the ray stands at the same angle to the plate, and thus two regular rows are formed on
either side of the furrow. In others, however, each alternate pair of spinelets radiate
at a rather smaller angle to the floor of the ray, the internal spine being directed
further over the furrow, and the external one standing opposed to the interspace between
the pairs of spinelets of the neighbouring plates; by this means an arrangement of
four rows of spinelets on each side of the furrow is brought about, which, together
with the swollen character of the sides, gives an appearance of considerable breadth to
the ventral portion of the rays. The ambulacral spines are long, cylindrical, and
rounded at the tip, not tapering or pointed in the slightest; and the innermost spine is
somewhat thinner than the others. Pedicellarise forficiformes are very numerous
amongst the rows of ambulacral spinelets, and are densely crowded at the base of the
rays in large specimens. The lateral spines, which are long, cylindrical, and somewhat
crumpled or nipped together at the tip, form three longitudinal rows extending along
the ray. In addition to these there is a short secondary row situate between the most
ventral of the lateral series and the ambulacral spines; but, in consequence of the
rapidity with which the spinelets diminish in size as they proceed outwards, this series
extends only along the inner half of the ray.
In some large specimens there is often a short row of 6—8 supplementary spines at
the base of the ray between the ventral and middle series of lateral spines; or a
tendency to reduplication may be shown even in each of the rows at the extreme base
of the ray. Occasionally the lateral spines are more or less tapering, those of the
dorsal and median rows being also slightly curved upward.
The calcareous network of the abactinal surface is very robust, the membranous
meshes or interspaces being in proportion comparatively small. The papulae are, as a
rule, single in young specimens; but in those of larger growth two or three occur
together. The dorsal spinelets are large and cylindrical, not tapering, but- nipped
together at the tip, or even sometimes subclavate as in A. violaceum. They do not
assume any lineal or regular arrangement whatever upon the abactinal surface. In
some examples the dorsal spinelets are closely surrounded by a number of rather
smaller subclavate spinelets, which give the appearance of compact groups of spines
crowded together upon the abactinal surface of disk and rays alike.
Pedicellarise forcipiformes, although very numerous upon the abactinal membrane,
cannot be strictly said to form regular wreaths at the base of the dorsal spines; for
whilst in some places they are much crowded, in others only three or four are present.
In the lateral series, however, the spines of the upper or dorsal row are surrounded at
their bases by a true wreath of pedicellarise, whilst in the ventral or lower row the
pedicellarise are principally grouped on the dorsal or upper side of the base.
The pedicellarise forficiformes, which are moderately numerous upon the abactinal
surface, averaging perhaps one or two to a mesh, are densely crowded amongst the rows
of ambulacral spines, especially on the innermost portion of the furrow. These pedicellarise
(p. forficiformes) are in the present species comparatively small, only a little
longer than broad, and dumpy in form; the p. forcipiformes, on the other hand, are
large, very gibbous, and truncate at the apex of the jaws.
S 3S 9 3 .'im*.
The madreporiform body is situated in the interradius, about midway between the
centre and the margin of the disk, but generally nearer the centre in fully developed
specimens.
Size.—Large examples measure 230 millims. in diameter; and the species is known
to attain even greater dimensions.
Colour.—Dr. Lutken, recording the observations made by Inspector Olrik upon
the colour of this Starfish when alive, states that it is generally purple-red, and sometimes
greyish olive-green.
Habitat.—According to the above-mentioned Danish naturalist, A. polare is to be
found at low tides in May and June, but later in the year in deeper water (for instance,
in August at 40 fathoms). This species was taken at Arksut by Mr. Barrett, from the
shore down to 10 fathoms depth, on rocky bottom.
Premature Form.—A young specimen. 28 millims. in diameter (the relative
proportions of the disk and radii being 1 3'5 approximately) presents the following
characters. The rays are broad and stout, tapering near the tip, and have then-
junction with the disk very frequently marked off by a sharp constriction in examples
of this early age. The ossicles of the abactinal network are remarkably stout and
robust, the interspaces being small and restricted in consequence; these are usually
round in outline, with the membrane punctured by a single papula only, although two
may occur occasionally. The dorsal spinelets are large and truncate, many quite subclavate,
and are widely spaced over disk and rays alike without any regularity in their
arrangement ; their bases are closely surrounded by pedicellarise forcipiformes, the
large size of which is very striking in this young stage of the- starfish, whilst similar
pedicellarise also accompany the secondary or intermediate spinelets, which occur with
moderate frequency upon the imbricating ossicles. In the small specimen under notice,
no pedicellarise forfioiformes have been detected upon the abactinal surface either of
the disk or rays; there are, however, a few isolated ones on the margins of the furrows,
but comparatively insignificant in size, and scarcely, if at all, larger than the p. forcipiformes
of the abactinal surface.
The madreporiform body, which is large and deeply fissured, lies nearer the margin
than in the adult forms, being situated about two thirds of the distance from the centre
of the disk to the arm-angle.
Two longitudinal rows of lateral spines sue present, one on the dorsal and the other
on the ventral margin, the sides of the ray being vertical. The;spinelets of both series
are large, stout, cylindrical, and rounded at the tips; they are isolated and well spaced,
the members of the upper series standing immediately over their ventral companions.
In dried specimens the dorso-lateral row forms a conspicuous fringe along the margins
of the ray, and the bases of the spinelets are surrounded by a wreath of pedicellarise
forcipiformes. These are also present at the bases of the ventro-lateral series, though
not so numerous, and are there confined principally to the upper side of the spinelet.
Between the ventro-lateral row and the ambulacral spines a short series of secondary
spinelets extends along the inner half of the ray only; these are smaller, even at the
base of the ray, than the other spinelets, and diminish rapidly in size as they proceed
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