196 DISCOVERY REPORTS 



Pt. orgentmiis Bernasconi is also closely related to lebruni. It has the characteristic 

 short paxillar pedicels and 3 (or 4) spinelets, one of which is longer than the others. 

 Adambulacral and oral spines 6, the suboral long, tapered, slightly curved. The three 

 known specimens have 6 rays. 



The type and only specimen of rugatus is obviously young, measuring R 9-5 mm., 

 r 6-5 mm. The form is pentagonal, paxillar spinelets 5-6; adambulacral spinelets 3 or 4; 

 oral spines 3, webbed, the two webs of a mouth angle separated ; suboral, longer than the 

 other oral spines, "exceedingly thick, translucent triangular". Supradorsal membrane 

 "indurated with minute spicules averaging o-o3-o-04 mm. in length, small, irregular, 

 and angularly branching bodies, subdendriform in appearance and fairly well spaced". 



A specimen of lebrtini measuring R 9 mm. and r 5 mm. is distinctly stellate with 

 angular interbrachia ; paxillae with usually 3 spinelets ; adambulacral spines 5 proximally ; 

 oral spines usually 5; suboral spine terminally triangular; actinolateral membrane 

 proximally much narrower than in rugatus and, unlike that of rugatus, it narrows very 

 gradually toward tip of ray. 



Pt. affinis Smith, Kerguelen (possibly including aculeatus Koehler), has 5-10 paxillar 

 spinelets, 4 adambulacral spines, 4 oral and a tricarinate (triangular) suboral. Both 

 affinis and aculeatus appear to have a thin supradorsal membrane, without spicules. 



Type locality of Pteraster lebruni. Magellan region: "Washington Canal", 



80 m. 



Distribution. Magellan and Falkland Plateau, to South Georgia on the east and 

 Bellingshausen Sea on the south-west (71° 24' S, 89° 12' W); 74-450 m. 



Pteraster lebruni brachiatus Koehler 



Pteraster brachiatus Koehler, 1917, p. 49, pi. 7, figs, i, 2, 6; pi. 10, figs. 6-10. 

 St. 1562. OflF Marion Island, 46° 52' S, 37° 55' E. 97-104 m., 7 specimens. 

 St. 1563. OflF Marion Island, 46° 48-4' S, 37° 49-2' E, 101-106 m., 3 specimens. 



The largest specimen (St. 1562) measures R 48 mm., r 15 mm., br 18 mm., height of 

 ray at base, 1 5 mm. The rays are narrower than in typical lebruni. The supradorsal 

 membrane is thick, rugose, and crowded with deposits. In this specimen the osculum is 

 as small as the diameter of a fine sewing needle, but in other specimens is well defined 

 though small. It is probable that the osculum nearly or quite disappears in some speci- 

 mens, as evidently happened in the case of a specimen of Pt. militaris from Bering Sea 

 which Ludwig named Pt. aporus and which later Verrill designated as the type of 

 Pterasterides. 



The pedicel of paxillae is appreciably slenderer than in typical lebruni and there are 

 ordinarily 3 or 4 slender paxillar spines of which one is slightly the heavier. Near the 

 osculum there are sometimes 5. 



What the photographs do not show clearly is that adambulacral combs have proximally 



7 spines and distally 6. As in lebrtini the web is continued across the actinolateral mem- 

 brane as a series of parallel folds. In each of the 2 marginal fans of each oral angle are 



8 spines while the suboral is heavy, clavate, with a sharp, prismatic hyaline tip. Small 



