EEPORT ON THE AMPHIPODA. 733 



curve of the preceding pair. The branchial vesicles, here and throughout, broad and 

 inflated ; this pair about as long as the first joint. The limb very similar to that of the 

 first gnathopods ; the first joint a little shorter, and at the top a little narrower ; the 

 third, fourth, and fifth joints rather longer, the fourth and fifth slightly narrower, 

 subequal to one another in length ; the armature similar. 



First Perieopocls. — Side-plates similar to the preceding pair, but rather longer and 

 broader, in each pair the front margin a little convex, and the hinder a little concave. 

 Limb as in the next pair. 



Second Perseopods. — Side-plates scarcely longer than the preceding pair, but below 

 the excavation equal in breadth to the two preceding pairs, the lower margin continuous 

 with theirs, the hind margin rounded below the excavation. The first joint about the 

 same size as that of the second gnathopod ; short feathered setse along the front margin, 

 numerous long ones on the lower part of both margins ; the short second joint having the 

 lower half of the hind margin and its apex crowded with them; the third joint nearly 

 as long as the first, with a group of long seta3 on the slightly decurrent apex of the 

 front margin, the hind margin straight, slightly serrate, fringed with numerous setse ; 

 the fourth joint subequal in length to the fifth, the apical group of the front margin 

 shorter than in the third joint, with a small group a little higher up, the hind margin 

 rather deeply serrate, fringed with long spines and seta3 of various lengths ; the fifth 

 joint narrow, slightly curved, with five groups of setae on the convex front margin, and 

 many groups of spines on the serrate hind margin ; the finger short and slender, scarcely 

 more than a third of the length of the fifth joint. In the Plate this and the succeeding 

 peraeopods are drawn on a larger scale than the two gnathopods ; to give warning of this, 

 as well as could conveniently be managed, on the Plate itself, I have added figures of 

 the natural size to show the comparative proportions of the second gnathopod and fifth 

 perseopod. 



Third Peraeopods. — The hind lobe of the side-plates deeper than the front one. The 

 limb is very similar to that of the two preceding pairs, the undilated first joint rather 

 longer, the third shorter, with both margins serrate and fringed with setae, some of 

 those on the front being so strong as rather to deserve the name of spines ; the fourth 

 joint has on the hind margin an apical group of spines and setae, and two groups of setae 

 higher up ; the fifth joint is longer than the fourth or third, and longer than the fifth 

 joint of the preceding pair. 



Fourth Perseopods. — The side-plates behind nearly as deep as the hind lobe in the 

 preceding segment. The first joint expanded, the margins nearly parallel, scarcely 

 serrate ; numerous very long setae arise on the inner surface along the hind margini 

 within the wing ; there is a fold of the integument on the outer surface at the upper part 

 near the front margin ; upon this margin there are various setae ; the remainder of the 

 limb resembles the corresponding part of the preceding pair, but with the third and fifth 



