1236 THE VOYAGE OF H.M.S. CHALLENGER. 



on both sides with numerous short spines and occasional setules, and apically forms a 

 small tooth or projection, between which and the hinge of the finger it is crenulate, 

 the fringe of spines not being interrupted ; the finger is large, curved, acute, matching 

 the palrn. 



First Perseopods. — Attached a little behind the centre of the segment, which 

 is here a little dilated in the male, and greatly in the female. Branchial vesicles 

 narrow and elongate, about two-thirds the length of the limb. Marsupial plates much 

 longer and enormously broader than the branchial vesicles, in some specimens adorned 

 with numerous dendritic colour-spots. The limb extremely slender, and smooth ; the 

 first joint longer than the third and fourth together ; the second longer than broad ; 

 the third a little shorter than the fourth and fifth together ; the fourth and fifth 

 subequal ; each of the five joints having a setule at or near the apex of the hind 

 margin ; the finger more than half the length of the fifth joint, with convex front 

 margin, broad at the centre, the tip acute, near which the hind margin has a row of 

 about six small spines, the bases of which are broad. The relative proportions of the 

 joints vary to some extent with age and sex. 



Second Perseopods wanting. The branchial vesicles are attached at the centre of 

 the segment, which in the male is here very slightly dilated, while in the female as 

 usual the anterior part of the segment is broad, the posterior narrow; the branchial 

 vesicles scarcely so large as the preceding pair. 



Third Perseopods. — Attached behind the centre of the segment, small and degraded, 

 with only four distinct joints ; from the shape of the first of these it may be supposed 

 that it represents the second and third coalesced ; it about equals the length of the next, 

 or fourth joint ; the following or fifth joint is about equal to the two preceding united, 

 and is rather stouter, somewhat curved ; the finger is half the length of the preceding- 

 joint, strongly curved, acute. 



Fourth Perseopods. — Attached at the distal end of the segment, which is here dilated ; 

 the first joint elongate, like all the others except the second, distally a little widened, 

 rather longer than the fifth joint ; the second joint scarcely longer than broad ; the third 

 joint rather shorter than the fourth, widened a little distally ; the fourth subequal to the 

 fifth, having a spine near the base on the front margin ; the fifth joint having a pair of 

 spines near the base and several single spines along the course of the front margin and 

 some setules on the hind margin, the spines simple except for the accessory thread on the 

 outer side ; the finger curved, acute, as long as the fifth joint. 



Fifth Perseopods. — Attached at the distal end of the short seventh segment, 

 similar in general to the preceding pair, but the first joint much shorter, the fourth, 

 fifth, and finger considerably longer than in that pair. In the relative proportions of 

 these joints there is some amount of variation, whether it be from individual difference 

 or due to age or sex. 



