356 



THE VOYAGE OF H.M.S. CHALLENGER. 



Abactinal plates not forming regular longi 



plates 



b. With no median radial series, 

 tudinal series. 



a. Abactinal area devoid of plating. Actinal intermediate 



forming isolated bands in transverse series .... Tylaster. 



b. Abactinal area plated. Actinal area with large intermediate plates. 



a. Plates covered with membrane ; usually devoid of spines or 



only rare isolated ones present ..... Porania. 

 /3. Plates usually spinous, or with the whole membrane closely 

 crowded with miliary spinelets. 



i. Margin angular, formed entirely by the infero- 

 marginal plates. Supero-marginal plates hidden 

 and inconspicuous. 



1. Infero-marginal plates with a flattened comb 



of spinelets, which form a broad marginal 



fringe ....... Marginaster. 



2. Spines when borne on the marginal plates 



grouped and inconspicuous, not forming 

 a marginal fringe. 



1. Papulas single and isolated. Adarn- 



bulacral armature on the actinal 

 surface of the plate in a grouped 

 or double series . . . Rhegaster. 



2. Papulae grouped. Adambulacral 



armature on the actinal surface of 

 the plate in a single series . . Poraniomorplia. 

 ii. Margin thick. Supero-rnarginal and infero-mar- 

 ginal plates superposed. Supero-marginal plates 

 well-developed and conspicuous, subequal to the 

 infero-marginal plates Lasiaster. 



Genus Gymnasteria, Gray. 



Asterope, Miiller and Troschel, Monatsber. d. k. Akad. d. Wiss. Berlin, April 1840, p. 104 (non 



Philippi, 1840). 

 Gymnasteria, Gray, Ann. and Mag. Nat. Hist., 1840, vol. vi. p. 278. 

 Asterojosis (pars), Miiller and Troschel, System der Asteriden, 1842, p. 62. 



This genus was first recognised by Miiller and Troschel in 1840 under the name of 

 Asterope, the Asterias carinifera of Lamarck being the type form. The name Asterope, 

 however, was employed by Philippi in the same year for a Crustacean genus, and was not 

 again used by Miiller and Troschel. In their System der Asteriden, published in 

 1842, the same type was referred to a new genus named Asteropsis, and with it were 

 associated the Asterias pulvillus of O. F. Miiller and the Asterias vernicina of Lamarck. 

 These three forms, however, constitute the types of three distinct genera, two of which 

 were established by Gray in 1840 under the names of Gymnasteria and Porania, 

 Asterias carinifera of Lamarck being referred to the former, and Asterias pulvillus, 

 O. F. Miiller, to the latter. Gray's names have consequently priority and are now 



