1436 THE VOYAGE OF H.M.S. CHALLENGER. 



from the hind margin. The first joint is longer and broader than that of the first 

 gnathopods, by which it is overlapped above ; the front margin convex, the hinder 

 sinuous, the interior of the joint containing a long oval pocket of gland-cells ; the 

 second, third, and fourth joints similar to those of the preceding pair, but thinner ; 

 the hand much longer, thinner at the base, from which it tapers to nearly the middle, 

 in a somewhat oval form, fringed with spinules or setules, the remainder being drawn 

 out into a long, slender, nearly straight process, with parallel sides, the minute finger 

 being socketed in the apex as in the preceding pair, minutely scabrous on its inner 

 surface. 



First Peneopods. — Side-plates distinct, much, broader than deep, shallow, axe-like, 

 but with the ends rounded. The branchial vesicles sack-like, much longer than the first 

 joint, with some nine subsidiary pockets. The limb much longer than the gnathopods ; 

 the first joint with a bent neck, the distal half wider than the proximal ; the second 

 joint considerably longer than broad, channelled in front ; the third not quite so long- 

 as the second, widening at once from the narrow neck, so that without the neck the 

 width is fully as great as the length, the hind margin finely pectinate ; the fourth joint 

 not so long as the first joint, but broader, with scabrous surface ; the front margin 

 smooth, gently convex ; the hind margin forming with the emarginate distal border 

 (where the joint is widest) a triangular process, both these margins being pectinate, 

 and the hind margin having also a small tooth or projection at two or three points, 

 attended by spinules, of which there are several submarginal on the lower part of the 

 joint ; the fifth joint a little shorter than the fourth, much thinner, folding across the 

 distal margin of the fourth joint as though it were a finger to it, and in this position 

 extending much beyond it ; the hinder margin pectinate, the front gently convex, furred, 

 the fur extending over much of the surface ; the finger slender, slightly curved, more 

 than half the length of the fifth joint, pectinate for two-thirds of the hiud margin. 



Second Perieopods differing very slightly from the first, except that the fourth joint 

 is rather narrower at the base, has a more regular hind margin, and distally forms a 

 triangular process which is considerably longer than that in the preceding pair, so that 

 the fifth joint, although rather longer than in the first perseopods, does not extend so 

 much beyond the fourth joint as in that pair. In both pairs the expanded fourth joint 

 contains gland-cells. 



Third Perseopods massive. The side-plates larger than in the preceding pairs, if not 

 in proportion to the increased size of the joint ; the process on the inner surface is 

 broad, with sinuous lower margin. The first joint of great breadth ; the front margin 

 formed by an oblique line descending to the point of greatest breadth, and below this by 

 a strongly sinuous bne, at first concave and then convex ; the hind margin has an upper 

 rounded lobe and is then gently sinuous ; there is a ridge down the centre of the inner 

 urface, with a small lobe at each extremity ; the second joint a little longer than broad, 



