ÎIONOGEAI'H OF JAPANESE OPHIUKOIDEA. 197 



long ; distal oral papilla not much larger tlian the apical papilla 

 and tentacle scales, rather thick ; dorsal arm plates very convex in 



longitudinal secticm ; ventral arm plates not keeled iris. 



II — Five flattened arm spines, of which tlie maximum length is about 

 thrice the corresponding arin joint ; disk scales distinctly imbricated ; 

 radial shields not xevy long, pear-seed shaped ; oral shields small, 

 nearly as long as wide ; distal oral papilla much larger than the 

 apical papilla and tentacle scales, very flat and thin ; dorsal arm 

 plates rather straight in longitudinal section ; ventral arm plates 



with a median keel iridoiths. 



Jck — Six or seven arm spines. 



m— Six arm spines, of which the third or fourth from above is the 

 longest; radial shields long and narrow; oral shields diamond - 

 shaped, about as long as wide ; distal oral papilla subspinous, 

 long, compressed li'dkeui. 



mm— Six or seven arm spines, of which the lowest one is the longest; 

 radial shields extremely small, short and narrow ; oral shields oval, 

 about as long as wide; distal papilla very large, fan-shaped, flat., 

 micraspis. 



AA — Tentacle scales absent ; disk mostly naked, the disk scales persist- 

 ing only around the radial shields ; numerous arm spines, of which 

 the lower ones are rough at the tip. 



n — rive to seven arm spines ; dorsal and ventral arm plates wider 

 than long. 



o — Five arm spines near disk, but four more distally ; dorsal arm 

 plates very large and wide even at the arm bases; arms twelve or 



thirteen times as long as the disk diameter œstuarii. 



00— Six or seven arm spines near disk, but five or six more distally; 

 dorsal arm plates very small and rudimentary at the arm bases ; 

 arms exceedingly long, more than thirty times as long as the disk 

 diamete]- vadicdla. 



?2?i — Ten arm spines; dorsal and ventral arm plates much less wide than 



