MONOGBAPH OF JAPANESE OPHIUROIDEA. 337 



If these differences between the Korean form and the typical 

 0. dubia really exist, then it is almost certain that the former is 

 not referable to the same species. Therefore, I am inclined 

 provisionally to look upon the former as a distinct species. 



Ophiocrasis Claek. 1911. 



Aside from the presence of the secondary supplementary 

 dorsal arm plates, this genus seems to me to be distinguished 

 from Ophionereis principally by negative characters and the diflerent 

 degree of development of certain common structures. The disk 

 scales are even and exceedingly fine ; no trace of the marginal 

 row of special disk scales ; no genital papillse ; arms much nar- 

 rower than in Ophionereis. Schizogonic reproduction may not be 

 a generic character. 



Key to species of Ophiocrasis» 



A — Kadial shields not very small ; ventral arm plates longer than wide 

 throughout ; smaller individuals sis-armed, reproducing by schizo- 

 gony diciydisca. 



AA — Radial shields exceedingly small and insignificant ; ventral arm 

 plates wider than long, at least in the basal parts of the arms ; 

 five-armed, not reproducing by schizogony marhtanneri . 



Ophiocrasis dictydisca Claek. 



Ophiocrasis dictydisca : Claek, Bull. U. S. Nat. Mus., LXXV, 1911, p. 

 175, fig. 79. 



Off Suno Saki, Sagami Sea ; 52-73 fathoms (Claek). Korea 

 Strait ; 59 fathoms (Claek). 



