j6o discovery reports 



Distribution. The Discovery specimens are all recorded from an area between 47° S., 60" W. and 

 51° S., 66° 45' W., at depths ranging from 219 to 100 m. Ohlin's specimen came from 38° S., 56° W. 

 at a depth of 52 fathoms (approximately 93-6 m.). Thus the localities from which this species has 

 been collected are all close together and all of them are outside the Antarctic Convergence. 



Edotia oculopetiolata sp.n. (Text-fig. ga-g) 



Edotia tuberculata Guerin-Meneville, Nordenstam, 1933, pp. 95-7, figs. 22-23 a. 



Occurrence. St. 123: 15. xii. 26, off mouth of Cumberland Bay, South Georgia, 230-250 m., i ?; 230 m., 2 im- 

 mature specimens; 220 m., i immature specimen. St. 140: 23. xii. 26, Stromness Harbour, South Georgia, 122- 

 136 m., I ?. St. 144: 5. i. 27, off mouth of Stromness Harbour, South Georgia, 155-178 m., 3 ?? (breeding), 4 ^3. 

 St. 180: ii.iii. 27, Schollaert Channel, Palmer Archipelago, 160-33001., i <?. St. 161: 12. iii. 27, SchoUaert 

 Channel, Palmer Archipelago, 64° 20' 00" S., 63° 01' 00" W., 335 m., i c? (damaged). St. 195: 30. iii. 27, Admiralty 

 Bay, King George Island, South Shetlands, 391 m., i (J and i ?. St. WS 25: 17. xii. 26, Undine Harbour (North), 

 South Georgia, 18-27 ^■' i cJ- St. MS 71: 9. iii. 26, East Cumberland Bay, South Georgia, 110-60 m., i ?. 



The holotypes are from St. 195. 



Remarks. Nordenstam (1933, p. 95) identified some specimens from the Swedish Antarctic 

 Expedition as E. tuberculata, but he was incorrect in his diagnosis. His specimens differed from 

 Guerin-Meneville's description of the type in a number of characters, and I consider that they should 

 be included in a new species, E. oculopetiolata. 



Perhaps the most obvious difference between the two forms is that of size. Ohlin (1901, p. 292) 

 gives the length of E. tuberculata as 29 mm. and breadth as 11 mm.; Miers (1881, p. 73) gives the 

 length as 30 mm. and breadth also as 1 1 mm. Nordenstam's specimens, on the other hand, were 

 considerably smaller, a mature male measuring 10 mm. in length and a mature female 9-10 mm. 

 The specimens of the Discovery collections are approximately the same size as those of Nordenstam; 

 the largest male is 1 1 mm. in length and 4 mm. in greatest breadth. The true E. tuberculata is therefore 

 about three times as large as E. oculopetiolata. 



Apart from size, there are other important differences between the two species. Nordenstam 

 himself (p. 96) noticed that in his specimens 'the eyes are placed on large tubercles, lateral margins of 

 the head are somewhat concave, and dorsal side of head has four tubercles '. The tubercles bearing 

 the eyes (Text-fig. 9/) are so obvious that, if present, they cannot be overlooked, yet none of the 

 descriptions of E. tuberculata contains any mention of such a feature ; for this reason Nordenstam's 

 identification seems open to doubt. 



An examination of the British Museum specimens of E. tuberculata has finally settled the point, for 

 in these the eyes are small, lateral in position, and not on tubercles. The apical segment of the uropod 

 in E. tuberculata (Miers, 1881, pi. iii, 6) is longer and very much more acute than that of Nordenstam's 

 species (1933, p. 97, fig. 23a). In the introduction to the genus, reference has already been made to 

 the form of coxae and the modification of the brood pouch in this species (p. 155). 



These structural differences are further supported by differences in distribution. The true E. tuber- 

 culata is found in waters around the south of South America and the shores of the Falkland Islands, 

 that is, in areas outside the Antarctic Convergence; on the other hand, Nordenstam's E. tuberculata 

 and the corresponding specimens in the Discovery collections occur in shallow waters off South 

 Georgia, the South Shetland Islands and the Palmer Archipelago — all within the Convergence. 



Evidence is accumulating to show that shallow-water species of both isopods and amphipods occur 

 in localities either outside, or inside, the Antarctic Convergence, but that any one species does not 

 occur in both areas. If Nordenstam's identification were correct, then E. tuberculata would be an 

 exception to this rule. 



