1304 THE VOYAGE OF H.M.S. CHALLENGER. 



Maxillipeds. — The inner plate short, strongly projecting, cleft far down the middle, 

 the distal margin of each half convex, set with many spinules ; outer plates to a certain 

 extent " prismatic," each having two inner margins, one of which carries several long 

 and short spines ; the outer margin is convex, smooth, the apical carries three or four 

 unequal spines in notches ; the outer surface of the plates is armed with many unequal 

 spines, nineteen or twenty being counted on one plate and thirteen on the other ; the 

 basal joint carrying these plates has several spines on each lateral margin, and at the 

 centre of the distal margin a small lobe or plate apically surmounted by two spines. 



First Gnathopods. — Side-plates shallow, the lower margin nearly straight. The 

 first joint nearly equal in length to the following four together, the inner front margin 

 fringed with setiform spines, the hinder margin with spines of various lengths ; the 

 second joint short, with some spines on the hind margin ; the third joint with the front 

 margin on the inner surface longer than that on the outer, the hind margin with 

 several slender spines ; the wrist widening distally, much longer and broader than the 

 hand, the front margin much longer than the hind one, each with spines or spinules at 

 intervals, the sinuous distal margin with many spines, especially on the inner surface ; 

 the hand almost triangular, broadest at the base, not twice as long as broad, with five 

 or six spines on each serrate margin and four on the inner surface, the narrow apex 

 truncate ; the finger very narrow, straight, when complete about half the length of the 

 hand. 



Second Gnathopods. — The side-plates shallow, broader than the first pair, the lower 

 margin very sinuous. Branchial vesicles elongate, oval, narrower than the first joint and 

 much shorter. Marsupial plates in an early stage of development, smooth-edged, as wide 

 as the branchial vesicles and rather more than half their length. The first joint as long 

 as the wrist, hand, and finger together, fringed with spines on both margins ; the second 

 and third joints nearly.as in the first gnathopods, but the second rather longer ; the wrist 

 much longer and much narrower than in the first pair, similarly armed, distally widened, 

 but not greatly ; the hand shorter and narrower than the wrist, longer but narrower than 

 the hand of the first gnathopod, with seven small spines on the hind margin and three 

 or four on the front. 



First Pereeoptods. — Side-plates broad, shallow, especially in front, the lower margin 

 sinuous. Branchial vesicles much larger than the preceding pair, as long as the first joint 

 and broader. The marsupial plates much narrower than the branchial vesicles and less 

 than half their length. The first joint nearly as in the second gnathopods, but rather 

 broader; the second joint rather longer than broad; the third joint shorter and much 

 narrower than the first, considerably longer than the fourth or fifth ; the fourth joint 

 rather shorter but brc-iider than the fifth ; the fifth joint narrowing to the apex, slightly 

 curved, having like the two preceding joints several small spines on the hind margin ; 

 the third has also several spines on the front margin, and the fourth has two or three ; 



