JAPANESE ASTEEOIDEA. 105 



the superomarginals, while those that lie on the actinal side of 

 the same spine are like those oE the ventrolateral plates, being 

 shorter, flattened and rounded at the top. On the plate lying next the 

 interradial line there are in a specimen of K=:20 mm. some fifteen 

 of these spinelets on either side, of which four or five lie between the 

 abactinal end of the plate and the actinolateral spine. The delicate 

 skin folds that cover the lateral faces of the superomarginal plates 

 are continued downwards on to the inferomarginals to the level of 

 the actinolateral spine. The external surface of the inferomarginal 

 plates is usually more or less finely granulated. 



Adambulacrals. — Of these there are for each side of an arm 

 one to three or four more than the inferomarginals. The first 

 two plates appear always to correspond to the first marginal 

 plate, being connected with the latter by the series of ventro- 

 lateral plates lying between them. As to the remaining ad- 

 ambulacral plates each one may correspond to a marginal plate or 

 some may be intercalary in position. The adambulacral plates stand 

 out very distinctly on treatment with caustic potash and are then 

 seen to present each a rounded border towards the ambulacral 

 furrow. On this border there is a row of three to five, short, 

 sharply pointed spines, of which the one at the adcentral end is 

 usually the largest on the first three or four plates, while on the 

 remaining plates these spines are more nearly equal and spread out 

 in the form of a fan. There may be one or more additional small 

 spines on the actinal surface of the plate, usually close to the 

 adcentral or abcentral border (PI. VII, fig. 115 ; PI. VIII, fig, 122). 



Mouth-plates. — The mouth-plates are relatively large and 

 conspicuous and the pair taken together is almost regularly el- 

 liptical or rhomboidal in outline. On each plate there is at the 



