REPORT ON THE ASTEROIDEA. 355 



Family Gymnasteriid^e, Perrier, 1884. 



The older known genera included in this family were originally classed by Perrier l in 

 the Goniasteridos. They w r ere subsequently removed by Viguier, 2 with the exception of 

 Gymnasteria, to the Asterinidse. Latterly, in the new classification proposed by M. 

 Perrier, 3 they were separated as an independent family, Gymnasteria being taken as the 

 type form and again united with the genera which were separated from it by Viguier. 



I fully concur in the course adopted by Perrier and maintain the family as established 

 by him, notwithstanding the fact that more than one of the recently discovered genera 

 appear to diminish considerably the difference supposed to exist between the Gymnas- 

 teriidas and Asterinidse. 



I have added several genera to those ranked by Perrier in the Gyrnnasteriidee, and 

 of these one or two have unquestionably many affinities with the Asterinidse ; but the 

 balance of their structural " points " seems to me to warrant their classification with the 

 Gymnasteriidge. To those who take the broad view of taxonomic relationship inseparable 

 from a theory of descent involving the assumption of organic form being dependent on 

 variation and adaptation, this interlocking, as it might be termed, of allied families need 

 not, in my opinion, invalidate the acceptance of the independent existence of two types 

 or families, because some of their component forms show intermediate and transitional 

 characters. This, indeed, seems to me to be a case which might be expected to occur 

 under favourable circumstances ; although in general these intermediate phases have dis- 

 appeared. 



Synopsis of the Genera included in the Family Gymnasteriim;. 



A. Marginal and abactinal plates devoid of spines. 



a. Abactinal plates irregular or substellate, not forming a composite reticulated 



mesh-work. Adambulacral armature : furrow series consisting of two 

 spines; actinal spines one or two. Marginal plates large. A pair of 

 specially localised pedicellarise at the base of the rays on the abactinal 

 surface Asteropsis. 



b. Abactinal plates forming a composite reticulated mesh-work. Adambulacral 



armature : furrow series consisting of one spine ; one actinal spine. Mar- 

 ginal plates small, pear-shaped, obliquely placed and strongly imbricating. 

 No localised pedicellarise at the base of the rays ..... Dermasterias. 



B. Marginal plates with spines. 



a._With a medio-radial series of large spines. Supero-marginal plates forming 

 the margin, bearing large isolated spines. Abactinal plates rounded, 

 forming regular longitudinal series ....... Gymnasteria. 



1 Revis. Stell. Mus., p. 27 {Archives cle Zool. exper., 1875, t. iv. p. 291). 



2 Archives de Zool. exper., 1878, t. vii. p. 201. 



3 Now. Archives Mus. Hist. Nat., 2e Ser., 1884, t. vi. p. 165. 



