238 Annals of the South African Museum. 



Cribriform organs* present in each interradius . . Porctllanasteridae. 



No cribriform organs. 



Marginal plates very spiny, more or leas alternate; papulae restricted to 

 special areas at base of rays .... Benthopectinidae. 



Marginal plates opposite ; papulae not restricted to special areas at base 

 of rays. 



Abactinal surface covered witb paxillae. 



Superornarginal plates well developed . Astropectinidae. 



Superomarginal plates aborted . . . Luidiidae. 



Abactinal surface not covered with paxillae. 



Disk large with big actinal interradial areas, but no actinal papulae. 

 Marginal plates large and conspicuous; disk more or less 

 flat; papulae single or a few together Goniasteridae. 



Marginale plates not conspicuous; disk elevated or at least 

 very thick ; papulae numerous in large groups. 



Marginal plates large; abactinal skeleton more or less 



conspicuous. .... Oreasteridae. 



Marginal plates small and with abactinal skeleton covered 



and concealed by a thick skin . . Poraniidat. 



Disk small with very small actinal interradial areas, or if the 



latter are well developed there are actinal papulae; marginal 



plates small; tegumentary developments, granulate (rarely wanting) 



Ophidiasteridae. 



Marginal plates small or wanting; abactinal skeleton more or less imbricated or 

 reticulate. 



Disk not circular and sharply set off from long, more or less terete, and 

 readily detachable arms; marginal plates small but regularly present (except 

 Cryasteridae). 



Pedicellariae rare or wanting, never pedunculate forcipiform; ambulacral 

 ossicles rarely crowded; pedicels usually in two series. 



Oral plates rather small, not shovel- or plowshare-shaped; ambu- 

 lacral furrows narrow. 



Marginal plates conspicuous; actinal plates regularly radiatingly 

 arranged .... . Ganeriidae. 



Marginal plates quite inconspicuous. 



Abactinal skeleton formed of closely imbricated plates, bearing 

 very small spineleta .... Asterinidae. 

 Abactinal skeleton not imbricate. 



Abactinal skeleton more or less reticulate 



Echinasteridae. 



Abactinal skeleton entirely aborted Cryasteridae. 

 Oral plates big and shovel- or plowshare-shaped; ambulacral furrows 

 wide. 



Abactinal skeleton with paxillae or pseudopaxillae, not concealed 

 by a supradorsal membrane . . . Solasteridae. 



* Technical terms used in this or subsequent keys are fully explained and 

 llustrated in Sladen's CHALLENGER report (1889) or in Fisher's North Pacific 

 Asteroids (Bull. 76 U.S.Nat. Mus , 1911). 



