RECORDS OF W.A. MUSEUM. [Hi 
STELLASTER MEGALOPREPES, ' sp. nov. 
Plate XVIII. 
Rays 5. R=i2o mm. r. = 45 m. R. = 2fr. Br at base = 4o mm. ; at 
half-way point, 24 rnm. Interbrachial arcs well rounded. Disklarge, 
not highly arched, yet distinctly convex; vertical diameter about 
20 mm. Entire abactinal surface covered by a closely granulated 
membrane, obscuring but not actually concealing the out- 
lines of the underlying plates. Superomarginals, 22 on each 
side of ray ; median interradial pair about 12 mm. high by 4 
mm. wide, but distally the height decreases with little change in 
width, the fifteenth plate from the interradius being about 6 mm. 
high by 3.5 mm, wide (or long). At the tip of the ray the 19-21 
superomarginals of the two sides are in contact abactinally but the 
twenty-second pair are so small, they are completely separated from 
each other by the twenty-first pair being in close contact with the 
rather large terminal plate. Abactinal ends of superomarginals 
(except distalmost) rounded wedge-shape, with a group of papulae 
on either side. No spines, tubercles or pedicellariae on any supero- 
marginals. Abactinal skeletal plates small, largest in interradial areas, 
where the}' may measure nearly five millimetres across. Median 
radial series consists of about forty plates and runs to a point about 
nine or ten millimetres proximal to tip of ray, where meeting of 
superomarginals of opposite sides puts an end to abactinal plating. 
On each side of median radial series, at base of arm, are two parallel 
series of somewhat smaller plates ; the one adjoining the median 
series runs about as far as the fifteenth superomarginal while the 
outer one ends at the eleventh or twelfth. Excepting thirty (more 
or fewer) distal, medial radial plates and about ten or a dozen distal 
plates in each of the two adjoining series, all abactinal plates carry 
sharp conical spines ; the largest are situated one at the base of each 
ray on the first of the tnedian radial plates ; these five spines are 
about five millimetres high and two in diameter, at base ; most of 
the spines are two millimetres high or less, but all if uninjured are 
very sharp. Papulae numerous but rather small, in groups of 
3-20, all over abactinal surface ; largest groups between upper ends 
of superomarginal plates. Madreporic plate, 7mm. long by 6 wide, 
rounded triangular, its proximal margin 12 mm. from centre of 
disk. Arms very distinct. 
Gr. megaloprepes — magnificent, splendid. 
