MONOGRAPH OF JAPANESE OPHIUROIDEA. 269 



d. — Disk scales coarse ; comb pax>illa3 vei'j loDg and slender, eight to 



ten of them being visible from above Idnhe^-gi. 



dd. — Disk scales fine ; comb papillae very short, twelve to fourteen of 



them being visible from above sars'ir 



CO.— Disk scales more or less obscured by a thick, soft 'skin ; lower arm 



spines of basal arm joints spatulate ßagellata. 



hb. — Four arm spines ; oral shields wider without than within ; comb 



papillae short qiiadrisplna. 



aa. — Ai'm combs rudimentary or entirely wanting, genital papillœ 

 present. 

 €. — Three exceedingly long arm spines ; dorsal arm plates oval, longer 

 than wide ; disk scales fine ; oral shields Avider without than within 



, oöplax. 



ce. — Four arm spines, not exceedingly long ; dorsal arm plates more or 

 less quadrangular, much wider than long ; disk scales coarse ; oral 



shields wider within than without maculata. 



BB. — Arms cylindrical, about as wide as high "at the free base; three 



arm spines, minute, peg-like, short, well spaced 



imbeciUis-grouT^ (II). 



/. — Disk scales coarse ; radial shields joiued in pairs ; oral shields 

 trefoil-shaped, about as long as wide ; arm bases within the disk 

 especially wide ; first ventral arm plate very large and rhomboidal ; 



dorsal arm plates separated from one another imbecillis. 



ff. — Disk scales fine ; radial shields nearly or entirely separated from 

 one another ; oral shields not trefoil-shaped ; arm bases within 

 the disk not especially wide ; first ventral arm plates small ; dorsal 

 arm plates meeting with one another. 



g. — Radial shields short, only slightly longer than wide ; oral shields 

 pentagonal, wider than long ; uppermost or lowest arm spine longest, 

 middle one shortest, none of them coming up to the length of the 



corresponding arm joint micracantha. 



gg. — Badial shields long, about twice as long as wide ; oral shields pear- 

 shaped, much longer than wide; uppermost arm spine longest, 



