SUPPLEMENT 191 



St. 1957: 3. ii. 37, off south side of Clarence island, 7 miles east of Cape Bowles, South Shetlands, large dredge, 

 heavy pattern, 4 ft. long (1-2 m.), 785-810 m. 



Serolis meridionalis Hodgson, i ? (breeding), i $ (non-breeding) incomplete. 



Serolis acuminata sp.n. (Text-figs. 23-26) 



Occurrence. St. 1660: 27. i. 36, 74° 46-4' S., 178° 23-4' E., 351 m., 8 ?? (breeding), 10 33, 2 VV (non-breeding) and 

 a number of immature specimens. 



One male and one female specimen from St. 1660 are chosen as holotypes. 



Description. The size of the largest male (Text-fig. 23) is 1 1 mm. in length and 10 mm. in greatest 

 breadth; the female, which is in the breeding condition, is 10 mm. in length and 8 mm. in greatest 

 breadth. The male is proportionately slightly broader than the female with a length: breadth ratio of 

 i-i:i as compared with the female ratio of 1-25:1. The head is twice as broad as long and broadest 

 anteriorly. The anterior margin shows two shallow excavations one on either side of a small pointed 

 rostrum ; behind the latter, running parallel with it, is a slight transverse ridge. A second ridge extends 

 between the anterior extremity of the eyes and the area of the head between the eyes is raised into two 

 rounded prominences; between these two, posteriorly, is a small median one. 



The suture line separating the head from the second thoracic (first pereion) somite extends to just 

 behind the eyes, which are about half the length of the head, reniform in shape and contain black 

 pigment. The lateral or coxal portion of the second thoracic somite on either side of the head is 

 marked by two low transverse ridges, one, extending outwards from just in front of the eye, curves 

 backwards to meet the second ridge which extends outwards from the middle region of the eye 

 (Text-fig. 23); the resulting single ridge curves slightly backwards and disappears. The median 

 portion of the somite, which is completely fused with the head, is narrow and bears a small back- 

 wardly projecting median spine. On either side of the junction of the tergal with the coxal region is 

 a low rounded eminence. The second, third and fourth pereion somites are subequal; each is produced 

 backwards in the mid-dorsal line into a small spiniform process, which increases in size from before 

 backwards. A low prominence occurs just within the lateral margins of all the pereion somites. The 

 sixth and seventh thoracic somites (fifth and sixth pereion) are slightly narrower than preceding 

 somites. Well-developed coxal plates are present on each of the second to the sixth pereion somites ; 

 those of the first three are separated by distinct sutures from their respective somites. The coxal 

 plates are not closely applied together and each is fringed with delicate hairs, which are longer on their 

 lateral than their posterior margins; the plates of the last two segments are longer than the preceding 

 ones, and those of the last extend backwards to beyond the tip of the uropods. The posterior margin 

 of each of the three free abdominal segments is produced into a median spiniform process similar to, 

 but slightly smaller than, those of the thoracic somites. The pleural plates of the third abdominal 

 segment extend backwards slightly farther than those of the second, but not quite as far as the level 

 of the base of the uropods. A short lateral carina is present on either side of the median one. 

 The terminal segment narrows considerably between the uropods and extends for some distance 

 beyond the tip of these, as a pointed process; the dorsal surface has a small low eminence in the 

 median line from which a median carina extends backwards disappearing at the level of the tip of 



the uropods. 



The antennule (Text-fig. 24 «) has a peduncle of four joints, the first one of which is broad and 

 geniculate, with a few scattered hairs; the second joint is about equal in length and breadth to the 

 first; the third is the same length as the second, but narrower and three times as long as the fourth. 

 The'flagellum consists of twelve joints and a minute terminal one; a single sensory seta is found at the 



distal end of all except the first three joints. 



7-2 



