



Next to the secondary cutting-edge in each mandible follow four or five strong 

 denticulate or stiffiy plumose setae. The molar tubercle does not appear to present any 

 remarkable featui'e. 



The lower lip (fig. 9) is of the usual form, deeply cleft, each lobe bearing on its 

 rounded extremity a number of very fine irregular setse, and on its inner margin a thick 

 fringe of rather stouter setae. 



The first maxilla (figs. 10, 11, 12) has the inner lobe very dehcate and fringed with 

 nine or ten * delicate plumose setae, each of which shows a transverse division at some 

 distance from the base ; the surface of this plate is also covered with fine delicate 

 scattered setae. The middle lobe ends in about ten strong setae, curving inwards ; most 

 of them have two sharp teeth on the inner edge, but the two innermost bear more 

 numerous teeth. The palp has the first joint short, rectangular, and the second large, 

 flat, and curved inwards. On the left side (tig, 11) the palp ends in about seven stout 

 setae or spines, closely approximated together ; a single small simple seta is situated on 

 the surface at a slight distance from the extremity. In the maxilla on the left side 

 (tig. 12) the palp has the same general shape, but the setae at the end are much more 

 slender and not so crowded, and there appear to be only six of them. The difference 

 between the extremities of the two palps is really rather greater than would appear to be 

 th(! Ciise from figs. 11, 12, for the right maxilla is here considerably compressed in order 

 to show the spines more distinctly. 



The second maxilla (fig. 13) has the form usual in Gammarus. The inner lobe 



* Tho number of sctoe on the inner lobes of the first and second maxilla varies very greatly in different specimens. 

 The numbers given iu the text probably represent the average. I have another drawing showing I'd on the inner 

 lobe of the first maxilla and 21 on that of the second maxilla. 



30* 



