SEA LILIES, STARFISHES, ETC.—CLARK. 33 
Family GONIASTERID. 
Genus Mimaster, Sladen. 
MIMASTER GRACILIS,! sp. nov. 
(Plate VII., fig. 1-2.) 
h—oosmm. =) T— tS mm.  R=3.620.- | br=8 mm: ; 
R=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 cylindrical 
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 inferomarginals but here and there they alternate 
with them ; often the series is not easy to distinguish. Ina 
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 off. 
Inferomarginals of about the same number as_ supero- 
marginals or somewhat fewer, larger and forming a more 
perfect series; their paxille 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 
‘ 1. Gracilis=slender ; in reference to the very narrow rays. 
