1494 THE VOYAGE OF H.M.S. CHALLENGER. 



Fourth Perseopods. — The first joint much longer than in the preceding pair, having 

 in the broad upper part a small semicircular slit on the outer surface, followed by a 

 longitudinal groove on the inner surface reaching far down into the narrowed lower part; 

 the front margin presents a considerable concavity to fit the hind margin of the first 

 joint of the preceding pair, and its rounded apex is produced below that of the hind 

 margin ; the upper part of the hind margin is strongly convex, the lower nearly straight ; 

 the small second joint is fixed so high up within the hind margin of the first joint, 

 that the finger cannot reach the apex of that joint ; the third joint considerably longer 

 than the fourth, the hinder apex rounded, very slightly produced, the front margin not 

 produced, pectinate with teeth directed a little backwards, increasing in strength as they 

 aj)proach the apex ; the fourth joint stouter and a little longer than the fifth, its front 

 margin armed much like that of the third ; the fifth joint straight, narrowing distally, 

 with very fine pectination of the front margin ; the finger small, acute, about a third 

 the length of the fifth joint. 



Fifth Perseopods. — Side-plates triangular, with straight hind margin, and slightly 

 rounded apex ; they are coalesced with the segment, except for a small space behind. 

 The first joint much longer than broad, with the hind margin convex till very near 

 the narrow apex, the front margin concave for most of its length ; the second joint 

 not longer than broad, with very convex front margin ; the third two or three times 

 as long as the second, not broader, strongly bent upwards, with convex front margin and 

 smoothly rounded apex. In the absence of any other joints beyond the third on this 

 limb, the present species differs strongly from " Tanyscelus sphseroma," Claus. 



Pleopods. — Coupling spines minute ; cleft spine with a narrow subapical dilatation 

 to the longer arm ; joints of the rami seven to eight in number. 



Uropods. — Peduncles of the first pair bending inwards, shorter than the rami, the 

 convex outer margin finely pectinate ; the outer ramus shorter and narrower than the 

 inner, with finely pectinate outer margin ; the broad inner ramus does not quite reach 

 the end of the telson, narrowing rather suddenly to its sharp apex, with the inner margin 

 divided into about eight little teeth and like the outer finely pectinate ; the peduncles 

 and rami of the second pair much shorter than those of the first, the rami narrow, the 

 outer much smaller than the inner, the inner margin finely pectinate, and the outer also 

 at the lower part ; the peduncles of the third pair widening distally, a little longer than 

 the distal breadth, rather longer than the outer, a little shorter than the inner, ramus ; 

 the little outer ramus not half the length nor nearly half the breadth of the inner ramus, 

 the inner margin in each finely pectinate, the inner ramus reaching a little beyond the 

 telson. 



Telson distally broadly rounded, not so long as the breadth at the base of the 

 third uropods, where it is completely coalesced with the broad preceding composite 

 segment, its position marked by the gently converging sides of the segment being here 



