ASTEROIDEA OF XORTH PACIFIC AND ADJACENT WATERS FISHER. 23 



KEY TO THE KNOWN GENERA OF PORCELLANASTERID^. 



a'. Cribriform organs highly developed, localized; actinal interradial areas without fimbriated trans- 

 verse channels; no superambulacral plates. 

 6'. noth inferomarginals and superomarginals present, 

 c'. Actinal intermediate plates usually but not always naked; adambulacral plates with a single 

 series of spines on furrow margin only; terminal plates large, armed with conspicuous spines; 

 cribriform organs one to eleven, 

 d'. With a conical apical elongation; abactinal membrane with simple spiniferous spicules; 

 actinal intermediate plates not imbricated; ainbulacral furrows wide and exposed; rays 

 more or less turned back; cribriform organs one to three. 

 «'. Component structure of cribriform organs lamelliform. 



/' . One cribriform organ Porcellanaster o W. Thomson. 



f. Three cribriform organs Eremicaster Fisher, p. 23. 



e^. Component structure of cribriform organs papilliform; one cribriform organ. 



Sidonaster Koehler. 



(P. No conical apical elongation of abactinal integument, but a slight peak may be present; 



abactinal membrane with pseudopaxillae; actinal intermediate plates imbricated and 



arranged in columns; ambulacral furrows narrow and concealed; rays not revertible; 



cribriform organs five to eleven (three in one case only); component structure papilliform. 



e'. Superomarginal plates with robust spines forming a single series along the median line; 



marginal plates united along median line of the rays. 



/•. Spines of adambulacral armature long and needle shaped, radiating apart; cribriform 



organs three to seven in each interradius; no ventrolateral plates in ray; actinal areas 



not granulated Styraeaster Sladen. 



p. Adambulacral spinelets spatulate, united by membrane into a scoop-shaped group; 

 cribriform organs eleven; a single series of ventrolateral plates to tip of ray; actinal 



areas granulated Chunaster Ludwig. 



«'. No spines on superomarginal plates; spines of adambulacral armature short, compressed, 



forming independent series or fans Eyphalaster Sladen. 



c*. Actinal intermediate areas covered with spiniform granules. Adambulacral plates with papilli- 

 form spinelets on the outer portion of plates; terminal plate very small and inconspicuous, 



unarmed ; cribriform organs fourteen Thoracaster b Sladen. 



6'. Inferomarginal plates aborted; one cribriform organ Albatrossaster Ludwig. 



a'. Actinal fasicioles or fimbriated channels present; cribriform organs of a simple nature and between 

 all the marginals; small superambulacral plates (in Ctenodiscus). 

 6'. An unpaired superomarginal and inferomarginal in each interbrachial arc and a corresponding 



unpaired double .series of actinal intermediate plates Pectinidiscus Ludwig. 



6'. No odd interradial marginal; no unpaired double series of actinal intermediate plates corresponding 

 thereto Ctenodiscus Miiller and Troschel, p. 31. 



Subfamily PORCKLI.AN-A.STERIN".3E Sladen. 1S83. 



Porcellanasteridfe with cribriform organs highly developed, localized. Actinal 

 interradial areas with squamiform plates covered with a simple membrane, and not 

 traversed by fimbriated channels; no superambulacral plates. 



Genus EREMICASTER (Fisher.) 



Eremicaster (subgenus of Porcellanaster) Fisher, Bull. Bur. Fisheries for 1904, vol. 24, June 10, 



1905, p. 293. TjTJe, P. tenebrarius Fisher. 

 Eremicaster Ludwig, Zool. Anz., vol. 31, 1907, p. 317. Type, P. crassus Sladen. — Fisher, Zool. 



Anz., vol. 32, 1907, p. 14. 



o Includes Caulaster Perrier; see Ludwig, Zool. Anz., vol. 31, 1907, p. 318, footnote. 

 i> Includes Pscudaster Perrier; see Ludwig, Zool. Anz., vol. 31, 1907, p. 313, footnote. 



