JAPANESE ASTEROIDEA. 451 



Oreaster dœderleini, n sp. 



(PL XVI, figs. 244-251.) 



This species is closely similar to 0. magnificus in general 

 form and appearance, but is distinguished from it by a slightly 

 better development of the spines on the abactinal side, the presence 

 of teat-like spines on some of the inferomarginal plates, the larger 

 number of spines in the inner row of adambulacral armature, and the 

 presence of three forms of pedicellariae on the abactinal side, two 

 of which are totally different from any found in 0. magnificus. 



The body is depressed, flat below and very slightly convex 

 above. The cross-section of the arms is nearly semicircular in 

 outline, and the arm-tips are upturned, as in most other species 

 of the genus. The interbrachial arcs are entirely open. I have 

 only one dried specimen in a tolerable condition, with r=: 73 mm., 

 E = 157mm., giving the radial ratio 2.15. 



Superomarginals. — There are 20-22 of these, and they are 

 comparatively inconspicuous in surface view, although of tolerable 

 size ; they can just or hardly be seen from the abactinal side, 

 except near the tip of the arms, where they appear on this side 

 owing to the upturning of the tips. In the interbrachial arcs the 

 plates are more or less rounded -polygonal, and the external - sur- 

 face is nearly plane ; along the sides of the arms the plates are 

 more or less rectangular or pentagonal in outline and the external 

 surface is lightly convex. The plates are entirely covered over 

 with fine granules, and each plate bears some valvate pedicel- 

 larige, which are but slightly elongated transversely or may some- 

 times be nearly round ; there may be as many as ten or a dozen 

 of them on a single plate, but the last four or five plates at the 

 tip of the arms are usually entirely destitute of them. 



