MONOGEAPH OF JAPANESE OPHIUBOIDEA. 247 



This genus is formed by a single species, Ophiofona gymnopora 

 Clakk, 1909. 



Revision of Ophiura Lamarck, 18] 6 ( = Ophioglypha Lyman, 1865). 



As Ophiura s. ext. is a very large and diffuse genus, the 

 necessity for subdivision is admitted by many authors. Ludwig 

 proposed to divide it into two genera according to the presence 

 or absence of the arm combs. But his type of Ophioglyphina is, 

 in my opinion, merely a typical Ophiura. Kœhler tried to 

 divide this genus into two sections according as the second oral 

 tentacle pores opened more or less within the oral slits or entirely 

 outside it. In my opinion, the position of the pores in question 

 is not of such value, though it is of some importance in making 

 subdivisions of Ophiura s. ext. I cannot agree with those authors 

 who try to subdivide this genus by only one or two characters ; 

 all characters should be taken into account. From this point of 

 view, I have come to the conclusion that Lyman's subdivisions 

 may be accepted in principle. I propose here to divide Ophiura, 

 as liitherto understood, into a number of genera, which may be 

 distinguished as follows. 



A — Adorai shields not oval but long ; no supplementary plates among 

 the oral plates and adorai shields ; genital papillse always, and arm 

 combs usually, present. 

 a — Disk high, covered with very stout plates or very thick scales ; 

 arms higher than, or as high as, wide, also covered Avith very 

 thick, heavy arm plates. 



• h — Disk covered chiefly or only with very stout primaries and radial 

 shields ; interbrachial ventral surfaces almost entirely occupied by a 

 very stout central plate, besides the very heavy genital scales. 



