248 ABT. 2. — H. MATSÜMOTO : 



c— Disk flat ; oral papillse soldered together ; arms consisting of long, 

 knobby joints ; dorsal arm plates rudimentary or absent, ventral arm 

 plates very small, both being widely separated from one another; 

 tentacle pores limited to several basal arm joints, very small; those 

 beyond the second oral pores with a single tentacle scale or without 

 any , Aspidophiura. 



cc— Disk convex ; oral papillae not soldered together ; arms consisting 

 of short, stout joints; dorsal and ventral arm plates not very rudi- 

 mentary, both being in contact with one anotlier at least in several 

 basal arm joints ; tentacle pores present nearly throughout the entire 



length of the arms, large, with rather numerous scales 



AmpMopMura, pars. 



hh — Disk, as well as interbrachial ventral surfaces, covered with numerous 



plates or scales ; 

 d — Axms not very short, not very high but cylindrical, gradually 

 tapered outwards, with blunt extremity ; a few, or sometimes 

 numerous, arm spines, arranged in a single row, well spaced .... 

 AmpMopMura, pars. 



dd — Ai-ms very short, very high, higher than wide, very stout at the 

 base, rapidly tapered outwards, with very acute extremity ; numerous 



arm spines, very often dimorphic and arranged in two rows 



• , . . StegopMura. 



aa — Disk low and flat, covered with rather thin and deHcate plates or 

 scales ; arms low, being much lower than wide, or cylindrical, being 

 nearly as wide as high, covered with not very thick arm plates ; 

 ventral arm plates small, much wider than long, usually separated 

 from one another even in the arm bases ; tentacle pores, except the 



innermost one or two, very small, with only a few scales 



HomalopMura & OpMura restr.^^ 



1) Claek, 1915, has established Homalophiura, removing a number of species from OpJiiura 

 AS diagnosed in my preliminary paper. The two genera may be distinguished as follows. 



a' — Disk scales rather few and coarse, the primaries being stout and conspicuous; second oral 

 tentacle pores opening entirely outside the oral sUts ; tentacle pores comaned to two or 



