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



very slender form. Tliey are nearly of the same thit-kness throughout, and rather 

 abundantly furiiislied with 1)ristles. The terminal joint has not the appearance of a claw, 

 hut is linear in shape, and very densely setigerous, more especially at the inner edge, the 

 apex being obtusely rounded. 



The gills (see PL X. fig. 2) occur at the bases of all the legs, except the last, and 

 present alike in their arrangement and structural details a great resemblance to the 

 same organs in Gnathoj^hausia. They are divided into three principal l)ranches, 

 the largest bent in towards the ventral face (see PI. IX. fig. 14), whereas the two others 

 are wholly covered by the lateral parts of the carapace. Every branch is more or less 

 distinctly bipinnate, and the pinnulae are divided into numerous rather irregularly 

 disposed, lobular projections (see PI. X. fig. .3). In the interior of the lobules small 

 opaque granular bodies are scattered, apparently blood-cells, similar to those observed 

 \\ithin the several oral parts, and also to some extent mthin the legs. In the male, the 

 gills (see PL X. figs. 14, 16) are, on the whole, precisely similar to those in the female, 

 excepting that the inner branch (fig. 15) is somewhat larger and more decidedly 

 arborescent, the pinnulse being in part subdivided. 



The marsupial pouch in one of the specimens obtained (PL IX. fig. l) is very large, 

 and projects considerably beneath the trunk. As in the Lophogastridse, it is composed of 

 seven pairs of large ovato-lanceolate lamellge, setigerous at their edges (fig. 15), and 

 each overlapping the other in the median line. 



The caudal limbs (PL X. fig. 8), as in the Lophogastridse, are developed in both sexes 

 into powerful natatory organs, the terminal branches very slender and subdivided into 

 numerous short setigerous joints. In the male these limbs (fig. 17) are somewhat more 

 strongly developed than in the female, the basal part being rather more dilated, and 

 exteriorly jutting out into a rounded lobe. In lx)th sexes the inner branch is a trifle 

 shorter than the outer. 



The telson (see PL X. fig. 9) is rather elongate and slender, gradually tapering in its 

 outer part toward the apex, which is narrowly truncate. The lateral edges of the telson 

 are in the distal part armed with a row of rather strong Ijut somewhat unequal spinules, 

 and two simdar Ijut considerably longer ones occur on the apex, in addition to two small 

 l)ristles in the middle. 



The uropoda [ibid.) somewhat exceed the telson in length, and have the inner plate 

 lanceolate, the outer rather broader and obliquely truncate at the apex, or j)rojectiug as a 

 short terminal lolie, marked off from the plate Ijy a distinctly defined transverse suture. 

 The outer edge of this plate is perfectly straight and bare, terminating in an obtuse 

 angle, from which issue three short denticles (see fig. 11). 



The caudal fan of the male agrees precisely in aU its details with that of the female. 



Nervous System. — In extracting the ventral cord from the specimen selected for 

 anatomical examination, I failed to discover more than seven ganglia belonging to the 



