1584 THE VOYAGE OF H.M.S. CHALLENGER. 



Atlantic specimen, though far less strongly ; the smoothness of the margin in question 

 is probably a juvenile character. 



First and Second Perseopods similar to those of the female already described. The 

 branchial vesicles of these and the two following pairs having short transverse pockets or 

 folds. 



Third Perseopods differing from those of the previous description chiefly in the first 

 joint which is elongate oval, more convex at the finely serrate hind margin than at the 

 front, which is armed with two or three spinules in the upper part, and serrate at six 

 points in the lower, the breadth being about the same at the proximal and distal ends. 



Fourth Perseopods differing from those of the Atlantic form in the first joint, which is 

 rather pear-shaped than circular, a little shorter than the first joint of the third perseopods, 

 much broader above, but at the distal end a little narrower, both margins strongly convex 

 at the upper part, especially the hind margin, the front margin in the lower half tending 

 rather to concave, serrate at six or seven points. 



Fifth Perseopods. — The pear-shaped first joint shorter as well as much narrower than 

 that of the fourth perasopods, less strikingly narrowed before reaching the distal end than 

 in the Atlantic specimen. The remaining joints feeble, together much shorter than the 

 first ; the third not greatly longer than the fifth, the fifth a little longer than the fourth ; 

 the nafl very small, spine-like. In the female specimen these limbs are very nearly as in 

 the Atlantic specimen, but the first joint has not the narrowed distal part so much 

 prolonged. 



Pleopods similar to those already described. 



Uropods similar to those of the Atlantic form, but with the inner ramus of the first 

 pair reaching just beyond the telson, the inner apex of the third pair being almost or 

 quite level with the apex of the telson. 



Telson shorter than the double segment, with which it is coalesced, not nearly twice 

 as long as broad ; the lateral margin smooth or nearly so above, strongly pectinate 

 below ; the apex acute. In the female specimen more elongate, yet not quite so long as 

 the preceding segment. 



Length. — The female specimen from which the full figure was taken, measured, in 

 the position figured, in a straight line from the apex of the rostrum to the distal end 

 of the first uropods, almost three-quarters of an inch, the full length when extended 

 being rather over an inch. The male specimen from which the details were drawn was a 

 good deal smaller, measuring about half an inch in a slightly bent position. 



Locality. — July 1875, North Pacific, between Japan and Honolulu; surface. Four 

 specimens. 



Remarks. — It will be noticed, as an example of the correlation of parts, that the short 

 telson in the specimen here described goes with a short rostrum, as in the Atlantic 



