O ph iogly pha robusta, Ayres, sp . P la t e I V , F ig s . 6 - 7 .
Qpjiiolepis robusta, Ayres, Proe. Best. Soo. N. H. iv. 1851.
Ophiura squamosa, Liitken, Yid. Meddel., Nov. 1854.
An Ophioglypha with arms very finely tapering, and disk with regularly arranged
scales of nearly equal size. Mouth-shields ovate shield-shaped; length less than, or
at most only equal to, their breadth; length much less than the distance from the
margin of the disk. Papillae of the disk-incision very short and stout, often grouped.
Under arm-plates broadly heart-shaped; one tentacle-scale.
This species was obtained at various stations, as indicated in the list of localities;
and though neither the abundance nor the size of the specimens was remarkable,
several good series were collected. The characters which have been regarded as
“ specific p are remarkably constant; and no essential difference can be traced between
these Arctic forms and specimens taken from the coast of Maine, U. S., with which
they have been compared, excepting that in the northern Ophiurans the arm-spines are
longer and somewhat more delicate, and that the outer margin of the under arm-plates
is more arched, and the reentering angle is far less developed, being even altogether
untraceable in certain specimens. In some large examples the upper arm-plates are
very markedly hexagonal. Although this deviation is very constant, the foundation of
a <s variety ” on the strength of such characters alone, is hardly justifiable.
The arm-spines are moderately stout and tapering, the upper one being flattened
and much larger than the others.
In most of the specimens under present consideration the under arm-plates are
well separated from one another by the side arm-plates, and do not overlap, although in
one individual from Discovery Bay the first ten impinge distinctly, in consequence of
their side arm-plates not meeting. This feature at the basal portion of the arm has
been noted by Dr. Liitken as occurring in large specimens from Greenland, whilst he
remarks at the same time that in none of the Danish examples examined by him do
the under arm-plates touch.
Coll. Feilden.—Discovery Bay, 25 fms., hard bottom; Richardson Bay, 70 fms.;
Hayes Point, 35 fms., bottom temperature 29°*5, and also at 25 fms.; Franklin-Pierce
Bay, 15 fins., bottom temperature 25°*5.
Coll. Hart.—“ Winter quarters,” Discovery Bay; Franklin-Pierce Bay, 13-15 fms.,
bottom stony.
The largest specimen was taken by Capt. Feilden in Franklin-Pierce Bay, the
diameter of the disk (dried) being 10 millimetres.
The scaling of the upper part of the disk is very variable in its pattern, relative
size, and colour. In one specimen the usual smaller scaling is in the centre, and the
larger around; but the central scale is almost circular in outline, and is surrounded
by smaller ones, some of which are triangular, with the apex broadly rounded and the
intermediate one rhombic. This produces a curious, rosette, eminently crinoidal in
its configuration, but flat. The ornamentation of grains of calcareous matter on these
scales is very beautiful; it radiates in numbers of separate and close lines of granules
from the centre of the central scale to the outside of the bluntly triangular scales; and
the rhombic scales and the others around them, which are not very definite in shape,
have their ornamentation radiating from their own centres.
In another specimen the scaling is perfectly irregular, no sign of a rosette appears,
and the large radial shields are separated by several small scales in some radii and not
at all in others, when one large overlapping scale is placed between, or rather overlaps
their oral and diverging median line. In other specimens where there is a rosette the
oral separation of the radial shields is by three large plates, one being flanked by others,
or by two plates, one large and one small, the latter being aboral to the other. The
ornamentation is not so much by grains as by cells which are not yet opaque with
carbonate of lime. The radial shields are convex, large, and are broadly convex where
more or less free aborally; they are separated aborally by small upper arm-plates, in
some instances two, and in others three in number. The shields, thus separated aborally,
and, as has been mentioned, orally, are united in some instances along a very short
line. With regard to the upper arm-plates within the notch, the first is often more
or less triangular in shape, with rounded edges, and the apex is oral; and when this
shape prevails, this plate is usually larger than the second, which is broad, short, and
sometimes notched distally. The third is larger, and shaped more or less like the
second.
The spinules, which are stout, distinct, and more or less grouped in two rows, are
not often more than six or eight in number. They are beyond the radial shields, and
appear to be on the derm between them and the upper arm-plates. I t is evident that
in some specimens there is a spine, or even two (but not in all radii of one specimen),
on either side of the first and second arm-plates, and even on the third. This distribution
of a few well-developed, short, stout, blunt spines is very characteristic. In some
specimens, and in the largest, the first upper arm-plate is in two pieces.
The coloration of the upper part of the disk varies from a perfect white to a
spotted state, with indefinite blue, black, and white, and brown and white. Blotches
appear on the centres of the radial shields and larger plates, eo that the whole assumes
a maculated appearance. The slate-blue colour, very light in its intensity, may prevail
so much on the disk that the white parts come out very decidedly; and usually that is
the colour of the third row of the rosette, of the scales external to the radial shields,
and of some scales in the interbrachial spaces near the edge.
The upper arm is banded in some specimens with the disk-colour and white; and
usually the colour is lost towards the termination of the arms.
The upper arm-plates are much more convex in their distal curve in some specimens
than in others; but in all they are much broader than long near the disk, and in
mid-arm take on the kite-shape with the angle oral and the convex curve distal.
Gradually they become longer than broad; and towards the end of the arms the side
arm-plates meet above.
There is some variation in the shape and size of the mouth-shields; but their acute
oral angle and broad aboral part are invariable. The side mouth-shields are small,
narrow, much curved, and just reach to the end of the generative slit. Owing to the
angular nature of the proximal part of the mouth-shields, the side mouth-shields, with