442 THE VOYAGE OF H.M.S. CHALLENGER. 



Family Solasterice, Perrier, 1884. 



Notwithstanding the remarkable and in many respects archaic characters of the 

 o-enera Solaster and Crossaster, they have until quite recentty been classed with the 

 Echinasteridse. The discovery of deep-sea forms more or less closely allied has, however, 

 excited closer attention, and in 1884 Perrier 1 established the family Solasteridae, which 

 comprised Korethraster, Lophaster, Radiaster, Ctenaster, Solaster, and Crossaster. 



With this classification I fully concur, reserving only any expression of opinion as to 

 the validity of the position of Radiaster and Ctenaster in this family, in consequence of 

 my want of knowledge of the structure of the forms in question. I have on these grounds 

 not included them in the following table. 



I have added to the family two new genera, Peribolaster and Rhipidaster, the former 

 approaching Korethraster in its affinities and the latter Crossaster. 



Synopsis of the Genera, included in the Family Solasteridae. 



A. Armature of the adambulacral plates in two series at right angles to each 



other . SoLASTERiNa:. 



a. No actinal intermediate plates along the ray. 



a. With one series of well-developed marginal paxillae. 



a. Abactinal structure reticulate. With widely spaced peni- 



cillate paxillae. Papula; numerous ..... Crossaster. 



/3. Abactinal structure formed of stellate plates. With small 



closely crowded paxillse. Papulae single or few . . . Solaster. 



b. With two series of well-developed marginal paxilke .... Lophaster. j 



b. A continuous series of actinal intermediate plates along the ray, each of 



which bears an obliquely placed comb of spines Rhipidaster. 



B. Armature of the adambulacral plates forming with that of the actinal inter- j 



mediate or infero-marginal plates a single transverse series . . Korethrasterin.e. 



a. Abactinal plates polygonal or rounded in outline. The spines compos- 



ing the paxilliform tufts naked and free Korethraster. 



b. Abactinal plates cruciform ; forming wide meshes. The spines com- 



posing the paxilliform tufts in membranous sacs which are united 



together in the interior of the group ....... Peribolaster 



Subfamily Solasterin^;, Sladen, 1888. 



Genus Crossaster, Miiller and Troschel. 



Crossaster, Miiller and Troschel, Monatsber. A k. preuss. Akad. d. Wiss. Berlin, 1840 (April), p. 103. 



The question of the validity of recognising Crossaster, Solaster, and Lophaster, as 

 independeut genera, has been so fully discussed by recent writers, that I do not propose 

 to touch upon the subject further than to state that I maintain the three genera as 

 1 Nouv. Archives Mtis. Hist. Nat., 18S4, 2e Serie, t. vi. p. 164. 



