244 AET. 2. — H. MATSUMOTO : 



the pentagonal body. The first one is very large, hastate, but 

 with mnch ronnded apex, lateral edges strongly concave corres- 

 ponding to the second oral tentacle pore, and with an indentation 

 at the outer edge, longer than wide, very wide without. Follow- 

 ing plates, which become smaller outwards, quadrangular, with 

 strongly concave lateral edges corresponding to the tentacle pore, 

 with a saddle- shaped surface. They are closely apposed to one 

 another, except the last one or two, which are very rudimentary, 

 rhomboidal and isolated. The tentacles are very large, uniformly 

 diminisliing in size and lying closer together as they proceed 

 outwards, and arranged in a pentamerous petaloid series as a whole. 

 The first pair of tentacles in ventral view are homologous with 

 the second oral tentacles of other ophiurans, because they are 

 situated between the first ventral arm plate and the adorai shields 

 and belong morphologically to the same arm, joint with the latter. 

 They are much larger than the other tentacles. The second pair 

 are the true first arm tentacles. They belong to the same joint 

 with the second ventral and the first dorsal and lateral plates. 

 Each tentacle pore is provided with one or two scales, which are 

 rather small, lanceolate, covered by skin, their concave surface 

 facing the tentacle pore, often turned up. The outermost and 

 smallest tentacle pores have no scale. Each two successive tentacle 

 pores are separated by a ridge of the basal or adradial part of 

 the lateral arm plate, which belongs to the same joint with tlie outer 

 of the two pores. 



The free distal portion of the arms outside the pentagonal 

 body is very abortive, exceedingly slender, uniformly tapered out- 

 wards, entirely covered by the lateral plates and easy to break. 

 There is a single, exceedingly small and acute arm spine on each 

 lateral plate ; but in the first one or two free joints, there are 



