292 DISCOVERY REPORTS 



respective coxal plates ; in S. paradoxa the position of the suture on the fifth free somite 

 is indicated by the presence of a slight groove. 



(4) In S. polaris the coxal plates of the seventh thoracic somite extend tv .he level of 

 the bases of the uropoda, whilst the pleural plates of the second abdom" lal segment 

 extend beyond them to the end of the terminal segment : the pleural plates of the third 

 segment are a little shorter than the coxal plates of the seventh thoracic somite. In 

 S. schythei the coxal plates of the seventh thoracic somite extend backwards for some 

 distance beyond the end of the terminal segment, whilst the pleural plates of the second 

 abdominal segment extend almost to the postero-lateral angle, and those of the third 

 to just beyond the anterior margin of the terminal segment. In S. paradoxa the coxal 

 plates of the seventh thoracic somite extend to about the middle of the terminal segment 

 and the pleural plates of both the second and third abdominal segments are short, only 

 just reaching beyond the anterior margin of the terminal segment. 



(5) The terminal segment of both S. schythei and S. polaris is more or less hexagonal 

 in outline, that of S. paradoxa is more triangular ; the spines on the transverse ridge, 

 which are present in the two former species, are much larger in S. polaris than in 

 S. schythei. The transverse ridge which is situated near the anterior margin in both 

 S. polaris and S. paradoxa is hardly seen in S. schythei. The large anterior median spine 

 is present in all three species. 



(6) The lamellar processes which occur on some of the joints of the flagellum of the 

 antenna in S. schythei are present, only less well developed, in S. polaris. Their place 

 is taken by strong spines in i?. paradoxa. 



(7) The modification of the form of the dactylus of the third appendage in the female 

 and immature male and of the fourth appendage in the mature male is seen in both 

 S. schythei and S. polaris. 



(8) The setae on the thoracic appendages of S. schythei are either simple, or serrated 

 or pectinate ; those of S. polaris are either simple or plumose, like those on the pleopods. 

 The setae on the thoracic appendages of S. paradoxa are like those of S. schythei, but 

 in this species the inner margin of the ischium, merus and carpus of the third appendage 

 of the adult male is fringed with delicate plumose setae. 



From the above comparison it is obvious that the three species are quite distinct. 



7. Serolis glacialis, Tattersall (Figs. 2 d, e, 4^). 



S.glacialis, Tattersall, 1921, p. 228, pi. vii, figs. 1-5; Monod, 1926, p. 35, figs. 33, 34. 



S. glacialis, Tattersall, var. austrogeorgiensis, Nordenstam, 1933, p. 65, pi. i, fig. i, text-fig. 16. 



Occurrence. St. 180: Palmer Archipelago, 160-330 m.; i $ (b.). 



St. 181 : Palmer Archipelago, 160-335 m.; 4,^^, 5 ?? (b.) 



St. 182: Palmer Archipelago, 278-500 m.; 2 ?? (b.), 6 immature specimens. 



St. 187: Palmer Archipelago, 259 m.; i ? (non-b.). 



Diagnostic characters. The body is broadly oval, slightly longer than broad, semi- 

 translucent, especially laterally. The head is nearly twice as wide as long with a small 

 rostral process between the bases of the antennules. Behind this process is a well- 

 marked transverse ridge which extends laterally to the sides of the cephalosome, and 



