546 



a. Inferomarginal plates with a tuft of enlarged spines at 



outer end or a series along aboral margin; border of 

 rays subserrate; papulae distributed all over abactinal 

 surface; madreporic plate very large bearing many 

 paxillae on its surface. 



b. Paxillae conspicuously large in central portion of disk 



and along median area of rays, their spinelets descending 

 the pedicel in bristling array, so that they resemble 

 miniature bottle-brushes ; rays broad near tips; abactinal 

 plates strongly stellate along median radial area, with 2 

 or 3 papulae to each area instead of 1 ; actinal inter- 

 mediate areas broad, far along ray . . . . D. eximius Fisher. 

 bb. Paxillae not conspicuously larger in central portion of 

 disk, etc., their spinelets grouped at top of pedicel; rays 

 evenly tapered to tip; abactinal plates along median 

 radial area either round or stellate but not surrounded 

 by many papulae, never by more than 8; actinal inter- 

 mediate areas narrow beyond middle of ray. 



c. Abactinal plates lobed; marginals broader, covered with 



compact, rigid, polygonal granules (superomarginals) 

 and squamae (inferomarginals); superomarginals with 1 

 or 2 tubercles; adambulacral furrow spines compressed 

 with broad side to furrow , actinal intermediate plates 

 covered with squamiform spinelets . . D. borealis, new species. 



cc. Abactinal plates not lobed; marginals narrower, the 

 superomarginals without tubercles and covered with 

 delicate capillary spinelets; inferomarginals with deli- 

 cate, imbricating, narrow, squamiform spinelets; adam- 

 bulacral furrow spines strongly compressed with edge 

 to furrow; actinal intermediate plates with slender 

 spinelets D. laetuiophilus new species. 



aa. Inferomarginals entirely without specialized spines; 

 border of ray even, not serrate from the form of infero- 

 marginals; papulae absent from center of disk; madre- 

 poric body median sized, hidden, but with only 1 or 

 2 paxillae on its surface D. anoplus new species. 



Dtpsacaster borealis new species. 



Related to D. eximius Fisher but differing in the shape of rays, in 

 having smaller paxillae with fewer spinelets and these not descending 

 far down the pedicel; in not having the paxillae conspicuously enlarged 

 on center of disk and along middle of ray ; in the shape and position of 



