HEMIASTERIDAE 225 



St. 39. 25. iii. 26. East Cumberland Bay, South Georgia, 179-235 m. Several specimens. 



St. 42. I. iv. 26. Off Cumberland Bay, South Georgia, 120-204 m. 5 specimens. 



St. 45. 6. iv. 26. East of Jason Island, South Georgia, 238-270 m. 8 specimens. 



St. 140. 23. xii. 26. Stromness Harbour to Larsen Point, South Georgia, 122-136 m. 8 young 

 specimens. 



St. 142. 30. xii. 26. East Cumberland Bay, South Georgia, 88-273 m. Several specimens. 



St. 146. 8. i. 27. 53° 48' S, 36° 02' W, South Georgia, 728 m. i young specimen(?). 



St. 148. 9. i. 27. Off Cape Saunders, South Georgia, 132-148 m. 2 very young specimens. 



St. 167. 20. ii. 27. Off Signy Island, South Orkney Islands, 244-344 m. i medium-sized, i large, 

 9 small specimens. 



St. 182. 14. iii. 27. Schollaert Channel, Palmer Archipelago, 278-500 m. 2 very young speci- 

 mens. 



St. WS32. 21. xii. 26. Mouth of Drygalski Fjord, South Georgia, 91-225 m. i specimen. 



St. WS 62. 19. i. 27. Wilson Harbour, South Georgia, 26-83 m. Several specimens. 



St. MS 15. 17. ii. 25. East Cumberland Bay, South Georgia, 109 m. 9 specimens. 



St. MS 68. 2. iii. 26. East Cumberland Bay, South Georgia, 220-247 m. Several specimens. 



St. MS 69. 5. iii. 26. East Cumberland Bay, South Georgia, 146 m. i specimen. 



Attention should be called to the rather extraordinary variation which occurs in this 

 species (as in Amphipneiistes Lorioli) in regard to the size of the marsupia ; they may, 

 indeed, be twice as large in one specimen as in another. Also in the males the depth of 

 the petals varies very considerably, and they are sometimes so deep that one would 

 rather think them to be female marsupia. The small size of the genital pores shows, 

 however, that they are actually males (as I have also verified by an examination of the 

 gonads). 



The extraordinary development of the marsupia in the female is best realized by in- 

 spection of the interior side of the test. Plate III, figs. 11,12 represent the inside of the 

 test of a female and a male. 



The commensal bivalve Mollusc occurring on this species has been described by 

 Grieg (Echinoderms from the Palmer Archipelago, p. 14) under the name of Montacuta 

 Christenseni. In my work of 1910, p. 73, I stated that, according to information given 

 me by Mr H. Lynge, it should belong to the genus Lepton} This apparent discrepancy 

 is due to the fact that two different sorts of bivalves are found commensally on this 

 Spatangoid. By far the commoner is the Lepton, with perfectly smooth valves. The 

 Montacuta with radiating ribs, as described by Grieg, I have found only on the specimen 

 from St. 142. I have not found both the commensals together on the same specimens of 

 the sea-urchin. The Lepton in particular often occurs in great numbers, almost filling up 

 the petals, and the apical system is often completely covered by them. The tests of the 

 Lepton are so exceedingly thin as to leave no trace when the specimens are dried. That 

 this is not due to the preserving fluid having been acid is evident from the fact that the 

 finest details of the valves of the pedicellariae are intact. 



Very young specimens of this Echinoid, when found isolated, are not identifiable with 

 complete certainty; this applies, for example, to the specimens from Sts. 140 and 148 



1 Bernasconi (op. cit., p. 16) also records such bivalves, and these were identified by Professor Duello 

 Jurado as belonging to the genus Lepton. 



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