The excretory opening is at tlie posterior extremity;
only Uvo OA’aries are developed, and the eggs appear
to be very large at the time of expulsion, corresponding
Avith the great size of the ovarial openings. The
apical plates are arranged in the usual Avay, and not
‘ disjunct ’ as in Pourtalesia, Avhich might seem to
indicate a Avide difference hetAveen the tAvo genera;
but I am inclined to think that the Aveight of resemblances
is in favour of their approximation. In
this species there is a singular ingroAvth of the
plates of the perisom Avhich causes them to overlap,
and shoAvs very distinctly, as in Calveria, that the
ambulacral ranges of plates are essentially within the
inter ambulacral (Eig. 90). The specimen examined
Avas slightly distorted.
On Saturday the 3rd we sounded in 1,210 fathoms
and lowered the dredge, AvIiich again gave us a A'ery
full sample of the fauna. Star-fishes allied to the
genus Archaster Avere once more most prominent, and
among these were several specimens of a very heautiful
little sea-star, which I propose to name Porcellanaster
ceruleus, most nearly allied to Ctenocliscus,
hut presenting many marked differences. The disk
in a full-sized example is about 20 mm. in diameter,
and length of the arms nearly equals the diameter of
the disk. The ad-ambulacral plates are large, and
each bears usually tAvo flattened someAvhat irregularly-
shaped spines. Those plates forming the angles of the
mouth are unusually flattened and expanded. The
marginal plates are of large size, and arranged in tAvo
roAvs. The surface is finely granular, and each plate
of the uj)per series bears near its inner edge a
rounded tubercle. Tlie Iavo terminal marginal plates
on each arm are fused together and hear two
diverging spines, one on either side, and above these
on the dorsal aspect a central spine set on a low
tubercle. In the re-entering angles between the arms
the two central pairs of marginal plates are closely
covered with minute flattened scales inserted on
edge and arranged in vertical rows. This is a most
cliaracteristic style of ornament; it looks as if there
Avere a little hrusli hetAveen each pair of arms. The
F ig. y i.—l'oTOiiaiicisfc)-ceriiicus, Wvvili.e T homjon. Oral siiiTiice. Natural size. (No. 4.5.)
perisom of the dorsal-surface is loaded with narroAv
calcareous plates Avhich run together towards the ends
of the arms so as to form an almost continuous
calcareous investment; paxillae are scattered over
the disk, and the outer layer of the perisom of the
disk has a very delicate colour ranging from a pale to
a tolerably strong cobalt-hlue. The calcareous plates
are clear Avhite Avith someAvliat of a porccllanous
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