90 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



Genus CTENOPLEURA Fisher. 



Ctenoplcura Fisher, 1913a, p. COS. Type, C. astropectinides. 



Diagnosis. — Allied to Astropecten, but differing in having the 

 gonads in a crowded series parallel to the marginal plates, and 

 extending about a third the length of ray; inferomarginal plates 

 with a lateral, oblique, compact comb of 3 to 5, usually 4, slender 

 api^ressed spines, closely resembling the lateral comb of Perse- 

 phonaster, and in addition 1 to 5 flattened, appressed spines on the 

 actinal surface; adambulacral plates Avith usually 4 or 5 furrow 

 spines (or, on the second and third plates, sometimes 6 or 7) in- 

 stead of 3, the usual number in Astropecten; subambulacral spines 

 small, none enlarged ; often a fasciculate subambulacral pedicellaria 

 is present ; Polian vesicles 5. Other characters as in Astropecten. 



Remarks. — This genus includes also Astropecten ludwigi de Loriol, 

 of Japan, in which the gonads are arranged in series extending 

 about a third the length of the ray. In Astropecten the gonads form 

 a single tuft on each side of the interbrachial septum. C. ludwigi 

 is rather closely related to C. astropectinides. Both have the general 

 appearance of Astropecten^ although the armature of the marginal 

 plates is more like that of Perse phonaster. A few species of Astro- 

 pecten have 4 or 5 furrow spines proximally, but the usual number 

 is 3. Many species of Astropecten have 6 Polian vesicles, but I am 

 not certain that the character is of generic value. 



The arrangement of the gonads in series will separate Ctenopleura 

 from Leptxj chaster.^ Bathyhiaster., Psilaster., Blakiaster Astrofnesites, 

 Ctenophoraster, Persephonaster, Tritona^ter, and Patagiaster. The 

 very restricted development of the actinal intermediate plates will 

 at once distinguish it from other Astropectinidae having serially ar- 

 ranged gonads, such as Anthosticte., Tethyaster^ Thrissacanthias., 

 Dipsacaster., and Plutonaster. The armature of the marginals will 

 separate Ctenopleura from LoncJwtaster and Ripaster in which the 

 gonads are not described, while Sideriaster and Moiraster are distin- 

 guished by their large actinal interradial areas. Among the more 

 nearly related genera some further differences may be enumerated. 

 Persephonaster lacks the very angular astropectinoid adambulacral 

 plates and has an angular series of mouth spines high in the furrow, 

 while BlaMaster has pseudopaxillae and an odd interradial series 

 of actinal intermediate plates. ThriHsacanthias differs in having 

 an enlarged subambulacral spine and a less angular furrow series. 



