RECORDS OF W.A. MUSEUM. 
[137 
wtiich are a pair of plates of about equal size. Distal to them is a 
series of three or four plates. Theoretically this series is succeeded 
by one of six and that by one of eight plates, the median four of 
which abut on the inferomarginals. Actually, however, these last 
tvvo series are irregular in number, form, size and position of the 
plates. In any case, however, the plates which abut on the infero- 
marginals are the smallest and those next the mouth plates are the 
largest of the actinal intermediate plates. 
The adambulacral plates are about twice as wide as long. 
Their armature consists of a series of three stout, blunt, somewhat 
prismatic, furrow-spines, of which the middle one is either the 
largest or the smallest. This series is parallel to the furrow, and 
directly back of it, on the surface of the plate, is a second series of 
similar, but shorter and stouter spines. There may be either two 
or three spines in this series but three seems to be the typical 
number and when there are only two they are exceptionally stout. 
The remaining surface of each plate is covered by six to ten small, 
low, truncate, prismatic spines, arranged in series of three (rarely 
two or four) parallel to the furrow ; the outermost are very similar 
to the granules surrounding the actinal plates. The armature of 
the oral plates consists of six large marginal spines on each side of 
the “ jaw,” the two at the apex being the largest. On the surface 
of each jaw there are six to ten similar but smaller spines (three to 
five on each side) while the low keel of the jaw is concealed by 
about eight thick prismatic spinules arranged in a double series. 
Excavate pedicellariae, similar to those of P . pidchelhis and P. 
duheni, but smaller than those of the former and larger than those of 
the latter, occur on many of the abactinal plates. None were found 
on the actinal surface of either specimen. They occur irregularly 
scattered and may be present on any plate, but no plate carries 
more than one. They may have either two or three valves; in the 
smaller specimen they are mostly two- valved, but in the t}pe, the 
three-valved form predominates. 
Colour of type, very pale fawn ; the smaller specimen is brown- 
yellow. In life, the colour of both was “ bright orange.” 
Between Fremantle and Geraldton, W.A. 40-100 fms. Two 
specimens. No. 4916. The larger specimen is the Type. 
This species is obviously related to P. dubeni, Gray, but is at 
once distinguished by its much broader rays, covered by nearly 
