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



gaping widely, as they happened to be drawn apart in mounting for the microscope, 

 but it is of interest that in very few species could the inner plates have been thus 

 drawn apart either accidentally or on purpose without fracturing the maxillipeds. 



First Gnathopods. — Side-plates "wider below than above, with two or three 

 serrations at the hind corner of the convex lower margin. First joint reaching below 

 the side-plate, with a few long setae on the hind margin, and many spinules about 

 both margins ; second joint with a group of spines on the hinder apex, and spinules in 

 other parts ; third joint with groups of spines about the hind margin and near the 

 pointed apex ; the wrist not very much shorter than the first joint, considerably longer 

 than the hand, with five groups of setiform spines on the front margin, and many groups 

 of stronger spines along the hinder, and oblique part of the distal, margin ; the hand 

 parallel-sided, about three times as long as broad, armed like the wrist, with a group of 

 short thick spines near the angle of the palm, within which, and not beyond it, the 

 short finger closes over a convex palm set with setules. The numerous spines on the 

 hind margins of the hand and wrist are of various lengths, all apparently with small 

 accessory threads, and a great many, but not the longest, with broad bent tips and 

 extremely fine pectination of the edges for some distance below the tips ; the bent tip 

 when seen broadside instead of in profile appears to be a distal expansion, somewhat 

 paddle-shaped, with the convex edge presenting a slightly wrinkled look, and at the 

 lower part broken into teeth ; see the fig. gn.2.sp. 



Second Gnathopods. — The side-plates longer than the preceding pair and of more 

 even breadth. The branchial vesicles are shorter than the first joint of the limb, narrow 

 oval, with a long neck. Marsupial plates much longer than the first joint, and of 

 great breadth, with numerous setse of moderate length. The limb in general similar to 

 the first pair, but all the joints longer, the wrist with fewer spines, the hand equal in 

 length to the wrist, with nine pairs of the broad-ended spines along the hinder margin, 

 and five or six groups of spines on the inner surface adjoining. 



First Pergsopods. — Side-plates like the preceding pair, but larger. Branchial 

 vesicles broader, as long as the first joint. Marsupial plates of great size. First joint 

 reaching beyond the side-plate, with some spines on the hind margin, spinules on both 

 margins ; second joint with two groups on the hind margin ; third joint longer than 

 fourth, a little decurrent in front, ending obtusely, with slender spines at four points of 

 the hind margin, and stouter ones at four or five points of the front ; fourth joint with 

 spines at six points of the hind margin, a few spinules in front ; the fifth joint as long 

 as the third, parallel -sided, with numerous groups of short spines on the hind margin, 

 some setules on the front ; finger curved, with a small projecting point of the inner 

 margin adjoining the nail, and a small dorsal cilium near the base. 



Second Pcrseopods. — Side-plates broader and longer than the preceding pair, not 

 very deeply excavate behind. The branchial vesicles larger, a broader oval, the mar- 



