IO = 



transverse groove on each side of the terga, which in Nephr. Thomsoni is described as deep, 

 in Nephr. Sibogae is only represented by a narrow impressed line, quite shallow 

 and u s u a 1 1 y only consisting of a transverse row of shallow impressed 

 puncta: on the 5 ,h tergum this transverse row of puncta is even very inconspicuous. In this 

 character Nephr. Sibogae therefore apparently agrees with Nephr. Challengeri, while it differs 

 from Nephr. Thomsoni by the deep sulcus want ing altogether. The abdominal terga 

 are finely punctate, though the puncta are of different size. The pleura of the 2 nd — 5 th somites 

 also apparently resemble those of Nephr. Challengeri; when Fig. i of Plate XXVI is indeed 

 accurate, the lower extremity of the pleura of the 2 nd somite should, in Nephr. Thomsoni, be 

 more elongate than in our new species, but this figure may perhaps be inaccurate, for in Fig. i 

 of Plate XXV the pleura show the same form as in Nephr. Sibogae. Like in the two species 

 collected by the "Challenger" the 6 th somite carries a spinule in the middle of its posterior 

 margin, while the lateral riclge, that separates the tergum from the pleura, appears finely 

 denticulate on its anterior half externally and armed with a small spine near the centre. A 4 ,h 

 spinule, not found in the two other species, occurs in the midline of the somite near the anterior 

 fourth part and these four spinules are about of the same size; a tracé of a 5 th , often wanting 

 at all, is observed also in the midline just in front of the spinule on the posterior margin and, 

 midway between this spinule and that which is situated at the anterior fourth, one observes, at 

 either side of the midline and close to it, also the tracé of a rudimentary spinule. The telson 

 which is quadrate, just as wide as long, and the uropods resemble those of Nephr. Cha/Iengeri, 

 but the submedian elevated parts of the upper surface of the telson bear often 3 or 4 small 

 spinules of unequal size, posterior to the anterior pair of spines. 



In the largest specimen, the male long 184 mm., the internal antennae, measured from 

 the frontal margin of the carapace, prove to be 105 mm. long, the inner flagellum measuring 

 78 mm., the other 56 mm.; they are almost twice as long as the carapace without the rostrum 

 (55 mm.), i. e. about one-third the whole length. The i st joint of the peduncle, that measures 

 12 mm. and that is about twice as long as the two following joints taken together (7 mm.), 

 appears rather flattened beneath, while, according to Spence Bate, it should in Nephr. Thom- 

 soni be here convex; the spinule at the inner distal angle is very small. The 3 rd joint is but 

 little shorter than the 2 nd and, like in Nephr. Thomsoni, the outer flagellum appears distinctly 

 more robust than the inner. 



The external antennae, measured also from the frontal margin, are 320 mm. long, the 

 peduncle 30 mm., so that they prove to be one and three- fourth times as long as the body, 

 6-times as long as the carapace without the rostrum and 3-times as long as the internal- antennae. 

 They closely resemble those of Nephr. Thomsoni. The peduncle is a little shorter than the 

 rostrum and bears a sharp spine at the distal extremity of the curved outer margin of the 

 2 nd joint; the scaphocerite (Fig. 18^) that just reaches the distal margin of the 4 th or penultimate 

 joint of the peduncle, presents the same form as in Nephr. Thomsoni, but the slightly arcuate, 

 outer margin is unarmed at the distal extremity and does here not terminate in a tooth or 

 spine; the upper surface presents a slight pubescence and the antero-internal margin is rounded. 

 The scaphocerite is hardly longer than broad, in the largest male it is 12 mm. long and 11 mm. 



SIBOGA-F.XrEDITIE XXXIX a-. 14 



