lO: 



transverse groove on each side of the terga, which in Xcphr. 'f/ioinsoni is described as deep, 

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

 and usually only consisting of a transverse row of shallow impressed 

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

 character Ncphr. Sibogae therefore apparently agrees with Xep/ir. Ckai/e7igeri, while it differs 

 from Av/Z/r. Thoinsoni by the deep sulcus wanting altogether. The abdominal terga 

 are finely punctate, though the puncta are of different size. The pleura of the 2"'' — s''' somites 

 also apparently resemble those of Xcphr. Challengeri\ when Fig. i of Plate XX\'I is indeed 

 accurate, the lower extremity of the pleura of the 2"'^ somite should, in Xcphr. Thomsoni, be 

 more elongate than in our new species, but this figure may perhajjs be inaccurate, for in Fi^"-. i 

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

 collected by the "Challenger" the 6'*^ somite carries a spinule in the middle of its posterior 

 margin, while the lateral ridge, 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 4'1' 

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

 fourth part and these t"<)ur spinules are about of the same size; a trace of a 5''', often wantin<T 

 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 fourtli, one observes, at 

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

 which is quadrate, just as wide as long, and the uropods resemble those of Xcphr. Challengeri, 

 but the submedian elevated parts of the upjjer 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 tlagcllum measurin^^ 

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

 {^^ miu.), i.e. about one-third the whole length. The i^' 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 Spenck B.vte, it should in Xcphr. Thoni- 

 soni be here convex; the sjjinule at the inner distal angle is very small. The 3'''i joint is but 

 little shorter than the 2"'' and, like in Xcphr. Thomsoni, the outer flagellum appears distinctly 

 more robust than the inn<-r. 



The external antennae, measured also from the frontal margin, are ;20 mm. lone, the 

 jjeduncle 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-timcs as long as the internal antennae. 

 They clo.sely resemble those of Xcphr. Thomsotii. 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"'' joint: the scaphocerite (Pig. 1 8<^) that just reaches the distal margin of the 4"' or penultimate 

 joint of the peduncle, presents the same form as in Xcphr. Thoiiisoni, 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 broatl, in the largest male it is 12 mm. lung and 1 1 nun. 



SlItOGA-FXI'KlJlTlK XXXIXa-. I4 



