ASTEROIDEA 93 



of the group may be in contact with the peristomial membrane. There is no sign of these 

 in Ripaster, Psilaster, or Bathybiaster . 



Koehler makes some point of the structure of the marginal plates. I can find no 

 difference between Ripaster and Psilaster, except that in Ripaster the vertical fasciolar 

 grooves of the marginal plates are a trifle shallower. These are the grooves, lined with 

 ciliary spinelets, which intervene (on the dorsoventral suture line) between the ridge- 

 like tabula of the marginal plates. Each ridge passes unbroken from supero- to infero- 

 marginal plate, and is homologous to the tabulum of the abactinal paxillae. 



Whether the more numerous superomarginal spines of Ripaster constitute a feature of 

 generic value must remain a matter of opinion. In Persephonaster (as in Astropecten) 

 superomarginal spines may be absent {Persephonaster cingulatus Fisher) or there may be 

 a vertical comb of them {P. luzonicus Fisher). The adults of all described species of 

 Psilaster have at least one superomarginal spine. 



My feeling is that charcoti is a rather aberrant Antarctic outpost of the cosmopolitan 

 Psilaster. 



Psilaster charcoti (Koehler) 

 Ripaster charcoti Koehler, 1906, p. 4, pi. 3, figs. 20, 21, 31, 32; 1908, p. 540; 1912, p. loi, pi. 8, 



fig. 2; 1920, p. 258, pi. 51, fig. 5; pi. 52, fig- 1; pi- 72. fig- I- 



Ripaster longispinus Koehler, 1920, pi. 51, figs. 5-8; pi. 52, figs. 2-4; pi. 72, fig. 2; 1928, p. 95, pi. 12, 

 figs. 6-8. 



St. 27. West Cumberland Bay, South Georgia, no m., 2 specimens. 



St. 30. West Cumberland Bay, South Georgia, 251 m., 2 specimens. 



St. 39. East Cumberland Bay, South Georgia, 179-235 m., grey mud, 5 specimens. 



St. 45. 2-7 miles S, 85° E of Jason Light, South Georgia, 238-270 m., grey mud, 4 specimens. 



St. 123. Off mouth of Cumberland Bay, South Georgia, 230-250 m., grey mud, 2 specimens. 



St. 140. Stromness Harbour to Larsen Point, South Georgia, 122-136 m., green mud, stones, 

 2 specimens. 



St. 148. Off Cape Saunders, South Georgia, 132-148 m., grey mud, stones, 2 specimens. 



St. 170. Off Cape Bowles, Clarence Island, 61° 25' 30" S, 53° 46' W, 242 m., rock, i specimen. 



St. 181. Schollaert Channel, Palmer Archipelago, 160-335 m., mud, 4 specimens. 



St. 182. Neumayr Channel, Palmer Archipelago, 259 m., mud, i specimen. 



St. 187. Neumayr Channel, Palmer Archipelago, 259 m., 2 specimens. 



St. 366. Four cables south of Cook Island, South Sandwich Islands, 77-152 m., i specimen. 



St. 371. One mile east of Montagu Island, South Sandwich Islands, 99-161 m., 4 specimens. 



St. 458. Seven miles S, 50° W of Cape Circumcision, Bouvet Island, 357-377 m., i very young 

 specimen. 



St. WS 27. South Georgia, 53° 55' S, 38° 01' W, 106-109 m., gravel, 2 specimens. 



St. WS 32. Mouth of Drygalski Fjord, South Georgia, 91-225 m., 3 specimens. 



St. WS 865. 50° 03' S, 64° 14' W, 126 m., 3 specimens. 



St. MS 68. East Cumberland Bay, South Georgia, 220-247 m., 3 specimens. 



St. 356. Terra Nova (loaned by British Museum, register 1914.8. 12. 17-18; labelled "Astenas 

 longstaffi" by Prof. F. J. Bell; an example of forma longispinus). 



St. 1660. Ross Sea, 74° 46-4' S, 178° 23-4' E, 351 m., 10 specimens (forma longispinus). 



St. 1952. Between Penguin Island and Lion's Rump, King George Island, South Shetlands, 367- 

 383 m., I specimen, R 163 mm., r 42 mm. (forma longispinus). 



St. 1957. Off south side of Clarence Island, South Shedands, 2 specimens (forma longispinus). 



D XX 



