REPOET ON THE ASTEROIDEA. 375 



Asterinidae the genera Porania, Dermasterias, and Asteropsis, which are now placed 

 in the family Gymnasteriidae. I maintain the composition of the family Asterinidae as 

 defined by Perrier 1 in 1875. 



In addition to the genera enumerated by him I have included Cycethra, a form since 

 described, whose structural characters seem to me to place it amongst the Asterinidae. 

 I have also added in the following list another genus, Steg master (n. gen.), which seems to 

 me necessary. The type of Stegnaster is the starfish described by Hutton 2 under the 

 name of Pteraster injiatus, and subsequently placed under Palmipes by Perrier. 3 I 

 consider that the disposition of the papulae, the membranous investment of the abactinal 

 area (with the absence of the characteristic tufts of spines and the presence of granules), 

 and the simple character of the armature of the adambulacral plates are sufficient to 

 warrant the generic separation of this form from Palmipes. I also refer to the same 

 genus Asterina ivesselii, though not without some hesitation, as the examples I have seen 

 of that species appear to me to be immature forms. 



So far as I can judge from the description 4 and figure 5 of Tremaster given by Verrill, 

 I consider that the genus also belongs to this family, but from want of knowledge of its 

 structure, I am unable to say whether its affinities are nearest to Palmipes or Asterina. 

 No remark is made by the author as to the function of the extraordinary interradial 

 apertures, and no suggestion is offered as to whether they are in relation with papular 

 organs, or lead to a nidamental cavity. The circumstance of their opening on both the 

 abactinal and actinal surfaces would seem to be at variance with such a supposition. 



Synopsis of the Genera included in the Family Asterinidae. 



A. Marginal plates large ; and superficially phanerozonid in character . . Ganeriin.e. 



a. Spinelets on the abactinal plates spiniform, disposed in paxillas-like 



groups. No differentiated median band ; all the abactinal 

 plates subsimilar. Marginal plates with a vertical group of 

 spinelets. Actinal intermediate plates 'with small groups of 

 spinelets Cycethra. 



b. Spinelets on the abactinal plates small, often in arcuate series. A 



more or less distinctly defined band of slightly differently shaped 

 plates along the median radial line. Marginal plates with a 

 vertical single series of spines forming a sort of comb. Actinal 

 intermediate plates with large spines (1-2) not forming a 

 group Ganeria. 



1 E6vis. Stell. Mus., p. 28 (Archives de Zool. exper., 1875, t. iv. p. 292). 



2 Cat. Echin. New Zealand, 1872, p. 10. 



3 Revis. Stell. Mus., p. 291 (Archives de Zool. exper., 1876, t. v. p. 211). 



4 Proc. U.S. Nat. Mus., 1879, Nov., p. 201. 



6 Rep. Commiss. Fish and Fisheries for 18S3, Washington, 1885, pi. xviii. fig. 51. 



