Variations.—Much variation occurs in this species, as might naturally be expected
in an organism enjoying such a wide geographical range; indeed some of the divergencies
are so well marked that they have from time to time been taken by several writers
as types of distinct species. Thus Echinaster Sarsii, M. & T., is in reality nothing more
than the young phase of our Greenland form, whilst its adult stage has served as the
type of Echinaster Eschrichtii, M. & T. (= Asterias pertusa, Müller). Similarly Linckia
(Cnbella) oculata, Forbes (the Asterias spongiosa of Gould), is the shorter-armed and
more densely spinulated variety of the species, and which inhabits, as a rule, the
southern portion of the area of distribution. All these forms, however, when studied
in series, are found to fall, by imperceptible gradations, into simple modifications of the
Starfish named by O. F. Müller Asterias sanguinolenta, and earlier known to Linck as
Pentadactylosaster oculatus.
Brandt, as well as Düben and Koren, have already indicated the chief variations
that occur in this Starfish—the former classifying them under the terms of varietas
macrodiscus and v. microdiscus, and the latter authors as forma major and forma minor
(vulgans), each mentioning the main superficial characters that accompany the
lengthening and shortening of the ray. Brandt records the short-armed variety from
the west coast of the White Sea, and the long-armed one from the Ochhotsk Sea, near
•Chantar Island.
Distribution.
a. Greenland : Hare Island, Waigat Strait, lat. 70° 30' N., 175 fms. (‘ Valorous ’
Exped.), the most northern locality on record ; Egedesminde, 50 fms. (Lütken). _
b. North o f American Continent : Grand Manan (Stimpson) ; Massachusetts,
Maine, and east coast of N. America.
c. North o f European Continent : Spitzbergen {Lütken) ] Iceland, Færoe Islands,
Scandinavia, and British coasts as far south as the English Channel; White Sea
{Brandt).
d. North o f Asiatic Continent.—Sea of Ochhotsk {Brandt).
Description o f the Illustrations o f this Species on Plate II.
Fig. 18. Abactinal aspect of the animal : natural size.
19. Actinal aspect of the same specimen : natural size.
20. Portion near the middle of a ray, actinal aspect: magnified.
21. Portion near the middle of a ray, abactinal aspect: magnified.
Pedicellaster pal^ ocrystallus, Sladen. Plate II, Figs. 22-26.
1877. Asteracanthion palaocrystallm, Sladen, Ann. & Mag. Nat. Hist. ser. 4, vol. xx. p. 455.
1880. Pedicellaster pdlceocrystallus, Sladen, Ann. & Mag. Nat. Hist. ser. 5, vol. v. p. 216.
In general appearance this Starfish bears strong resemblance to a small Cribrella, the
rays, five in number, being round and tumid; they are long, somewhat swollen out on
the inner third, and taper considerably towards the extremity. The disk is small, its
radius being proportional to an arm-radius as 1: 5*5, or rather less. The ambulacral
pores are well spaced, and form two simple rows of sucker-feet. Each adambulacral
plate bears two very slender spines, one radiating towards the furrow and the other
towards the margin, forming two regular rows of so-called “ ambulacral ” spines. The
spines upon the sides of the arms are much shorter than the ambulacral spines, and comparatively
more robust, being of the same size and character as the spinelets of the
dorsal surface. The abactinal network is arranged more quadrilaterally than in Asteracanthion,
a regular median line of ossicles passing down each ray, to which the other
ossicles run parallel and transverse, with more or less regularity. A single spinelet is
borne at each decussation, and an occasional one frequently on the intercalary ossicle.
The spinelets are consequently widely spaced, and assume (although somewhat irregularly)
a fairly rectilineal arrangement. These dorsal spinelets, which are all of the same
shape and structure, resemble those of SMchaster albulus. They are deeply grooved,
being formed, in fact, of three or more longitudinal lamellae, which radiate from a
common median axis. The extremity of the shaft becomes slightly expanded and truncate,
and delicate denticles, developed from the free angles of the lamellae, are present
at the tip to the number of 3-5. In the ambulacral spinelets the outer margins of the
lamellae are serrate or denticulate, whereby, in these appendages,-a thorny appearance
is imparted to the shaft as well as to the tip.
The pedicellariae are remarkably large and numerous, and thoroughly characteristic
of the genus both in structure and position. One kind only is present, viz. the pedicellariae
. forcipiformes, which are of extraordinary size, and but very little shorter than th,e
dorsal spinelets; they stand isolated and alone upon the membranous tissue that covers
the interspaces of the abactinal network, about three or four being present in each mesh.
No traces of papulae have been detected in the membrane of the dorsal interspaces of
the examples under notice. The pedicellariae increase in size in the neighbourhood of
the ventral portion of the ray, the length of the calcareous skeleton of many of them
measuring 0'35-0*375 of a millim.* The contour of the jaws of the pedicellariae is considerably
swollen out about the upper third, and then tapers rapidly towards the extremity,
which is somewhat truncate. Several large curved denticles, usually three or
four, occur upon the median portion of the inner margins. The tail-parts of the jaw-
pieces are moderately long, and taper towards the extremity; and, when the pedicellaria
is examined from above, the interlocking lips.of the jaws are seen to be broad, rounded,
and finely denticulate. Every appendage of the body, pedicellariae and spinelets alike,
is invested with a thick, semitransparent, cuticular membrane, to which is due the papillate
appearance observable in specimens of the Starfish that are preserved in spirit. The
spines are somewhat more crowded upon the disk than upon the rays; and the “ eye ”-.
spines at the extremities form a robust terminal fringe. The madreporiform plate,
which is obscure and situated near the margin, bears only two or three striae.
* The pedicellariae on a young Asteracanthion glacialis, three or four times as large as the present specimen,
do not measure more than 0*19-0*22 of a millim.
F 2