SEA LILIES, STARFISHES, ETC. CLARK. 33 



Family GONIASTERID^. 



Genus Mimaster, Skiden. 



]\IlMASTER GRACILIS,! Sp. nOV. 



(Plate VII., fig. 1-2.) 



R=60 mm.; r=18 mm.; R=3.3 r. Br=18 mm.; 

 11=3.3 br. Br at middle of ray, 8 mm. ; at tip, 3 mm. 

 Disk large, very flat in holotype, but much thicker and more 

 elevated in other specimens ; rays narrowing rapidly from the 

 rather broad base, at first flattened but more or less cyhndrical 

 near tip. Abactinal surface of disk and rays covered by 

 rounded or substellate plates, which, near centre of disk and 

 along the radial lines are quite closely crowded ; each plate 

 bears a paxilla crowned with 10-12 (or more) slender spinelets 

 exceeding the length of the paxilla stalk ; the appearance of 

 preserved specimens abactinally depends primarily on whether 

 these spinelets were drawn together into a cylindrical bundle 

 on each paxilla, when the starfish died, or whether they re- 

 mained more or less flaring ; the spinelets are so delicate, 

 they are frequently more or less broken. Madreporic body 

 large, about 5 mm. in diameter, fully exposed ; its distal 

 margin is about 2 mm. from the superomarginal plates. 

 The latter are 50 or more in number, very small, scarcely 

 larger than some of the abactinal plates ; each carries an ordi- 

 nary paxilla. As a rule, they are above and opposite corre- 

 sponding infero marginals but here and there they alternate 

 with them ; often the series is not easy to distinguish. In a 

 small specimen, R=27 mm., the superomarginals are rela- 

 tively much larger ; particularly in the interbrachial arc they 

 are well-marked oblong plates, longer than wide, and forming 

 a very regular series. Terminal plate moderate, roughly 

 dumb-bell shaped, being deeply notched both distally and 

 proximally ; apparently, in life, it is covered by minute 

 spinelets, but in the preserved specimens, except the youngest, 

 these are all rubbed oft'. 



Infero marginals of about the same number as supero- 

 marginals or somewhat fewer, larger and forming a more 

 perfect series ; their paxillae are larger and carry longer 

 spinelets, but they are by no means conspicuous. Actinal 

 intermediate plates wanting at tip of ray ; the series adjoining 

 the adambulacrals begins at about the tenth inferomarginal 

 plate from tip ; a second series begins at about the seven- 

 teenth plate and a third at about the twenty-second ; at the 



L (?raa7is=slender ; in reference to the very narrow rays. 



