ASTEROIDEA 143 



spinelets oi georgianus are neither those of antarcticiis nor sladeni but nearer to the latter 

 as are the small actinal interradial areas. 



Type locality. Falkland Islands. 



Distribution. Falkland Islands, Shag Rocks, Palmer Archipelago; 199-500 m. 



Perknaster sladeni georgianus subsp.nov. 

 (Fig. B, 2-26; Plate V, fig. 2; Plate VI, fig. 3) 



Diagnosis. Differing from typical antarcticiis in having an obviously higher tabulum 

 to abactinal plates, slenderer abactinal spinelets which are less swollen at tip and have 

 less prominent thornlets ; actinal paxillae higher and usually more closely placed. Type, 

 R 31-35 mm., r 10-5 mm., br 12 mm. R = 3r. 



Description. Although the 3 specimens are small (R 33 mm. to R 35 mm.) they 

 are sexually mature. The race is in some respects intermediate between sladeni and 

 atitarcticus. It is not close to fiiscus since the pedicels of the paxillae are decidedly 

 higher (0-4 mm.), while the abactinal and actinal spinelets are slenderer and differently 

 armed. 



The abactinal paxillae are also higher than in antarcticiis owing to the higher tabulum 

 which with plate measures 0-4 mm., while the spinelets measure o-48-o-54 mm. In 

 antarcticiis the tabulum measures 0-23-0-27 mm. high and the spinelets 0-45-0-5 mm. 

 When the spinelets are upright on the tabulum, the paxillae of georgianus are o-88- 

 0-94 mm. high (including the somewhat thinner abactinal integument) while those of 

 antarcticiis are 0-68-0-77 (including a somewhat thicker skin which further shortens the 

 apparent height of the paxillae). These differences seem small but are very apparent 

 when specimens are compared under low magnification. As will be noted from the 

 figures, the abactinal spinelets oi georgianus are slenderer and not at all capitate as are 

 those of antarcticiis. In this respect they stand nearer to the spinelets of sladeni. 



The inferomarginal plates do not form a conspicuous actinal interradial arc as in 

 aurorae. The plates can be distinguished from the actinals only by their slightly more 

 numerous spinelets — 5-7 in the interradial region, while the actinal plates adjacent 

 carry 2 or 3 . The actinal interradial areas are about as small as those of sladeni, and smaller 

 than is apparent from the size of disk, since the interradial width of area is only about 

 three-fourths minor radius. The inferomarginals are actinal in position, one-fourth r 

 from ambitus. A few of the plates near furrow have their 2-4 slender spinelets slightly 

 bent and co-ordinated into a pedicellaria, especially in specimens from St. 42. 



In sladeni, from St. 474, the adambulacral furrow spinelet and often the second spinelet 

 are compressed, while in georgianus they are subterete, rather slender, tapered, with 

 occasionally a slight compression of the tip of the furrow spinelet (St. 42). Otherwise the 

 adambulacral armature is fundamentally as in sladeni and fusciis. There are 3 spines in 

 an oblique transverse series, the furrow spine being on the aboral side of plate. But the 

 outer, smallest spinelet sometimes has an aboral companion, making 4 in all. This fourth 

 spine sometimes stands aborad to the second spine of series. The first adambulacral 



