262 DISCOVERY REPORTS 



Smilasterias triremis Sladen 



Asterias (Smilasterias) triremis Sladen, 1889, p. 578, pi. loi, figs. 5, 6; pi. 102, figs. 5, 6. 

 Smilasterias triremis Fisher, 1930, p. 239. 



St. 181. Schollaert Channel, Palmer Archipelago, 160-335 '^•' mud, 2 specimens. 



St. 187. Neumayr Channel, Palmer Archipelago, 259 m., mud, i specimen. 



St. 190. Bismarck Strait, Palmer Archipelago, 93-130 m., rock or stones and mud, 2 specimens. 



The smallest specimen measures R 40 mm., r 7 mm., br 8 mm. ; the largest measures 

 R 61 mm., r 7 mm., br 8-10 mm. All are therefore larger than the type which has 

 R 35 mm., r 5-5 mm. Treatment with caustic potash reveals a single series of small 

 actinal plates which extend as far as seventh to tenth inferomarginal plate — or about one- 

 fifth length of ray. They are normally spineless but sporadically one of the proximal 

 plates of the series carries a small spinelet. In the largest specimen the first few infero- 

 marginals carry irregularly 2-4 spines ; throughout rest of ray, 3 flat, truncate, chisel- 

 shaped spines. In the other specimens there are usually 3, but occasionally 2, spines. The 

 adambulacral plates are diplacanthid as a rule, but here and there a plate with 3 spines 

 occurs. Obviously the actinolateral region is less spiny than in scalprifera. Direct com- 

 parison of specimens shows that the marginal spines of triremis are markedly longer and 

 broader, and the adambulacral spines are longer and more robust than those of scal- 

 prifera. Dorsally the two species are similar in appearance, actinally very distinct. 

 Attached to the furrow face of the adambulacral plates near base of innermost spine are 

 numerous pedunculate lanceolate straight pedicellariae which, in scalprifera, are about 

 0-6-0-75 mm. long, and, in triremis, only 0-25-0-3 mm. 



In triremis the lanceolate straight pedicellariae which are liberally scattered on the 

 actinal and marginal areas, and more sparingly on the abactinal plates, are subequal in 

 length to the crossed pedicellariae. There are regularly no enlarged pedicellariae in the 

 actinal interradial areas. In scalprifera there are conspicuously large lanceolate actinal 

 interradial straight pedicellariae. A definite row of actinal and scattered inferomarginal 

 straight pedicellariae are usually obviously larger than the crossed; very few supero- 

 marginal and abactinal straight pedicellariae. 



Crossed pedicellariae are similar to those of scalprifera and measure o-27-o-3i mm. 

 in length and o-i8 mm. broad. 



The species has heretofore been known only from the type series taken in 150 

 fathoms, between Kerguelen and Heard Islands, coarse gravel, bottom temperature 

 35-2 F. Its capture in the Palmer Archipelago indicates that it is an antarctic species, 

 in contrast to scalprifera which is subantarctic. 



Genus Cosmasterias Sladen 



Cosmasierias Sladen, subgenus, 1889, p. 576. Type Asteracanthion sulcifer Perrier = ^. luridum 



Philippi. — Fisher, 1930, p. 227. 

 Diplasterias Perrier, part, 1891, p. 77. — Meissner, 1904, p. 6. 

 Comasterias Perrier, 1891, p. 159. 

 Podasterias Perrier, 1891, p. 160. 

 Quadraster Perrier, Res. camp. Prince de Monaco, 1896, p. 27. Type Stichaster felipes Sladen. 



