JAPANESE ASTEEOIDEA. 107 



were only six. These plates are imbricated like the scales of a 

 teleost and bear on their outer border, i. e. the border facing the 

 transverse furrow dividing a group from the next, delicate flattened 

 spines, two to fi.ve for each plate, which sometimes become 

 apparent only after treatment with caustic potash. 



Paxillœ. — The paxillse may be well spaced or closely set 

 according as the dorsal membrane of the animal is convex or 

 flat, and this depends again upon the amount of mud contained 

 in the stomach. In some specimens the paxillaa are so closely 

 pressed against one another as to impart a comparatively smooth 

 appearance to the abactinal surface. The paxillse are all very 

 small but especially so are those that are found on the central 

 conical prominence. There is no distinction between the central 

 and peripheral coronal spinelets except in their positions, and in 

 larger paxillao there may be as many as eight peripherals and 

 one or two centrals, while in smaller ones the centrals are usual- 

 ly absent and the peripherals may be only three or four in 

 number. The tabulum is comparatively short and has an expand- 

 ed base of rounded outline when viewed from the interior of the 

 body and remains entirely separate from the neighbouring ones (PL 

 VII, fig. 116, 117 ; PL VIII, fig. 124). The papulae are distribut- 

 ed singly between the paxillae, mostly one between any three 

 contiguous paxillEe. They are however absent in the narrow band- 

 shaped areas along the crest of the arms and the interradial 

 lines. The central conical prominence and its immediate vicinity 

 are also destitute of papulae. 



Madreporite. — The madreporite shows on the surface, although 

 the peripheral parts may be slightly covered over by the sur- 

 rounding paxillse, and may be from t^Yice to four times as far 



