76 



AET. 2. — H. MATSUMOTO 



Total length of the arm 12G mm. 



Width of the ventral side of the arm base 



within the disk .... .... .. ' 4.5 mm. 



Disk five-lobed, with concave interbrachial borders, covered 

 by a thick skin, which is apparently smooth, but contains very 

 fine and close-set grannies of microscopic size. On the radial ribs, 

 these granules are very flattened and smooth, and coarser, being 

 visible even to the naked eye. Several smooth, hemispherical 



tubercles are scat- 

 tered on the disk. 

 Eadial ribs gently 

 raised and forming 

 rounded ridges, 

 with rather in- 

 distinct outlines, 

 not quite reaching 

 the centre ; their 

 back, is marked 

 with concentrically 

 arranged swellings, 

 corresponding to 

 the imbricating, soldered plates, of which the radial shields are 

 composed. The ventral surface of the disk appears very smooth 

 to the naked eye. Genital slits not very large. Madreporic shield 

 single, at the inner corner of one of the interbrachial ventral sur- 

 faces, small, transversely oval. The teeth and dental papillœ are 

 conical and rather stout. The oral papilla? and lower dental 

 papill99 are smaller and very short ; their number for each oral 

 angle is not very great. 



Arms slender and branched, with distinction of trunk and 



Fig. 22. Astrocladus annuluius. xl^. a. From above. 

 h. From below. 



