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Vlustre,
and look harder than tlie surface plates usually
do in star-fishes. The madreporic tubercle is largo
Avith sub-parallel grooves and ridges ; the excretory
opening is very distinct iu the centre of the dorsal
perisom ot tho disk. This is a very Avidely distributed
deep-Avater species. AAre met Avith it near Tristan
d’Acunha, in tlie Southern Sea, and in the North
Pacific, 'liiere is an allied species of the same genus
Fig. OS.-POTTei/niKiifercfi'tilews, W v v ille Thomson. Dorsal .surface. Natiir.al size. (No. 45.)
somcAvhat more ornate, and of an orange instead of a
blue colour in the China Sea.
The same haul gave us a singular little addition to
the family to Avhich Pourtalesia and Aceste are referred.
Aiiroije rostrata (Fig. 99) is a small species,
little more than a centimetre in length. Like Pourtalesia,
it is nearly cylindrical, and the odd interam-
hulacral area is greatly prolonged backAA'ards, and the
excretory opening brought up upon the apical aspect.
CHAP. V.] THE GULF STREAM. 3 3 1
The apex Avith a peculiar madreporic tubercle, Avith
I ff- U
large perforations and four ovarial openings with
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