STARFISHES OF THE PHILIPPINE SEAS. 243 



&. Rudimentary snperambnlacral plates present; several series of abactinal 

 plates extending to near end of ray, and normally one or more series 



reaching the terminal plate Mediaster. 



c■^ No rudimentary superambiilacral plates ; distal superomarginals usually 

 in contact, forming a slender, pointed ray, or if not in contact, sepa- 

 rated for a considerable distance only by a single series of reduced 



abactinal plates Rosaster. 



a". Without internal radiating ossicles connecting the abactinal plates ; gonads 

 always interradial in position. 

 h^. General form pentagonal or stellato-pentagonal with vei-y short rays; 

 abactinal plates of papular areas tabulate ; superomarginal plates not 

 contiguous on the rays, one or more series of abactinal plates reach- 

 ing the terminal plate (occasionally a few distal plates in contact 

 medially) ; adambulacral plates with a straight or curved furrow margin 

 and with a series of subambulacral spines spaced from the furrow 

 spines, but no strongly angular furrow margin separating consecutive 



pairs of tube-feet Ccramaster. 



h'. General form stellate with long slender rays ; abactinal plates granulate 

 but not tabulate, although sometimes a trifle raised ; superomarginals 

 contiguous throughout the long slender rays ; adambulacral plates with 

 (at least distally) a strongly angular furrow margin, and angular fur- 

 row series, separating consecutive tube-feet ; no regular comb of 

 subambulacral spines spaced from furrow series (although sometimes 

 the inner subambulacrals are enlarged) Nymphastcr. 



It will be seen from this table that Nymphastcr is rather sharply 

 set off from Rosaster by the low abactinal plates lacking internal 

 supplementary ossicles, by the strictly interradial gonads (1 tuft), 

 and by the characteristic form of the adambulacral plates and arma- 

 ture. The principal likeness between the two groups is in the long, 

 slender rays and contiguous superomarginals. 



KEY TO THE KNOWN SPECIES OF ROSASTER. 



a'. Superomarginals contiguous for nearly half to more than half of R; not 

 separated by a single series of small plates for a considerable distance. 

 h^. Furrow spines 4 or 5, at least few in number ; size small, 

 c^. Abactinal paxilliform plates roundish, with subequal, thorny spinelets ; 

 granules of marginal plates longer than diameter, thorny and re- 

 sembling very short spinelets ; furrow spiues relatively long, slender, 



compressed alexandri. 



c'. Abactinal plates hexagonal, witli xniequal granules, the peripheral on the 

 lateral edges of the radial and adradial plates being enlarged and 

 opercular, covering the papulae beneath ; granules of marginal plates 

 small, depressed, hemispherical, broader than high; furrow spines 



short nanniis, p. 244. 



?A Furrow spines 7 or 8 to 14 or 15 ; size small to large. 



c\ Size small ; radial tabulate plates roundish, a few distal abactinal plates 

 isolated singly between consecutive pairs of contiguous superomar- 

 ginals ; furrow spines 7 or 8; subambulacral spines and granules in 



3 series confinis. 



c*. Size medium or large ; radial tabulate plates hexagonal. 



d\ Furrow spines 14 or 15; large radial plates with 12 to 23 central 

 granules mimicvs, p. 250. 



