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



setules ; the second, third, and fourth joints almost as in the first gnathopods, but the 

 distal margin of the third joint wider, and the hind margin of the wrist a little longer ; 

 the hand two and a half times as long as broad, the front margin nearly straight, with 

 one or two apical setules, the hind margin not much shorter than the front, carrying two 

 small setEe, apically produced into a small tooth bending a little outwards so as a little to 

 increase the width of the hand at this point ; within this tooth is planted a palmar spine, 

 with two larger spines of the same kind just beyond it, between which the tip of the 

 finger closes ; the palm-margin smooth, convex, scarcely oblique, fringed with setules ; 

 the finger smooth-edged. 



First Perseo20ods. — Side-plates oblong, more than twice as long as broad. Branchial 

 vesicles larger than the preceding pair, not so long as the first joint of the limb. 

 Marsupial plates similar to the preceding pair. First joint not reaching to the end of the 

 side-plate, fringed with setules ; second joint longer than broad ; third joint a little 

 longer than the fourth, subequal to the fifth, with setules at four points behind, and at 

 two in front, where it is slightly decurrent ; the straight fourth joint with setules at two 

 points of the hind margin ; the fifth joint slightly curved, armed at three points of the 

 hind margin ; the finger curved, more than half as long as the fifth joint, having part of 

 the inner margin pectinate. 



Second Perasopods. — Side-plates deep, but much broader than deep, reaching back 

 to the pleon-segments and completely covering the three following pairs of side-plates. 

 The branchial vesicles and marsupial plates similar to those of the preceding segment. 

 The first and second joints of the limb not reaching the lower rim of the side-plate ; the 

 third joint armed at five points, and the fourth at three points of the hind mai'gin ; the 

 limb otherwise similar to that of the first perseopods. 



TJiird Ferieopods. — Side-plates very small, not bilobed. Branchial vesicles and 

 marsupial plates very small, but deeper than the side-plates. First joint of the limb 

 long and narrow, the margins fringed with setules, the upper part a little wider than the 

 distal, and ciliated on the edges ; the second joint with setules at two points of the front 

 margin ; the third joint longer than the fourth, rather shorter than the fifth, armed at 

 three points in front and two behind, the fourth and fifth each at three points in front ; 

 the finger much curved, much more than half the length of the fifth joint, having part 

 of the inner margin pectinate. 



Fourth Ferieopods. — Side-plates a little less deep than in the preceding pair. 

 Branchial vesicles very small. The limbs very like the preceding perseopods, but with 

 the four terminal joints longer, the second armed only at one point, the third and fourth 

 at two points, of the front margin. 



Fifth Perasopods. — Side-plates small, broader than deep. The first joint not wider 

 above than below, shorter than in the two preceding pairs, the third joint also shorter, 

 so as to be subequal in length to the fourth ; the fifth joint rather longer than in the 

 preceding pair. 



