SEA LILIES, STARFISHES, ETC.—CLARK. 4] 
in alcohol, brownish-yellow; dry, pale brown. Seven 
specimens. 
This fine species is obviously near to Mediaster ornatus, 
Fisher, from the Hawaiian Islands, but differs in the wider, 
shorter marginal plates and in the adambulacral armature. 
No other member of the genus is very closely allied. As 
regards the internal anatomy, the Australian species is a 
typical Mediaster, the internal abactinal ossicles being very 
evident and rudimentary superambulacral plates also being 
present. 
Locs.—Kast coast of Flinders Island, Bass Strait, 40 
fathoms. This specimen has been selected as the holotype. 
East of Babel Island, Bass Strait, 65-70 fathoms. 
Oyster Bay, Tasmania. 
MEDIASTER MONACANTHUS,! sp. nov. 
(Plate x., fig. 1-2; Fig. 4.) 
ho lmms, Ts (mm: iyo ht "br=—o7 mmo be 
3 br. Br at middle of ray=19 mm.; at tip=5 mm. Disk 
large, flattened or slightly elevated; arms wide at base, 
tapering rather evenly to the blunt tip. Abactinal plates on 
disc and base of rays large, low, hemispherical, widely spaced, 
becoming smaller and more and more crowded near the supero- 
marginals ; they are connected with each other by heavy 
radiating ossicles, in the spaces between which the papule 
arise in groups of 3-15. Hach plate is covered by a coat of 
low, spherical granules ; there are about 50-75 on a plate 4-5 
mm. in diameter ; there are no granules on the membrane or 
on the ossicles between the plates. In the holotype, and some 
other specimens, most of the disk plates bear at the centre a 
pointed tubercle or low, blunt spine, about a millimeter in 
diameter and nearly or quite as high; in some specimens few 
or no plates have this spine, so it may be an indication of 
complete maturity. Distally on the rays and near the 
margins of the disk, the plates become smaller and crowded, 
so the granular covering is nearly or quite continuous. 
Madreporite very small, only about 2 mm. across, situated 
twice as far from the margin as from centre of disk. Anus 
conspicuous near centre of disk because surrounded by 10-20 
large, smooth, elongated granules of diverse size and shape. 
1. pwovos=single+ dxav@a=a thorn or spine ; in reference to the single 
prominent spine on some abactinal plates. 
