ASTEROIDEA 131 



not significant. The marginal plates are very variable in size and armature. In forma 

 elect His (in its broadest sense) they may be small and similar in form and armature to 

 those of Ganeria. 



The mystery of Lebrunaster paxillosus Perrier appears to be solved by three specimens 

 from St. 55. The type and only knov^rn specimen of Lebrunaster was collected at Santa 

 Cruz, Argentina, where both Cycethra and Ganeria occur. Our two largest specimens 

 have R 22 mm., r 9 mm. and have small spaced marginals, like those of Ganeria, which 

 carry 2 transverse series or in some cases only i series of spinelets. The actinal plates 

 carry 2 or 3 rather short spines, about the size of the marginal spines. Lines run from 

 margin to ambulacral furrow across the actinal area. The abactinal plates are those of 

 Cycethra and carry in one specimen 3-6 spinelets in a fasciculate group ; but in the other 

 specimen there are only 2 or 3 spinelets; groups well spaced. Two other specimens (St. 

 WS 84, R 26 mm., St. WS 85, R 25 mm.) are also " Lebrunaster'' but the small marginals 

 are less carinate, more typically Cycethra, and the adambulacral armature is like that of 

 Perrier's fig. 4c (189 1, pi. 9) which of course is typical of Cycethra. The actinal plates 

 carry 3 or 4 short spinelets. The abactinal surface of the specimen from St. WS 85 

 shows, slightly, the irregularity of the plates of the radial area characteristic of Ganeria. But 

 the actinal surface of both specimens is that of Cycethra, whereas in the three specimens 

 from St. 55 the actinal surface (but not abactinal) would pass for that of an aberrant 

 Ganeria with short spines, especially as the marginal plates are those of Ganeria. It was 

 probably the Ganeria-like marginal plates which led Perrier at the end of his description 

 oi Lebrunaster paxillosus to say "voisine de Ganeria". 



In a fourth specimen, from St. 55 (R 39 mm.), the armature of the adambulacral and 

 actinal plates is that of Ganeria. The marginal plates have well-spaced tabula bearing 

 the equivalent of 2 transverse rows of spines (7 or 8 in all) but in a few cases the spinelets 

 form a fasciculate group with one in the centre. The abactinal surface carries small, 

 uniformly spaced, fasciculate groups of 4 or 5 spinelets, without any irregularity of 

 plates on the radial region. It is therefore Cycethra. These curious specimens, exhibiting 

 in diflFerent degrees the characters of Ganeria and Cycethra, may be hybrids and suggest 

 a possible explanation of Lebrunaster. No typical Ganeria falklandica was taken at 

 St. 55 ; but at St. WS 85 a small specimen of iorma falklandica and a large one of forma 

 hahni were dredged, along with Cycethra and that example of ''Lebrunaster" havmg a 

 slight distortion of the radial abactinal plates. 



These aberrant Cycethra (except the specimen from St. 55 which is most Ganeria- 

 like) would fall in forma electilis. Sladen's figures (1889, pi. 60, figs. 3, 4) of the type 

 are not very different from Perrier's figures of Lebrunaster. The marginal armature is 

 spaced. 



Whatever the cause of these curious variations, I believe that the type of Lebrunaster is 

 an example of them and does not represent a valid genus, or species. 



Remarks on Antarctic specimens. There are 7 specimens ranging in size R 25 mm. 

 to R 75 mm. Thirteen young vary from R 6-5 mm. to R 14 mm. A specimen of the 

 first group from East Cumberland Bay (St. MS 68) resembles in a general way a slender- 



