REPORT ON THE CUMACEA. 37 



cavities. During the rhythmical movements of the epipodite-plates, this tube remains 

 immovably exserted, but is immediately withdrawn when the movements are 

 interrupted. 



The first pair of gnathopoda (fig. 16) do not exhibit any peculiarity in their 

 structure. 



The second pair of gnathopoda (fig. 17), on the other hand, exhibit a form rather 

 different from that in most other Cumacea. Thus, the basal part is rather broad and 

 only very slightly longer than the terminal part. It has several ciliated bristles along 

 the inner edge, and from its external corner four very strong anteriorly curving setse 

 originate, the outer of which especially is of quite unusual size and densely ciliate. 

 The terminal part is provided with comparatively short bristles, with the exception of 

 its second joint, which has externally a strong anteriorly curving seta similar to those 

 arising from the outer corner of the basal part. The exopodite is rather powerful, with 

 the basal part compressed, oblong, and the terminal composed of five articulations. 



The first pair of legs (fig. 18) are about equal in length to the carapace and the two 

 anterior exposed segments of the trunk taken together, and are rather slender, tapering 

 gradually from the base to the tip. The basal joint is, as usual, somewhat dilated in its 

 proximal part, where it contains the strong muscles moving the exopodite, and is 

 fringed along almost the whole inner edge, and the distal part of the outer, with 

 ciliated bristles ; moreover, a row of short spines occurs along the distal part at some 

 distance from the outer edge. The terminal part of the leg is much longer than the 

 basal, and is furnished with scattered plumose setae, especially along the outer edge. Of 

 the joints the antepenultimate and penultimate are the longest and about equal in size. 

 The last joint is slightly compressed but rather narrow, and armed at the tip with about 

 six strong, claw-like spines. The exopodite has much the same appearance as that of 

 the second pair of gnathopoda, except that its terminal part has one joint more. 



The second pair of legs (fig. 19) are much shorter than the first, but rather stout, 

 with the basal and terminal parts about equal in length. The ischial joint seems to be 

 quite wanting. The meral joint is rather thick and armed at the end on the inner side 

 with a strong spine. The carpal joint is about twice as long, but much narrower, and 

 has a similar, though somewhat smaller spine at the end. The propodal joint is quite 

 short and unarmed, whereas the terminal is rather elongate, linear, and furnished with 

 numerous stiff spine-like bristles, forming a spreading bunch at the end of the joint. 

 The exopodite does not differ from that of the first pair of legs. 



The third pair of legs (fig. 20) in both sexes are furnished with well-developed 

 natatory exopodites. The basal part of the endopodite is more than twice as long as the 

 terminal, and, as in the two preceding pairs, rather dilated to receive the strong 

 muscles moving the exopodite ; along both edges there are a number of ciliated setse. 

 Of the joints composing the terminal part, the three first slightly increase in size, and 



