REPORT ON THE ASTEROIDEA. 



495 



a. Rays broad. Aperture-papillae simple. 



1. Interbrachial arcs indented, defining broad lanceo- 



late rays. Spiracula numerous, large and con- 

 spicuous. Spinelet-tips very prominent . . viearius, 



2. Interbrachial arcs not indented; form pentagonoid. 



Spiracula few, small and inconspicuous. Spinelet- 

 tips not prominent ...... ■pellucidus. 



/3. Rays attenuate. Apcrture-papilke conib-like" . . . in/emalis. 

 (J. AdambulacraJ armature consisting of three spinelets. 



a. Muscular fibrous bands close, subdiffused, coherently reticulated. 



a. Paxillre-crowns forming definite areas in relief. 



a. Paxillar elevations closely crowded. Spiracula uniformly 



distributed, not in lines ...... cxlat)i<. 



fi. Paxillar elevations widely spaced. Spiracula confined to 



interspaces, arranged in lines ..... cruci/er. 



b. Paxillae-crowns not forming definite elevated areas. 



a. Spines of the adambulacral armature partially webbed. 



Three pairs of secondary mouth-spines . . . anomalies, 



fi. Spines of the adambulacral armature not webbed. Two 



pairs of secondary mouth-spines. 



1. Meshes of supradorsal membrane irregular and not 



uniform. Spines of the adambulacral armature 



unequal ........ latebrosus. 



2. Meshes of supradorsal membrane small and uniform. 



Spines of the adambulacral armature equal . porosissimus. 



b. Muscular fibrous bands fine, definite, widely spaced, simply intercrossing. 



a. Supradorsal membrane with granular bodies ..... graniferus. 



b. Supradorsal membrane devoid of granular bodies. 



a. Spines of the adambulacral armature long and needle-shaped geometricus. 

 fi. Spines of the adambulacral armature short and compressed. 



1. Muscular fibres very numerous in supradorsal mem- 



brane. Webof theactinalfloorwithcrossmuscular 



fibres. Longest actino-lateral spine the 12th . puUatus. 



2. Muscular fibres not very numerous in supradorsal 



membrane. No muscular fibres in the web of the 

 actinal floor. Longest actino-lateral spine the 17th membranaceus. 

 D. Adambulacral armature consisting of more than three spinelets. 



a. Three or four spinelets in the adambulacral armature. Aperture-papillae 



five to seven rayed, comb-like, large. One pair of secondary mouth-spines coccinatus. 



b. Three to five spinelets in the adambulacral armature. Aperture-papillae 



simple, small and dumpy. Two or three pairs of secondary mouth-spines . prxcoquis. 



1. Hymenaster nobilis, Wyville Thomson (PL LXXXVII. figs. 1-3). 



Hymenaster nobilis, Wyville Thomson, 1876, Journ. Linn. Soc. Lond. (Zook), vol. xiii. p. 73, fig. 11 : 

 Voy. of Challenger, Atlantic, vol ii. p. 238, fig. 48. 



Marginal contour pentagonal, interbrachial arcs very slightly indented, the margii 

 forming a continuous curve of small degree from tip to tip. Rays not produced, and 

 tapering very slightly beyond the natural angle of a pentagon. The minor radius is in 



