1560 THE VOYAGE OF H.M.S. CHALLENGER. 



the outer plates not reaching far beyond the inner nor meeting over it, their outer 

 surface very convex, and broad except distally, carrying a few spinules. 



First Gnathopods. — Side-plates small, the lower front corner rounded and a little 

 produced forwards. The first joint for most of its length free from the side-plate, 

 rather broader above than below, the front margin bent out a little near the base, and 

 the hinder margin to a slight extent at some distance from the distal end ; the second 

 joint short, with some small spines at the apex of the convex hind margin, and on 

 the distal margin of the inner surface ; the third joint a little longer, distally widened 

 in front, the hind margin serrate, carrying some small spines ; the wrist wider than 

 the length of the hand, the front margin slightly convex, the hind margin somewhat 

 produced, in length nearly equalling the distal width of the joint, cut into minute teeth, 

 among which are three much more prominent than the rest, the apical being the 

 largest and in fact double though very slender ; much of the distal margin facing 

 the hind margin of the hand is also denticulate ; the hand is oval, the front margin 

 the more convex and scarcely serrate, the hind margin toothed like the wrist, with one 

 promineut double tooth not far from the narrow distal end, which is occupied by the 

 base of the very short, slightly curved, acute finger, the concave margin of which is 

 not quite smooth. A comparison of specimens shows that the denticulation of wrist 

 and hand in both pairs of gnathopods is subject to variation ; indeed, it is not absolutely 

 constant between the two limbs of a pair in one and the same specimen. 



Second Gnathopods. — Side-plates broader than the preceding pair. Branchial 

 vesicles longer than the first joint and much broader, with accessory lateral vesicles; the 

 marsupial plates much longer and broader than the branchial vesicles. The limb 

 similar to that of the first gnathopods, the first joint longer and rather broader, the 

 wrist a little longer but not broader. 



First Perseopods. — Side-plates wider than deep, the lower margin convex, 

 extending beyond the upper margin both before and behind. The branchial vesicles 

 and marsupial plates similar to those of the second gnathopods, but larger. The first 

 joint for most of its length free from the side-plate, the front margin slightly convex, 

 the hinder a little sinuous ; the second joint short, with some spinules on the hind 

 margin ; the third joint a little longer than the fourth, a little shorter than the fifth, 

 widened distally, with spinules on the front apex and along the hind margin ; the 

 fourth joint slightly narrowed distally, having spinules on the convex front and the 

 straight hind margin ; the fifth joint a little curved, tapering, the front margin 

 convex, the hinder slightly concave, with some spinules ; the finger minute, curved, 

 acute. 



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

 vesicles, marsupial plates, and joints of the limb scarcely differ from those of the first 

 perseopods, but the third and fourth joints are a little longer. 



