196 THE VOYAGE OF H.M.S CHALLENGER. 



from ten to twelve peculiar slender spines, forming together a dense fascicle. In all 

 the legs the basal part is rather fully developed and muscular, and the exopod very power- 

 ful, with broad and lamellar basal section and eleven-articulated terminal jiart. 



The marsupial pouch in the female specimens (figs. 4, 5) was very large and ^jro- 

 truding, and filled with numerous ova or embryos. It is composed of three pairs of 

 incubatory lamellae, originating from the liases of the three posterior j^airs of legs. Of 

 these lamellae, the anterior pair are rather small, whereas the posterior are exceedingly 

 large and curved. 



The outer sexual appendages of the male (fig. 21) are slightly curved, and have at 

 the tip a transverse row of small sharply curved bristles. 



Of the caudal limbs in the female, only the first pair (see fig. 22) are developed in 

 the usual manner, having the form of narrow stems, somewhat geniculate in the middle, 

 and supplied with a few short bristles. On the four succeeding segments the limbs are 

 represented by broad, immobile plates, contiguous in the middl(\ and closely applied to 

 the ventral face, so as easily to be overlooked. These plates, which appear merely as 

 exjaansions of the sternal parts of the segments, have their edges somewhat angular, and 

 fringed with a few small bristles and short denticles. 



In the male, all of the caudal limbs are modified to powerful natatory organs, with 

 liroad and muscular basal parts and multiarticulate setiferous branches, the inner of which 

 exhibits at the base a remarkably broad and lamellar lateral expansion. In the first 

 pair (fig. 23) the terminal part of the inner branch is wholly wanting, but its lamellar 

 expansion still remains in its place. The fourth pair (fig. 24) are distinguished by the 

 outer branch being somewhat more produced than in the other pairs, and having the 

 outer articulations armed with short spines, instead of the usual natatory setae ; the 

 antepenultimate articulation of this branch is, moreover, produced on the outer side as an 

 acute-angled process (see fig. 25). 



The telson (fig. 26) is very large, fully as long as the two preceding segments taken 

 together, and exhibits an elongate, almost linear form, its length being about three times 

 as great as its breadth. The lateral edges are almost quite straight and parallel, and 

 armed with a great number of small denticles, more crowded in the outer part. The 

 apex is cleft in the middle by a rather narrow incision, occupying about one-fifth of the 

 length of the telson, and the terminal lobes are obtusely pointed and ]u-ovided at the tip 

 with a single denticle somewhat stronger than the lateral ones ; their inner edges are 

 throughout fringed with very fine spinules. 



The uropoda (fig. 27) are highly distinguished by the very slight development of the 

 marginal setae on the terminal plates, whereas both of the latter are partly spinous at 

 the edges. The inner plate is somewhat larger than the outer, and reaches the tip of the 

 telson ; it tapers regularly toward the apex, without exhibiting any conspicuous tume- 

 faction at the base, owing to the veiy slight development of the auditory apparatus ; its 



