140 DISCOVERY REPORTS 



Mr D. Dilwyn John very kindly examined the type specimen and made camera lucida 

 drawings of the armature of 4 adambulacral plates distributed along the ray from the 

 fourth to thirty-eighth. These drawings as well as' his accompanying notes indicate that 

 the figures of the type are not quite correct. In the type, the furrow spines are com- 

 pressed, perhaps less so than in the Marion Island specimen; the distal spine is more 

 prominent into the furrow and is also slightly stronger and longer than the other, and 

 grows progressively more so from the base of ray toward tip. The furrow spines are 

 followed by 3 pairs of spines (varying 5-7), essentially as in the Discovery specimen. 

 This total of 8 spines, varying 7 or 9, holds all along the ray of the type, at least as far as 

 the thirty-eighth plate. At this point in the Discovery specimen, there are 8-10 spine- 

 lets, apparently longer than in the type. But the increasing prominence of one of the 

 furrow spines is characteristic. In this specimen there are 75 adambulacral plates and 

 the thirty-eighth is at about middle of ray measured on side. It is beyond the sixtieth 

 plate that the spinelets increase, sporadically, to 10 or 12; the distal 4 or 5 plates have 

 5 or 6 spinelets, there being obviously one furrow spinelet ; the other is squeezed behind 

 it, as in the type. 



The mouth-plates each have 4 heavy spatulate marginal spines, increasing in length 

 toward the oral angle, and 7 or 8 suborals graduated in size as are the subambulacrals. 



Ambulacral furrows narrow ; tube-feet strictly biserial with large sucking disks. 



Remarks. In general appearance this species resembles fiisciis and charcoti, but 

 differs from both in the greater number of adambulacral spines. The Discovery specimen 

 differs from the type in minor details which may represent normal variation of the 

 species, of which only two examples are known. 



Perknaster sladeni (Perrier) 



(Fig. B, 3-3 c, 4-4C; Plate VII, fig. i) 



Cribraster sladeni Verrier, 1891, p. 104, pi. 11, figs, za, 26.— Koehler, 1912, p. 39, pi. 2, fig. 12; pi. 

 6, fig. 6. 

 St. 182. Schollaert Channel, Palmer Archipelago, 278-500 m., i specimen. 

 St. 474. One mile west of Shag Rocks, South Georgia, 199 m., i specimen. 



In general appearance this form is closely similar to the ftiscus-antarcticus-georgianus 

 series but has the highest paxillae, smallest disk, and smallest actinal interradial areas. 

 The elongation of the pedicels of the abactinal plates which differentiates georgianiis 

 iromfuscus and antarcticiis is carried still further. The abactinal and actinal spinelets are 

 longer than in any Perknaster of comparable size, are slender, terete, only slightly 

 clavate and have the fewest thornlets at the distal end. 



The more typical specimen (Fig. B, 3-3 c) from St. 474 measures R 50 mm., r 14 mm., 

 R = 3-5 r; br 16 mm. The compact ovary has short lobes full of eggs measuring i mm. 

 in diameter (11 November 1930). 



The disk is high, the rays well arched, almost circular in section, and there is no 

 obvious lateral margin, although with care the marginal plates can be recognized by 



