168 AKT. 2, — H. MATSUMOTO : 



less perfectly closed ; an additional papilla present just outside and 

 above the infradental one. 

 a — Disk entirely free of spines. 

 h — Outermost oral papilla small and not operculiform ; radial shields 



divergent AmpJiioplus. 



hh — Outermost oral papilla very large and operculiform ; radial shields 



more or less perfectly joined Ampldddlus. 



aa — Disk beset with scattered spines, 

 c — Oral papillie close-set, the outermost one being not very long and 

 spiniform but short and flat ; radial shields divergent ; three to five 



arm spines ; tentacle scales short, flat, leaf-hke AmpJdacantha. 



cc — Oral papillae well spaced and conical, the outermost one being very 

 long and spiniform ; radial shields perfectly joined ; six to ten arm 

 spines ; two spiniform tentacle scales, of which the adradial one is 



very long and slender Ampldlimna. 



II — AmpJdodla-group : — Oral papillae +1+11—111, three or four on 



either side, subequal, forming a continuous row, so that the oral 



slits are more or less perfectly closed ; no additional papilla just 



outside and above the infradental one. 



d — Disk free of spines and granules. 



e — Disk soft, witliout special marginal scales or spines ; radial shields 



usually divergent Amphiodia. 



€6 — Disk solid, with a row of special marginal scales or spines, so that 

 the boundary between the dorsal and ventral sides of the disk is 



very sharp ; radial shields perfectly joined Ophiophragmus. 



dd — Disk with numerous scattered spines or granules Ophiocmda. 



Ill — AmpTdpholis-gYoxi]):—Ova\ pa pillas +1 +11 —III, three on either 

 side, the outermost one being very large and operculiform ; oral slits 

 perfectly closed ; no additional papilla just outside and above the 

 infradental one. 



f — Disk entirely free of spines AmpMpholis. 



ff — Disk with scattered spines or granules Opidostigma. 



IV — Ampldnra-gvon-p : — Oral papillae +1—11 +111 or sometimes +1 



