1282 THE VOYAGE OF H.M.S. CHALLENGER. 



fourth, about as long as the third, curved, pectinate, but not closely, on the concave 

 hind margin, the adjacent surface scabrous with little spines ; the finger narrow, curved 

 near the base, where on the inner margin it has a trace of incipient pectination, the length 

 not half that of the hand. There are some minute distant spinules on various parts of 

 the limb. 



Second Perseopods. — The side-plates deeper than the preceding pair. The branchial 

 vesicles and the limb similar to those of the first perseopods, but with the third, fourth, 

 and fifth joints of the limb longer. Both the first and second pairs of perseopods are 

 very considerably larger than the gnathopods. 



Third Perseopods. — The side-plates with a front lobe much broader than deep, and 

 a narrow hind lobe descending below the front one ; hexagonal markings are conspicuous 

 on these plates. The branchial vesicles broad, irregular in shape ; the marsupial plates 

 large. The first joint narrow at the base and nowhere much expanded, two or three 

 times as long as broad, the margins nearly parallel, the front one with four spines at the 

 distal part ; the second joint short ; the third joint longer than the fourth, shorter than 

 the fifth, rather narrower than the third joint of the preceding pair ; the fourth joint 

 has a small spine at the pectinate distal end, besides having like the two preceding joints 

 some minute spinules here and there ; the fifth joint is slightly curved and has the 

 concave front margin closely pectinate ; this and the preceding joint exceed in length 

 the corresponding joints both of the second and those of the fourth perseopods ; the 

 finger about a third of the length of the fifth joint. 



Fourth Perseopods. — The side-plates about equally broad and deep, the hind lobe 

 deeper than the front one. The branchial vesicles smaller than the preceding, but 

 otherwise very similar. The first joint wider and longer than in the preceding pair, 

 with five spines on the lower part of the front margin ; the third joint rather shorter than 

 in the third pair, with two spines at the distal end of the front margin ; the fourth joint 

 with the front margin pectinate except at the base, and carrying six spines at intervals, 

 the apical margin also pectinate ; the fifth joint armed as in the preceding pair ; the 

 finger similar. 



Fifth Perseopods very considerably shorter than the fourth, yet much more than half 

 the length. The side-plates rounded behind, and there free only for a short space from 

 the segment's upper part. The first joiut expanded, somewhat oblong, the front margin 

 not very convex, a little scabrous below, the hind margin very slightly convex, com- 

 pletely overlapping the short second joint with a narrow rounded lobe ; the third joint 

 bent forward at the base, the proximal part of the hind margin being convex, the rest 

 straight, having a small spine near the apex, and having like the other joints some 

 pectination of the distal margin ; the front margin nearly straight, with a small apical 

 spine ; the fourth joint longer than the third, slightly curved ; the fifth joint narrower 

 but rather longer than the fourth, also slightly bent ; the finger not acute, shorter than 



