142] 
RECORDS OF W.A. MUSEUM. 
Actinal surface, covered, like abactinal, with a closely granu- 
lated membrane, but outlines of plates quite distinct in dried 
specimen. Inferomarginal plates, 22 on each side of a ray, corres- 
ponding exactly in position to superomarginals, and approximating 
them in size; the distal margin of each is greatly modified by the 
series of spines borne thereon. Beginning at tip of ray (to pass 
from simple to complex conditions), each inferomarginal plate 
carries at or below the middle of its distal margin a stout, flattened, 
bluntly pointed spine, rather longer than the plate and lying 
appressed to the surface of the ray and parallel with its long axis. 
On plates 4-8 a second similar but smaller spine is present, below 
(f.«. actinal to) the first; on plates g-ii, a third spine still smaller 
arises below the second ; on plates 12-14 there is a fourth ; on 
plates 15-18, a fifth ; and on plates 19-22, a sixth. On plates 20-22 
a second series of two or three spines appears, proximal to the first, 
at the base of the second and third spines of that series. With 
increase in number, there is a change of position and a marked 
increase in length of these marginal spines, so that on the median 
interradial inferomarginals, each of which bears 8 or 9 spines, the 
original first spine is 7 or 9 mm. long, and is borne on the outer 
proximal corner of the plate. 
Actinal intermediate plates rather few (25-30) aside from the 
actino-lateral series, which reaches scarcely to the middle of the 
ray ; very rarely a small spine, similar to those on the inferomar- 
ginals may be seen on one of the distal intermediate plates. Adam- 
bulacrai plates, about as long as wide ; armature in two series, 
parallel to furrow ; an inner series of 6 or 7 slender spines, median 
longest, adoral and aboral, shorter and subequal ; and an outer of 
2 (or rarely 3) very broad thin and flat, truncate spines, erect on 
surface of plate ; these flat spines are 3-4 mm. long and i-i'5 mm. 
wide. Oral plates with about 7 spines on each side, of which the 
innermost are longest and stoutest, and are distinctly prismatic; 
surface of each jaw with about 3 large, flat, thin spines similar to 
those in outer adambulacral series. 
Pedicullariae abundant and of two kinds. Scattered irregularly 
over the abactinal surface are small hivalved pedicellariae (using 
Fisher’s terminology), with jaws about half a millimetre long. Less 
common, and generally situated near a spine, are tall, 2-valved 
spatnlate pedicellariae, with jaws nearly a mllimetre high. Bi- 
