ASTEROIDEA 219 



formed adambulacral plates; the long needle-like subambulacral and marginal spines, 

 with their characteristic sacculate sheaths; the variable but always non-reticulate 

 abactinal skeleton of the rays ; the presence of only crossed pedicellariae. 



The genus Rathbtmaster is notable for the suppression of the alternate superomarginal 

 plates and the reduction of the abactinal skeleton to spaced circular plates without 

 trace of connectives. The marginal and abactinal plates bear an acicular spine sur- 

 rounded by a retractile sheath with an expanded distal crown covered with numerous 

 pedicellariae. The ambulacral, adambulacral, and oral plates are similar to those of 

 Coronaster. 



In Labidtaster, Coronaster, Rathbumster, and certain genera of the Brisingidae there 

 are 2 gonads to each ray ; each gonad opens upon the side of the ray at some distance 

 from the base. All three genera, as well as the Brisingidae, have a single ampulla to each 

 tube-foot. 



Genus Labidiaster Liitken 



Labidtaster Liitken, Videmkab. Medd. natiirh. Foren. i Kjobenhavn, 1871, p. 289. Type L. radiosus 



Liitken. 

 Labidiastrella Verrill, 1914, p. 352. Type L. annulatus Sladen. 



Labidiaster annulatus Sladen 

 (Fig. I, 3-3^) 

 Labidiaster ammlatus Sladen, 1889, p. 595, pi. 108, fig. i.— Koehler, 1917, p. 7, pi. i, figs. 2, 4, 5. 

 Labidiaster radiosus Koehler, 1906, p. 24. — 1912, p. 7, pi. i, fig. i. 

 Labidiastrella anmilata Verrill, 1914, pp. 352, 373. 



St. 148. Off Cape Saunders, South Georgia, from 54° 03' S, 36° 39' W to 54° 05' S, 36° 36' 30" W, 

 132-148 m., grey mud and stones, 2 specimens. 



St. 156. South Georgia, 53° 51' S, 36° 21' 30" W, 200-236 m., rock, 2 specimens. 



St. 159. South Georgia, 53° 32' 30" S, 36° 08' W, 160 m., rock, i specimen. 



St. 160. Near Shag Rocks, 53° 43' 40" S, 40^ 57' W, 177 m., grey mud, stones, 4 specimens. 



St. 167. Off Signy Island, South Orkneys, 60° 50' 30" S, 46° 15' W, 244-344 m., green mud, 

 1 specimen. 



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



St. 187. Neumayr Channel, Palmer Archipelago, 64° 48' 30" S, 63° 31' 30" W, 259 m., mud, 



1 specimen. 



St. 190. Bismarck Strait, Palmer Archipelago, 64° 56' S, 63° 35' W, 93-130 m., rock or stones and 

 mud, 8 specimens. 



St. 371. I mile east of Montagu Island, South Sandwich Islands, 99-161 m., 3 specimens. 



St. MS 68. East Cumberland Bay, South Georgia, 220-247 m., 2 specimens. 



St. 1873. Off Clarence Island, South Shetland Islands, 61° 20-8' S, 54° 04-2' W, 200-137 m., 



2 specimens. 



St. 1955. South Shetland Islands, 61° 35-1' S, 57° 23-3' W, 440-410 m., 2 specimens. 



The smallest specimen (St. 160), with R 15-17 mm. and r4mm., has 16 subequal 

 rays and the bud of a new one. The specimen with longest rays (St. MS 68) with 

 R 340-370 mm. and r 45 mm. has 45 rays. Of these, 21 are only 15-50 mm. long and 

 represent regenerating rays from margin of disk. The following are the maximum 

 number of rays observed: 47 rays, R 270 mm. (St. 156) ; 48 rays, R 260 mm. (St. 167) ; 



