OP THE ' SOUTHERN CROSS ' EXPEDITION. 45 



margins, as loug as the Sth and twice as long as the 4th joint, 

 the 2nd, 3rd, and 4th joints setose, the 5th spinous on the hind 

 margins. The iast three pairs increasing slightly in lengfli 

 successively, similar in form ; the 1st joint much expanded, the 

 upper margin straight, the hind margin slightly serrate in the 

 middle ; remaining joints spinous. The side-plate of the 3rd j)air 

 about as wide as deep. 



Uropods extending equally behind ; peduncles of the 1st pair 

 twice as long as the equal rami; those of the 2nd pair about 

 one-tburth longer than the subequal rami ; third pair lanceolate, 

 peduncles two-thirds the length of the rami; outer ramus one- 

 fourth longer than inner, both spinous on the outer, setose on 

 the inner margin. 



Telson reaching considerably beyond the eud of the peduncle 

 of the third uropods, widely cleft for three-fourths of its 

 length, with submarginal spines along the outer and inner 

 margius, and two spines at the tip of each division. 



Length 16 mm. 



O. Eossi *, n. sp. (PI. 7. figs. 18-23.) 



Lat. 78° 35' S. ; Eeb. 18, 1900 ; near surface. Many specimens. 



Body slightly compressed. First 4 side-jplates about as deep 

 as the segments, the 1st expanded in front, the rest very slightly 

 expanded below, subrectangular. Second segment of the meso- 

 some shorter than the rest, which are subequal. Third segment 

 of the metasome with the hind margin almost straight, smooth, 

 posterior angle sulacute, lower margin convex. Pirst segment 

 of the urosome with a dorsal depression. 



Head as loug as the 2nd segment ; lateral angle rounded. 

 Eyes large, black, long-oval, expanded below. 



Upper antennae little longer than the head : 1st joint almost 

 as broad as long, 2nd very short, 3rd rather longer than the 2nd. 

 Magellum 18-jointed; 1st joint as long as the next five, with the 

 usual long setae and rov/s of setules ; accessory appendage 

 6-jointed, the 1st as long as the next four. 



Lower antennae : first and third joints subequal, the 2nd rather 

 longer. 



First guathopods : first joint strong, rather longer than the 

 next three. Carpus short and produced behind beyond the base 

 of the propodos, setose ; propodos truncate, contracted below 



* After the well-koowii Antarctic navigator. 



