ASTEROIDEA 133 



I believe these young are especially valuable in indicating the close relationship 

 between Cycethra and Perhiaster. 



Distribution. Characteristic of the Falkland-Magellan fauna; north to 45° 20' S on 

 the Pacific Coast of South America, and to 40^ 40' S on the Atlantic coast; to 55° S 

 on the coast of Tierra del Fuego. Low water to 267 m. 



Shag Rocks; South Georgia; South Orkneys; South Shetlands; south to Marguerite 

 Bay, 67° 43' S (Koehler, 1912). 



Doderlein has recorded a very young specimen from Observation Bay, Kerguelen, 

 near the type locality of Perkfiaster densus. 



Genus Perknaster Sladen 



Perknaster Sladen, 1889, p. 550. Type P.fuscus Sladen. 



Cribraster Perrier, Comptes Rendiis, cvi, no. 11, 1888, p. 675 (nomen nudum). — 1891, p. 104. Type C. 



sladetii Perrier. 

 Cryaster Koehler, 1906, p. 24. Type C. antarcticus Koehler. 

 Cribellopsis Koehler, 1917, p. 36. Type C. ralUeri Koehler. 



The sea stars of this characteristic Antarctic and sub-Antarctic group are closely allied 

 to Cycethra despite the decidedly peculiar and specialized structure of fully grown 

 specimens. With increasing age the body wall thickens, while in varying degree the 

 abactinal skeleton degenerates. In extreme cases the plates and even spinelets disappear. 

 The glandular skin proper is thick, pulpy, and thrown into a myriad of tiny folds and 

 pustules (at least in alcoholic specimens). Immersed in this maze of wrinkles and 

 papillae are numerous small papulae and the small paxillae. In alcoholic specimens the 

 latter are often difficult to distinguish, since their sacculate investment closely resembles 

 the skin pustules and may not rise above the general level. 



In 1906 Koehler described the first of the three species upon which he founded the genus 

 Cryaster and the family Cryasteridae. In subsequent monographs he further elaborated 

 Cryaster antarcticus and described C. charcoti and C. aurorae, as well as Perknaster 

 aurantiaciis. Examination of an authentic specimen of Perknaster fiisciis Sladen, type 

 of the genus, clearly demonstrates that all of Koehler's species of Cryaster are typical 

 Perknaster, which obviously has priority. It will be necessary to examine the detailed 

 structure of P. aurantiacus to determine whether it is distinct from P. sladeni (Perrier). 



In the Discovery collection is a fairly representative example of the latter species 

 which Perrier described as Cribraster sladeni, from a single specimen taken near the 

 Falkland Islands. It is obviously of the same genus as fuscus and antarcticus, from which 

 it differs inter alia in having tall, slender paxillae. It penetrates to high latitudes and is 

 found along with antarcticus in the Palmer Archipelago. It cannot therefore be re- 

 garded simply as a northern outpost race of antarcticus. 



Perknaster contains the following nominal species in order of naming : 



fuscus Sladen 1889. charcoti (Koehler) 1912. 



densus Sladen 18S9. aurantiacus Koehler 1912. 



sladeni {Ferner) i8gi. m/rorae (Koehler) 1920. 



antarcticus (Koehler) 1906. georgianus nov. 



