ASTEROIDEA 117 



Family GONIASTERIDAE Verrill 



Genus Pseudarchaster Sladen 



Pseudarchaster discus Sladen 



Pseudarchaster discus Sladen, 1889, p. no, pi. 19, figs, i, 2; pi. 42, figs. 3, 4. 

 Astrogonium patagonictm Perrier, 1891, p. 125, pi. 13, figs, za, 2b (Beagle Canal). 



St. WS 781. 50° 30' S, 58° 50' W, 148 m., I specimen. 

 St. WS 782A. 50° 29^' S, 58° 23I' W, 141-146 m., I specimen. 

 St. WS 805. 50° loj' S, 63° 29' W, 148 m., 2 specimens. 

 St. WS 850. 51° i8f' S, 63° 30I' W, 57-166 m., I specimen. 



The specimens are large compared to the type, R ranging from 55 to 60 mm., whereas 

 the type has R 30 mm. The post-adambulacral fascioles described by Sladen are 

 present. Along the transverse margins of the actinal plates adjacent to adambulacrals, 

 the spinelets, which are smaller than those of the rest of surface, bend over the sutural 

 groove and touch similar spinelets of adjacent plate, forming a crude pectinate pedicel- 

 laria. These are most apparent or best differentiated near the mouth plates, where each 

 comb has about 7 spinelets. There is an unpaired pedicellaria at outer end of mouth- 

 plates ; and a similar co-operation is apparent between the outer marginal adambulacral 

 spinelets and adjacent actinal intermediate spinelets, aUhough these combs are not so 

 regular as the transverse ones. 



As in other species of Pseudarchaster of which a series is known, specimens may be 

 divided into two groups. In the one the rays are shorter and the marginal plates are 

 shorter and broader than in the other, but there is no significant difference in the number 

 of marginal plates (34-35)- 



Astrogonium patagonicum Perrier seems to me to be specifically the same as discus and 

 to be referable to the slender-rayed variety. On the right side of Perrier 's fig. 2b one 

 can see, with a lens, an indication of the pectinate pedicellariae. In his list of sub- 

 Antarctic echinoderms, Koehler (1912, p. 211) lists both Astrogonium patagonicimi and 

 Pseudarchaster discus as peculiar to the Magellan fauna, although he was certainly aware 

 that the generic names are synonymous. 



The persistent misuse of Astrogonium in France is a curious case of misguided 

 loyalty to Perrier who started the vogue by appropriating a name, which never had any 

 status, for a group of species {Pseudarchaster and Aphr adit aster) none of which was listed 

 in the original description of Astrogonium (Miiller & Troschel, 1842, p. 52) for the 

 obvious reason that none was known in 1842. Yet in 1894, five years after Pseudarchaster 

 was published with figures, Perrier substituted Astrogonium. 



MuUer and Troschel in their System der Asteriden, 1842, established Astrogonium, 

 without type, for 4 described genera, now in current use, namely Hippasteria, Goniaster, 

 Pentagonaster, Tosia. If one adopts the first species as type, then Astrogonium was a 

 synonym of Hippasteria Gray, 1840; if the oldest generic name included in the group, 

 then Astrogonium is a synonym of Goniaster Agassiz, 1835. As stated above, no species of 



