2Y0 BULLETIN 'S, UNITED STATES NATIONAL MUSEUM. 



«'. Adambulacral armature in longitudinal series parallel to furrow; furrow spines numerous; 

 actinal interradial areas small, and postadambulacral plates with fascicles; marginal 



plates without conspicuous channels between Aphroditaster Sladen. 



e'. Adambulacral armature a compact group of similar spines in more or less evident trans- 

 verse series; furrow spines two or three; actinal interradial areas large with numerous 

 imbricating plates covered with coordinated compact groups of numerous short spine- 

 lets, leaving narrow interradial channels; marginal plates with conspicuous inter- 

 vening channels Gephyrewiler Fisher, p. 175. 



c*. No unpaired median tooth to each pair of mouth plates; pedicellarise when present low 

 bivalved, or higher with two or more spatulate jaws; superambulacral plates rudimentary 

 or absent. 

 d'. Abactinal plates connected by independent internal slender regular radiating ossicles over 

 the papular area; rudimentary superambulacral plates present, 

 e". Abactinal plates medium-sized or small, roundish, not developed into very large cylindrical 

 tabula; marginal plates conspicuous; bivalved or two-jawed spatulate pedicellarise; 

 adambulacral spineleta more or less prismatic in longitudinal series, numerous; no 

 intermarginal papulae; no internal supplementary actinal intermediate plates. 



Mediaster Stimpson, p. 196, 

 e'. Abactinal plates lobed, very large with large cylindrical tabula bearing coordinated gran- 

 ules; marginal plates comparatively small; pedicellarise when present with two to 

 fix slender upright jaws; supplementary internal actinal intermediate plates in neigh- 

 borhood of the ambulacrals; intermarginal papulae Nectria Gray. 



d^. Abactinal plates without internal slender radiating connecting ossicles; the plates of the 

 papular areas slightly to conspicuously lobed. No superambulacral ossicles. 

 e'. General form stellate frequently with long rays, a single series of abactinal plates reaching 

 the tip of ray, or the few distal superomarginals in contact medially; pedicellarise 



high and spatulate Nereidastcr Verrill. 



e*. General form pentagonal, never with long rays; two or three superomarginals sometimes 

 in contact medially; pedicellaria;, if present, small bivalved, or with two or three 



spatulate jaws, but not high and spatulate Ceramaster Verrill, p. 204. 



a'. Superomarginal plates contiguous throughout most of ray, the more or less tabulate abactinal 

 plates being confined to disk; slender spatulate pedicellarise. 

 6'. Abactinal plates only .slightly tabulate, granulate. No enlarged actinal adambulacral spines; 

 furrow spinelets not very regular nor spaced from actinal; pedicellarise all small; no rudi- 

 mentary superambulacral plates Xymphasler Sladen. 



6'. Abactinal plates of radial areas strongly tabulate, covered with short spinelets rather than 

 granules; furrow spinelets long, regular, and spaced from actinal; one or two enlarged actinal 

 adambulacral spines; a few comparatively large slender spatulate actinal pedicellarise; 



rudimentarj' superambulacral plates Rosaslcr Perrier. 



II. -Vbactinal plates only exceptionally tabulate (Ceramaster); usually flat or convex, roundish, poly- 

 gonal, or stellate; smooth, granulous or spiny; in mosaic, with or without secondar)- intermediate 

 plates which do not form, with the primaries, a close reticulated skeleton. 

 a'. Body not covered by a smooth or granulous membrane, nearly or quite obscuring the abactinal 

 plates. 

 b'. Abactinal plates with upright spines or tubercles of conspicuous size, but no low bivalved pedi- 

 cellariie; pedicellarise, when present, spatulate or like miniature sugar tongs; more than a 

 pentagon of five tubercles on disk. 

 c'. No large sharp or blunt actinal intermediate or adambulacral spines; armature of adambula- 

 cral plates graduated into actinal granulation Goniaster Agassiz. 



c*. Adamliulacral plates with one or more conspicuous sharp or blunt movable or rigid spines on 

 their actinal surface; adambulacral armature not graduated. 

 (f. Small granulated plates and granules between primarj' abactinal plates, each of which 

 bears a large smooth conical tubercular spine; actinal intermediate plates each with a con- 

 spicuous upright blunt spine; scattered intermarginal plates AmpJnastcr Verrill. 



