SEA LILIES, STARFISHES, ETC. — CLARK. 



39 



Genus Mediaster, Stimpson. 



Mediaster atjstr alien sis, 1 sp. nov. 



(Plate ix., fig. 1-2; Fig. 1-3.) 



R=82 mm.; r=30 mm.; R=2.67r. Br=30 mm.; 

 R=2.67 br. Br at middle of ray=ll mm. ; at tip, 2.3 mm. 

 In the largest specimen, R=100 and r=40 mm. Disk large 

 and flat ; arms wide at base but tapering rapidly to a nearly 

 cylindrical tip. Abactinal plates tabulate, more or less paxilli- 

 form (Fig. 1) especially at centre of disk and along midradial 



Fig. l.xlO. Fig. 2.xl0. 



Fig. 3.xlO. 



lines ; small and numerous ; the largest and most paxilli- 

 form are crowned with a marginal series of 12-15 angular, 

 blunt spinelets or coarse granules and within this circle 

 3-8 similar but smaller granules ; the smallest and least 

 paxilliform plates adjoin the superomarginals in the 

 interradial areas and are crowned with a little group 

 of 3-5 angular granules ; the coarseness or fineness 

 of the paxillar granules shows great diversity in different 

 individuals and even in different parts of the same disk ; thus 

 in one specimen, plates proximal to the madreporite carry 

 10-20 coarse, well-spaced granules, while plates of the same 

 size, distal to the madreporite, carry 25-40 smaller, more 

 rounded and more crowded granules. Occasionally one or 

 more of the granules is replaced by a 2-jawed pedicellaria ; in 

 the holotype, these pedicellarise are very numerous and are so 

 much higher than the granules (about twice as high), that they 

 are quite conspicuous ; they are also quite symmetrical and 

 frequently entirely replace the granules on the top of the 

 plate (Fig. 2) ; in other specimens, pedicellariae are exceedingly 

 rare, while in still others, though common, they are small and 



1. Australia-{-ensis, expressing locality. 



