240 BULLETIN 100, UNITED STATES NATIONAL MUSEUM, 



Subfamily GONIASTERINAE Verrill/ 1899 (extended). 



Genus ROSASTER Perrier. 



Rosaster Perrier, 1894, p. 386. T.vpe, PcntayonaHier (tlcxandri Perrier.- - 

 Fisher, 1911, p. 164 ; 1913cr, p. 629. 



Ncreidaster Verrill, 1899, p. 186. Type, Nympha^ter sym^boUcus Sladen. 

 [Not Ncreidaster, Fisher, 1911(Z, p. 170, which as used here is synony- 

 mous with Ccramastcr. I had not then seen the type of the genus 

 which lias not the anatomical characters given in the key.] 



Diagnosis. — Goniasteridae resembling Mediaster in having internal 

 supplementary 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 

 difi'ering in the serial arrangement of gonads, in having strongly 

 tabulate subpaxilliform abactinal plates, and in lacking the strongly 

 angular furrow margin to the adambulacral plates. Form stellate, 

 with well-developed raj^s ; superomarginals in contact distally, some- 

 times for a considerable portion of ray; abactinal plates strongly 

 tabulate on papular areas and with internal radiating connecting 

 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 slen- 

 der, 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. 



Remarks. — The three species which I have placed here under the 

 genus Rosaster agree in having the characters mentioned in the 

 diagnosis above, and in these respects differ from Nymphaster., 

 Mediaster, and C eramaster, the most nearly related genera. 



I have long suspected that Rosaster alexandri might be allied to 

 the section of Nymphaster called Nereidaster by Verrill in 1899. But 



1 See Fisher, 1911rf, pp. 160, 161, 196. The subfamily is used here in the same sense. 

 Verrill (1914a, p. 294) believes that Mediaster should be placed in the subfamily 

 Mcdiasterinae on the basis of the existence of radiating internal ossiclos connecting the 

 bases of the abactinal plates. Roxaster would probably be placed in the same subfamily, 

 although differing in lacking superambulacral ossicles. Mediaster and Ceramaster are 

 difficult to separate on external characters, and can be easily confused unless they are 

 dissected. It seems rather unnecessary to place in separate subfamilies two genera 

 which can bo distinguished only by an expert. Some of the species of Rosaster have 

 up to now been included in "Nymphaster, and in " 'Nereidaster," both supposedly typical 

 Goniasterinae. 



