356 DISCOVERY REPORTS 



the sixth and seventh thoracic somites is complete, only the posterior suture of the 

 seventh segment being obsolete for a short distance in the mid-dorsal region ; in this 

 species therefore the sixth thoracic somite is free, and the seventh is fused for a short 

 space with the first abdominal segment. 



(2) The body of S. pagenstecheri is slightly broader in proportion to its length than 

 that of S. aspera. 



(3) The body of S. pagenstecheri is covered with scattered hairs, which are most 

 numerous along the posterior margins of the somites ; in S. aspera they are very sparse 

 and are not concentrated along the margins of the somites, but are moderately abundant 

 along the posterior free margins of the coxal and pleural plates. 



(4) The terminal segment of both species is broader than long, but that of S. aspera 

 narrows more rapidly behind the articulation of the uropods ; the posterior extremity is 

 definitely trifid in S. aspera, in most specimens of S. pagenstecheri it is truncate or only 

 slightly trifid. 



(5) In both species the terminal segment bears on its dorsal surface a strong median 

 spine in an anterior position, which is followed by a low median carina extending to the 

 posterior extremity of the segment ; on either side of this are two lateral carinae ending 

 in spiniform processes at some distance from the lateral margins. In S. aspera the 

 carinae next to the median are smaller than the outer, whereas in S. pagenstecheri they 

 are all of approximately equal size. 



(6) The third joint of the palp of the maxilliped of S. pagenstecheri bears at its outer 

 distal angle a minute extra joint which does not extend beyond the end of the third, 

 and bears a group of long setae. This joint is absent from the maxilliped of S. aspera. 



(7) The thoracic appendages are very much alike in both species ; the modified spines 

 on the propodus of both the second and third appendages of the male are similar, and 

 the inner borders of the carpus, merus and ischium are fringed with a dense mass of 

 fine hairs in both species. Similar hairs are present on the propodus, carpus, merus and 

 ischium of the last appendage of the mature male of S. pagenstecheri, but these are 

 absent from the corresponding appendage in S. aspera. 



The distribution of the two species is the same : all recorded specimens have been 

 collected near South Georgia. 



33. Serolis australiensis, Beddard. 



S. australiensis, Beddard, 1884 ^>, p.6g, pl.vi, figs. 3-6; Whitelegge, i90i,p.237; Chilton, 1917, pp.396, 

 400, fig. 10; Nordenstam, 1933, pp. 90-2. 



Diagnostic characters. The largest specimen of this species so far collected is a 

 female 14 mm. in length by 11 mm. in breadth, whilst the largest male measures lomm. 

 in length and 9 mm. in breadth: as in many Serolids, the males appear to be pro- 

 portionately broader than the females. 



The form of the body is oval; its most characteristic feature is the presence of a large 

 number of tubercles, which are scattered over its surface and are especially large on the 

 posterior borders of the somites and on the dorsal surface of the terminal segment. 



