AMPHIPOD GENUS LEPTOCHEIRUS. 567 



in the male. In the female (fig. 11) the hand is shorter than the 

 preceding joint and lies in the samie plane with it, but in the male 

 it is a quarter as long again as the 5th joint, and is carried bent 

 at right angles to it (fig. 1 2). The finger differs also : in the 

 male it is much stouter, more curved, and with a depression 

 in the inner margin proxiinally. The long 2nd joint is fur- 

 nished with a cluster of long delicate setae on the posterior 

 margin, and a row of short plumose setae on the anterior margin, 

 with another row of longer similar ones on the inner surface. 

 3rd joint bulging behind ; 3rd and 4th fringed posteriorly with 

 long plumose setfe ; 5th joint with transverse rows of plumose 

 sette, and 4 fan-like clusters of rigid serrate bristles on the 

 posterior margin. These bristles (fig. 15) are found on the 5th 

 joint of the first gnathopod in all the species of the genus. The 

 6th joint or hand is subequal to the 5th in length in the imma- 

 ture specimen (fig. 10) ; distally widened ; palm slightly oblique ; 

 palmar margin microscopically pectinate, palmar angle with a 

 row of spines on the oxiter side, and 1 large spine on the under 

 side, with the tip of the finger fitting between them. The outer 

 row consists of 6 graduated slender spines, the first much the 

 longest, the shafts of which are produced apically into two unequal 

 processes, with a flat, delicate, feathered end-piece betAveen the 

 processes. In one specimen there were 6 on one gnathopod and 

 7 on the other. On the inner side of the palmar angle a very 

 large stout sensory spine is inset, accompanied by 4 short stumpy 

 bristles similar in construction to those of the outer row. A row 

 of these stumpy bristles is found submarginally on the under 

 surface of the palm, and 3 or 4 rather larger ones on the outer 

 side. The finger in the young (fig. 10) is stout and curved, as 

 long as the palm, also microscopically pectinate, with a short 

 decurrent tooth near the apex, 2 setae inset in the notch, 1 

 smaller tooth behind, and 1 setule proximally. The full develop- 

 ment of the finger of the female is shown in fig. 13 and of the 

 male in fig. 14. 



Second (gnathopod (figs. 16-18). — 2nd joint very long, laminar, 

 with two rows of exceedingly long plumose setae anteriorly, 

 one marginal, and the other submarginal on the under surface ; 

 posterior margin with only 3 or 4 long simple setje. A chitinous 

 ridge extends diagonally across the distal half of this joint, and 

 terminates at the posterior angle of the 3rd ; this appears to be 

 the " crista " referred to by Zaddach (" in superficie externa 

 crista quadam a basi secundi articuli ascendente"). The 4th, 5th, 

 and 6th joints are practically subequal to each other in length ; 

 distal margin of the 4th joint Avith very long plumose setae on the 

 under side ; posterior margins of the 5th and 6th with fan-like 

 clvisters of short, stifi", finely serrated setae, anterior margins Avith 

 long plumose seta?, the number of Avhich increases a little with 

 growth, the smallest specimen having 9 on the 6th joint and 

 the largest 11, 3 on the 5th joint in all specimens. The 

 6th joint is slightl}'^ narrowed distally. The finger is almost 



