916 THE VOYAGE OF H.M.S. CHALLENGER. 



and at the margins, and at the apex a graduated row of strongly pectinate spines ; the 

 finger short and broad, with a sharp nail having a cilium at its base ; the inner margin 

 of the finger smooth near the base, then set with eight setules ; in the small specimens 

 there are fewer spine-teeth on the outer plate, and fewer setules on the edge of the 

 finger. 



First Gnathopods. — Side-plates rounded below, First joint reaching much beyond 

 the side-plate, the front margin straight, with small setse, the hinder with some long and 

 short setse near the base and a group of spines at the apex, some of them pectinate ; the 

 second joint short, with spines at the apex behind ; the third joint rhomboidal, with 

 spines on the hinder and lower margins, the front margin apically produced ; the wrist 

 shorter than the hand in the young and female, very much shorter in the adult male, with 

 numerous distally pectinate spines about the free portion of the hind margin, which is 

 somewhat serrate ; the hand in the adult male broader than the wrist, widest at the palm, 

 with six groups of spines along the straight hind margin and several small groups on the 

 inner surface ; the palm convex, a little oblique, fringed with setules, a row of five or six 

 broad spines of different lengths on the surface on either side of it ; the curved finger 

 when closed shows its tip just beyond the palm ; it has some spinules or teeth on the 

 inner edge and a small dorsal cilium not very far from the base. 



Second Gnathopods. — Side-plates oblong, with rounded ends, deeper than the preceding 

 pair. Branchial vesicles long and of great breadth, narrowing little distally. Marsupial 

 plates very long and broad, narrowing distally, with many long setse round the distal end 

 and inner margin. The limb closely resembles that of the first gnathopods, but with the 

 first, third, fourth, and fifth joints more elongated ; the apical spines on the hind border 

 of the first joint show the same pectination. Both the first and second gnathopods of 

 the male specimen examined were beset with a parasitic zoophyte in great number ; their 

 appearance on the first joint of the first is figured PI. LXXV. fig. gn.\. $ . In both 

 gnathopods the hand is very much narrower in the young and female than in the male. 



First Perasopods. — Side-plates like the preceding pair but larger. Branchial vesicles 

 with a narrow neck, then gradually expanding and again narrowing slightly, very long. 

 Marsupial plates broad, even distally, longer than the branchial vesicles, with long setse all 

 round, sparsely on the outer side. First joint of the limb reaching beyond the side-plate, 

 with short spines along the straight front margin, some long setse on the hinder margin 

 and groups of spines ; a group of spines on the hinder apex of the second joint ; several 

 groups on both margins of the third joint, which is broader than the fourth or fifth, longer 

 than the fourth, but subequal in length to the fifth, its front apex somewhat decurrent ; 

 the fourth and fifth joints have numerous groups of spines on the hinder margin, while 

 the front margin is slightly armed ; the finger is short, curved, with a small dorsal cilium 

 near the base, and two cilia at the base of the nail. 



Second Perteojiods. — Side-plates much broader but very little deeper than the pre- 



