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



Second Gnathopods very similar in general character to the first. Side-plates rather 

 longer than those of the preceding segment, with three small spines on the margin just 

 above the cilium of the lower hinder angle. The branchial vesicles expanding at once 

 from the neck and continuing of nearly equal breadth to the lower, almost straight 

 margin. First, second, and thii-d joints as in the preceding pair, except that the first 

 and second are somewhat longer and narrower ; the wrist is here longer than the hand, 

 and the distal half wider, with some spines on the hind margin as well as at the apex ; 

 the hand oblong, front margin a Uttle convex, hind a little sinuous, with pectinate spines 

 on the lower part ; the palm sloping somewhat inwards, defined as in the previous pair, 

 not concave, but with an irregularly crenate margin, which the finger would apparently 

 a little overlap. 



First Perseopods. — Side-plates broad, most so at the centre, the front margin convex. 

 The first joint reaching beyond the side-plate, broadest distally, with setse on both 

 margins, of which the front is concave, the hinder convex ; third joint much longer than 

 the fourth, broad, very slightly decurrent, spines at six points on the hind margin, at 

 two in front ; fourth joint shorter and broader than fifth, with a few spines on the back 

 margin, and an apical tuft in front ; fifth joint tapering a little distally, slightly armed 

 on the straight hind margin, and having some spines at, and a little way above, the 

 apex in front ; finger short, the sharp nail forming a large part of its length. 



Second Perseopods. — Side-plates with length and breadth equal, very slightly 

 excavate behind. The joints of the limb similar to those of the preceding pair. 



Third Perieo2Jods. — Side-plates much wider than deep, the hind lobe descending 

 rather lower than the front, and carrying two or three spines. Branchial vesicles a long 

 oval, standing out from the narrow neck at the top. First joint a narrow oval, smaller 

 than the branchial vesicle, with spines on the lower half of the front margin, the hind 

 margin showing only two notches, not expanded below ; the four following joints with 

 spines on the front margin ; the third joint broader than the fourth, subequal in length, 

 with spines behind at two points ; fourth joint broader than fifth, slightly longer, with 

 spinules behind ; the fifth joint straight ; the finger small and slender, not nearly half as 

 long as the fifth joint, the nail short. 



Fourth Perseopods. — Side-plates similar to those of the preceding segment, but on a 

 smaller scale. Branchial vesicles similar in shape to those of the preceding segment, but 

 smaller, and, instead of descending, being directed abruptly forward, a fold starting 

 from the neck, as if to form a small accessory sac, reunites with the main vesicle. 

 First joint longer than in the preceding pair, front margin straighter, with more spines, 

 a seta near the base, hind margin notched at five points ; the rest of the limb similar to 

 the preceding, but all parts longer except the finger, and the third and fourth joints 

 decidedly longer than the fifth. 



Fifth Perseopods. — Side-plates not bilobed. Brancliial vesicles small, twisted upwards 



