REPORT ON THE ASTEROIDEA. 367 



Genus Rhegaster, Sladen. 

 Rhegaster, Sladen, Trans. Roy. Soc. Edin. 1883, vol. xxxii. p. 155. 



Marginal contour subpentagonal ; rays slightly produced. Abactinal surface more or 

 less convex, actinal flat. The whole body covered with membrane beset with crowded 

 spinelets. 



Abactinal skeleton composed of irregular plates, crowded and subimbricated in places, 

 which leave small irregularly disposed meshes. The whole skeleton hidden in a thick 

 membrane, and furnished with a compact covering of small, uniform, crowded spinelets. 

 Papulae small, numerous, isolated, irregularly distributed over the whole area. 



Iufero-marginal plates large, forming the margin of the test. Supero-marginal plates, 

 superficially invisible, concealed in the abactinal membrane. 



Actinal interradial areas with large subregular plates, hidden by a superficial mem- 

 brane, with small crowded spinelets. 



Adambulacral plates broader than long. Adambulacral armature consisting of short 

 spines thickly invested with membrane, which form a regular furrow series, and several 

 subregular longitudinal rows externally. Tube-feet in simple pairs, with a small sucker 

 disk. 



Madreporiform body small, midway between the margin and the apex. 



No pedicellarise. 



Remarks. — This genus was established for the reception of a starfish dredged during the 

 " Triton " cruise ; and I have also referred to it the form which was named by Stuxberg * 

 Solaster tumidus, but which was afterwards ranked as an Asterina by Danielssen and 

 Koren. 2 



Through the kindness of Professor Loven, I have had the privilege of examining Dr 

 Stuxberg's type specimens in Stockholm, and I entirely agree with Drs Danielssen and 

 Koren in regarding the original reference of the form to Solaster as altogether untenable. 



Clwrology of the Genus Rhegaster. 



«. Geographical distribution : — 



Atlantic : Two species between the parallels of 60° and 85° N. 



Rhegaster tumidus off Nova Zembla, Spitzbergen, the coasts of 

 Norway and Siberia. A variety (tuberculata) has been described by 

 Danielssen and Koren which occurs between Norway and Spitzbergen. 

 Rhegaster mur>rayi in the Faeroe Channel. 



1 Ofversigt K. Svensk. Vet.-Alcad. Forhandl., Arg. 35, 1S78 (1879), No. 3, p. 31, pi. vi. 



2 Nyt Mag. f. Nalurvidemlc, Bd. xxvi. Hft. 2, p. 182, pis. i. & ii. figs. 6-10. 



