BY GEO. M. THOMSON, F.L.S. 53 



"branch, wliicli is both smaller and more rounded, being 

 fringed with short plumose setse. The second maxilhi^, are 

 four-branched, each branch being one-jointed. These two 

 pairs of organs appear to be purely masticatory in their func- 

 tion and to differ from those of other Schizopods, not only 

 in the number of their articulations, but also in the total 

 absence of any external appendages. The maxillipeds are 

 similar in general form to the succeeding pairs of legs. Thej 

 are very distinctly seven-jointed, and bear on the inner side of 

 the coxal joint two small lamellar organs fringed with setse, and 

 which appear to act as masticatory lobes subsidisary to the 

 maxillse. These resemble in a more highly developed form 

 tlie masticatory lobe found on the corresponding joint on the 

 maxilliped of most species of the Euphausiidse. On the 

 outer side of the coxa are two small lamellar branchiae, while 

 tlie basos bears a short slender one-jointed exopodite which 

 just shows at its extremity traces of the articulation which 

 characterises the same organ in the succeeding appendages. 

 The dactylos of this limb (and of nearly all the succeeding 

 pairs) ends in two or three powerful hooked claws which are 

 almost hidden among setse. 



The other seven pairs of walking legs increase in length up 

 to the fourth, which is the longest, and then gradually de- 

 crease in length and robustness to the last. The branchise, which 

 greatly resembles tlie same organs among ordinary amphipod 

 crustaceins, undergo a somewhat similar progression and 

 diminution in size, but are quite wanting on the last ^^air. 

 The exopodites or natatory branches increase in size rela- 

 tively to the limbs which bear them from the first up to the 

 sixth pair, in the seventh they are reduced to small branchia- 

 like processes, quite destitute of segmentation, in the eighth 

 they are quite wanting. 



The five pairs of j^leopoda are all similar in form in the 

 females. Each consists of a basal joint can-ying a large 

 natatory exopodite near its outer angle, and a small lamellar 

 endopodite, like a rudimentary gill, on its inner angle. In 

 the males the endopodite of the first pair is developed into a 

 lamelliform plate, j^rojecting inwards and apparently fur- 

 nished with a duct, while the corresponding limits of the 

 second pair are produced into two scoop-like processes, with 

 their hollow faces meeting in the median line. I have not 

 discovered the use of these organs. The sixth j^air or uropoda 

 are developed into a large tail-fin as in most Schizopods, but 

 owing to the shortness of the telson this is formed of four 

 (not five) plates. The plates are sub-equal in length, narrow- 

 oblong in form, and are fringed with long comb-like setae. 

 The outer plates are ridged on their outer proximal margins, 

 and are partly divided by a transverse ridge defined by a row 



