to each adambulacral plate, owing to the plates which hear the spines being more widely
spaced. The abactinal body-frame is formed of transverse bands of ossicles; and these
are packed closely together in longitudinal series along the ray: the plates axe very
uniform in size; and as each generally stands opposed to a corresponding plate in the;
neighbouring transverse row, a fairly regular rectilinear arrangement is the result. The
median ossicles, which are somewhat larger than the rest, imbricate upon one another
and form a distinct line along the ray. The membranous interspaces are of moderate size
and punctured with one or two papulse. Each ossicle bears a small subquadrate group
of from three to five short dorsal spines, amongst them being placed two or three of the
pedicellarise forcipiformes, but which are somewhat more numerous towards the sides of
the ray. The spine-groups, in consequence of the regularity of the network, are disposed
in longitudinal and transverse lines, those of the middle row being rather larger and more
densely packed than the others, and thereby forming a more or less distinct median
line down each ray. From the apices of the spines, which are broader than the bases,
proceed three or four small denticles; and the spinelets being all of equal length and
closely set, give a smooth velvet appearance to the Starfish. Pedicellarise forficiformes
are found along the margins of the ambulacral furrow at intervals of every two or three
plates, but are comparatively small in size, short, and somewhat rounded or obtuse at the
points. Two or three larger ones are frequently met with in the neighbourhood of the
actinostome, often quite gigantic; and a few isolated individuals also occur on the dorsal
surface, but seldom beyond the base of the rays; these, it need scarcely be said, are
considerably larger than the p. forcipiformes which accompany the spine-groups above
mentioned. The p. forcipiformes that occur on the lateral portions of the rays are, as
a rule, situate on the aboral or outward side of the spines. The madreporiform body
is situated near the margin, and is large, simple (having but few striae), and surrounded
by a circlet of the dorsal spines.
Size.—This species seldom measures more than from one inch to an inch and a
half in diameter, and is generally less. A variety, noted below, is recorded from
Eastport 4 inches in diameter.
Colour.—In a living state Stichaster albulus is described as of a faint red or
cream-colour. When dried, or in spirit, it is usually light yellow, varying to more or
less warm shades of light brown.
Habitat.—On stony ground and Laminaria in 5-20 fathoms, and seldom in greater
depths (Olrik). I t has been taken by Barrett in from 3-25 fathoms, also on stony
ground (Lutken, l. c. p. 30). Verrill similarly records its occurrence on the coast of
Maine and Grand Manan, in 10-20 fathoms, on rocky bottoms and among Nullipores,
and frequent also at low water of spring-tides among rocks (l. c. p. 351). Stimpson
states that at Grand Manan the species occurred most frequently among branching
Nullipores in 4 or 5 fathoms on the east side of the island.
Variations. Although the number of rays in this species is almost invariably six,
about two per cent, of the specimens collected have only five, according to Stimpson’s
observations at Grand Manan; and examples with seven occur occasionally. The same
authority also records that four out of five had three of the rays much larger than the
others.
Verrill has described * a variety under the name of nitida, taken at Eastport, Maine,
at low water, but which, in his opinion, presents no peculiarities which may not
be considered due to increased age. The specimen is remarkable for its large size
(4 inches in diameter) and regular form. The rays are equal, and the median row of
plates quite distinct. The lateral spines are four or five in number, in a transverse
row, those nearest the ambulacra being longest. The adambulacral plates bear two,
three, or sometimes four long, tapering, and rather slender spines. The dorsal plates
are crowned by eight to twelve small, somewhat radiating spines, thicker and more
obtuse than those of the ordinary variety. The papulae are not very numerous, rather
large, and occur mostly in pairs. Suckers numerous and much crowded, in four
rows.
Judging from the description alone of a single specimen, it would be difficult to
say whether the modifications above noted possess any greater significance than mere
conditions of growth. Augmentation in the number of ambulacral and lateral spines,
as well as of those upon the ossicles of the disk, greater development of the median
row, increase in the number of papulae, and crowding and increase of the ambulacral
suckers, are, it is true, changes that accompany structural growth; still, if we are
only to give these characters such a value in the present case, it seems strange that the
form in question is not of more frequent occurrence in localities where Stichaster
albulus may be taken in the utmost abundance.
A single large example which may be referred to this variety was dredged at
Proven during the outward journey of Capt. Nares’s Arctic Expedition, the diameters
of the rays and disk being respectively 30 millims. and 6 millims.
Comparing specimens from the coast of Maine with those from Franklin-Pierce
Bay (lat. 79° 25' N.), we have detected no remarkable difference; and Mr. Verrill records
the same conclusions in regard to specimens from Greenland which he had studied.
Distribution.
a. Northward o f Smith Sound: Franklin-Pierce Bay, lat. 79° 2 5 'N., 15 fms.
(Nares’s Exped.), the most northern locality on record.
In Davis Strait: Godhavn Harbour and Holsteinborg (‘ Valorous ’ Exped.);
Proven, 13 fms. (Nares’s Exped.).
• b. North o f American Continent: Grand Manan (Stimpson); Eastport, Maine
(Verrill).
c. North o f European Continent'. Spitzbergen (Lutken)', Iceland, Ofjord (Lutken).
Description o f the Illustrations o f this Species on Plate II.
Fig. 13. Abactinal aspect of the animal: natural size.
14. A larger and almost equal-rayed variety from Proven.
* Proceed. Boston Soc. Nat. Hist. vol. x. p. 351.