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



densely crowded together, and arranged most regularly side by side in a row, forming a 

 double spii-al along the membranous lamella, doubled over the concavity of the epipodite- 

 plate, so as anteriorly almost completely to fill up the concavity. As in the female, 

 they increase in size from behind forwards, but much more gradually (see fig. 6). 



Of the legs, all but the last pair are provided with strongly developed natatory exopo- 

 dites, the basal part of which (see figs. 8-11) is remarkably broad and lamellar. In regard 

 also to the structure of the endopodal part of the legs some differences from that in the 

 female may be found. Thus, in the two anterior pairs (figs. 8, 9) the basal joint is compara- 

 tively larger and more dilated in the proximal part, to receive the strong muscles moving 

 the exopodite. In the second pair (fig. 9) this joint is twisted in a peculiar manner, the 

 rido-e running along the lower side being more elevated and strongly flexuous. More- 

 over, the penultimate joint of this pair of legs is markedly distinguished by its inner 

 edo-e beino- strondv denticulate or exhibiting a serrate crest, a condition quite absent 

 in the female. In the third and fourth pairs of legs (figs. 10, 11) the basal joint 

 exhibits a form quite dissimilar to that in the female, not being simple and cylindrical, 

 but considerably dilated in the proximal part, and at the base of the exopodite provided 

 with a number of very strong hairy setas. The last pair of legs (fig. 1 2) nearly agree 

 in the form and relation of the joints with those in the female, but are distinguished 

 by two unusually strong and densely hairy setse, arising from the outer edge of the 

 basal joint. 



There are two pairs of well-developed pleopoda affixed to the two anterior caudal 

 segments (see PI. VI. fig. 3). They consist (PI. VIII. figs. 13, 14) each of a narrow 

 basal part divided into two unequal segments, and of two very short branches provided 

 with long natatory setse. Of these branches (fig. 13, a) the outer one is distinctly 

 biarticulate, and bears at the tip four setre, whereas the inner is uniarticulate and 

 provided with six setse, two of which are aflixed to the inner edge; moreover, this 

 branch exhibits at the outer edge, close to the apex, a small projection bearing two 

 minute auditory bristles. Both pairs of pleopoda are essentially of the same structure, 

 with this diflerence, however, that the basal part of the first pair (fig. 13) is more richly 

 supplied with bristles. At each side of the pleopoda there are on the two anterior 

 segments a number of strong ciliated setse (see figs. 13, 14), and on the ventral surface 

 of the two succeeding segments four strong seta3 likewise occur (see PI. VI. fig. 3), as it 

 were, in place of pleopoda.. 



The telson (see PI. VIII. fig. 15) is considerably more elongate than in the female, 

 and, moreover, readily distinguished by the strong geniculate fiexure occurring anterior 

 to the middle (see also PI. VI. fig. 3), whereby the basal part appears sharply marked 

 off" from the terminal part. The latter is armed on each side with about fifteen ciliated 

 denticles, whereas in the female, as above stated, the number of denticles is only nine 

 on each side. 



