REPORT ON THE ASTEROIDEA. 307 
ences from that type presented by the example under notice are considerable, and scarcely 
fall within the range of what might be expected in the young phases of the species referred 
to, I have considered it the safest course to regard the form in question as a distinct 
species, at least until other specimens are obtained which may throw light upon the 
relationship of these nearly allied forms. The following characters may be noticed in 
comparison with those of Nymphaster protentus as given in the foregoing description. 
In the armature of the adambulacral plates, the furrow series accord in their manner of 
disposition with those of Nymphaster protentus, but are not compressed ; the number on the 
plate is also rather less, five or six being present on those near the mouth, and eight or nine 
about the middle of the ray. The adambulacral plates are comparatively broader, espe- 
cially near the mouth, and there is no external series of spinelets as in Nymphaster protentus, 
their place being occupied by a row of granules similar in all respects to those which stand 
on the outer part of the plate. There are thus three longitudinal series of equal-sized 
granules behind the furrow series on the inner half of the ray (reduced to two near the 
middle), and there are usually five or six granules in each series. In harmony with these 
modifications in the appendages of the adambulacral plates, the armature of the mouth- 
plates is less echinulate than in the larger form Mymphaster protentus. 
Within the abactinal paxillar area, the plates of the median radial line, and the two 
parallel series on each side are oval or subcircular in outline instead of being hexagonal ; 
this shape at least being clearly defined by the marginal series of granules ; the latter are 
semiglobular and surround a central group of five or six granules on the middle of the 
tabulum. This small number forms a marked contrast to the closely crowded granulation 
of the plates in Nymphaster protentus; and, what is still more striking, the granules 
themselves are comparatively larger in Nymphaster albidus, which is the smaller 
form. 
The supero-marginal plates in the inner part of the interbrachial are are very tumid on 
the lateral wall of the disk, and extend beyond, and appear to overhang, the infero-marginal 
series. When the lateral wall of the disk is placed in the direct line of view, the line of 
suture which separates the superior and inferior series of marginal plates is seen to take a 
bold and well-defined curve, with the convexity downwards, in the inner part of the are, 
—the supero-marginal plates thus encroaching on the inferior series, the height of the 
former being considerably greater. This formation does not, however, affect the general 
thickness of the marginal wall taken as a whole. 
On the actinal area of the disk there is a considerable amount of inflation and the surface 
is convex ; there is also a slight depression of triangular form on the outer part of the 
actinal interradial area in the neighbourhood of the interradial line and bounded by the 
inner margin of the infero-marginal plates. Both the superior and the inferior series of 
marginal plates along the ray have their greatest dimension in the length, whilst in Nym- 
phaster protentus above described the supero-marginal plates are broader than long until 
