630 PROCEEDINGS OF THE NATIONAL MUSEUil. vol.43. 



the presence of internal abactinal ossicles, similar to those of " Nynb- 

 jjhaster" symbolicus (and of the species herein described) , leaves no 

 doubt that Nereidaster and Rosaster are the same. Rosaster sym- 

 holicus (Sladen) is represented in the collection by 2 adult specimens. 



A further discussion of the anatomy and relationships will have to 

 be deferred until the final report. MeanwliUe the following diagnosis 

 of Rosaster, drawn up wdth reference to the seven known species, may 

 be useful. 



Goniasteridse resembling Mediaster in having internal supple- 

 mentary ossicles connecting the abactinal plates and in having the 

 gonads arranged in series extending along the rays, but differing in 

 lacking rudimentary superambulacral ossicles, and in having the 

 superomarginals in contact medially over a considerable portion of 

 the ray (if separated, then only by a single series of small plates for a 

 considerable distance) ; pedicellariae always slender, tong-shaped, not 

 of the low-bivalved form. Resembling Nymphaster in form but 

 differing in the serial arrangement of gonads, in having strongly 

 tabulate subpaxilltform abactinal plates, and in lacking the strongly 

 angular furrow margin to the adambulacral plates. Form stellate, 

 with well-developed rays; superomarginals in contact distally, some- 

 times for a considerable portion of ray; abactinal plates strongly 

 tabulate on papular areas and with internal radiating comiecting 

 ossicles; actinal interradial areas large; adambulacral plates with a 

 straight or slightly curved furrow margin bearing a regular comb of 

 few to many, usually compressed, spines, and spaced from these a 

 subambulacral series of spines, more or less prismatic, the outer part 

 of the plate being occupied by granules sometimes graduated in size 

 toward the subambulacral series of spines ; pedicellariae rather slender, 

 spatulate, and intrenched; no superambulacral ossicles; gonads in 

 several independent tufts which extend in a series along the ray, 

 close to, or removed from, the margin and usually parallel to the 

 radius; tube feet without deposits. 



KEY TO THE KNOWN SPECIES OF ROSASTER. 



a^ . Superomarginals contiguous for nearly half to more than half of II ; not separated by 

 a single series of small plates for a considerable distance, 

 fc'. Furrow spines 4 or 5, at least few in number; size small. 

 c\ Abactinal paxilliform plates roundish, with subequal, thorny spinelets; gran- 

 ules of marginal plates longer than diameter, thorny and resembling very 

 short spinelets; furrow spines relatively long, slender, compressed. 



alexandri. 



c^. Abactinal plates hexagonal, with unequal 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 nannus. 



V^. Furrow spines 7 or 8 to 14 or 15; size small to large. 



