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



excavation, from which the margin runs obHquely forward, closely fringed with setae 

 and continuous with the convex lower margin. The limb similar to that of the first 

 peraeopods. 



Third Perseoiwds. — The side-plates broad, with the two lobes almost equal. The 

 branchial vesicles seemingly not quite so large as those of the preceding pair. The 

 first joint broadest above, nearly once and a half as long as broad, with numerous setse 

 arising both on the surface and round the front and hind margins, many of them very 

 long and densely jjlumose ; the second joint short ; the thiixl fully as long as the first, 

 with the front margin nearly straight, the hinder convex, not decurrent, both densely 

 fringed with spines and long plumose setae ; the remaining joints similar to those of the 

 next pair, but shorter. 



Fourth Perseopods. — The side-plates with the lobe behind much deeper than the 

 front margin. The first joint somewhat longer and broader than in the preceding pair, 

 the hind margin sinuous, making the joint moi'e pear-shaped, the armature similar; the 

 third joint longer than the first, apparently more spiny on the hind, and less setose on 

 the front margin than in the third perseopods, but the difi"erence may be accidental, 

 since long plumose setae are easily broken off; the fourth joint about half the length of 

 the third, and much narrower, with small groups of spines at six points of the front 

 margin, and an apical group of setae behind ; the fifth joint longer than the fourth, but 

 narrower, with spines at seven points along the front margin, and setae at a dozen along 

 the sUghtly convex hind border ; the boat-shaped tapering finger as long as the fifth 

 joint ; the minute nail in one specimen was upturned, as represented in the figure 

 (PI. LXL), from which it may be presumed that these nails are movable, though they are 

 rarely seen except in line with the finger. 



Fifth Perseopods. — The side-plates broad and shallow, the hinder part a little deeper 

 than the front, fringed along much of the lower and all of the hinder margin. The first 

 joint broadly pear-shaped, much longer and wider than in the preceding peragopods, the 

 front margin much longer than the hinder, very convex above, much straighter below, 

 fringed with spinules, and on the lower part with small setae, the sinuous hind margin 

 closely set with setJB ; the second joint fringed on the straight front margin with setae ; 

 the third joint almost as long as the first, straight, parallel-sided, a very little decurrent 

 behind, with thirteen groups of spines along the front margin, and many interspersed 

 with setae along the hind margin, which, like the front, has a strong group of spines at 

 the apex ; the fourth joint almost as long as the third, straight, apically a little widened, 

 fringed in front with spines, behind with two principal groups, one apical, the other 

 distant about one-third of the length of the joint from the apex ; the fifth joint as long as 

 the third or nearly so, slender, straight, crowded with short spines in groups about the 

 front margin, several spines along the hind margin, and along the inner surface (not there- 

 fore shown in the figure), some thirteen groups of spines of various lengths, five or six being 



