JAPANESE ASTEROmEA. 



427 



central plate and five radial plates surrounding it on all sides and 

 forming the apices of the groups of radial plates just mentioned. 

 In the same radial line with these five apical plates, one can 

 usually make out a series of somewhat regularly square plates 

 running through the whole or at least the greater part of the length 

 of the arms. In the basal part of the arms there is one more series 

 on either side of this radial series which terminates towards the 

 centre just before reaching the apical plates. Between this last 

 mentioned series, the superomarginals and the larger interradial 

 plates above mentioned lie a number of small plates of irregular 

 form. The abactinal plates extend mostly to the tip of the 

 arms, and only the last one or two pairs of superomarginal plates 

 are in contact with each other. 



The abactinal plates are all uniformly covered with fine 

 granules exactly similar to those of the marginal plates. The 

 majority of them bear pedicellariae similar in form to those of the 

 superomarginals, but usually so small as to be entirely inconspi- 

 cuous (PL XIII, fig. 215). 



The tubercles on the abactinal surface mentioned by several 

 writers as a characteristic of this species are variable in number and 

 position. In what may be looked upon as a typical case, there are 

 five tubercles in all, one for each radius, and all equidistant 

 from the centre of the disk. In one or two of the specimens 

 the tubercles have been abraded, but their position and number can 

 be told, as they leave hollow traces behind. In one specimen there 

 are only three of these tubercles, while in another there are as many 

 as twenty. In the latter case five of the larger tubercles are situat- 

 ed as in the typical case and the remainder lie mostly within the 

 pentagon formed by the former and only one outside it. In a 



