48 THE VOYAGE OF H.M.S. CHALLENGER. 
end of one plate lying upon the aboral end of the preceding plate. There are no pedicel- 
larize ; whilst in the type-form at this, and even at an earlier, stage they are well-developed. 
There appear to be no actinal intermediate plates, or only the smallest rudiments in one 
area. ‘There are not more than four spinelets on the actual furrow margin of the adam- 
bulacral plates directed over the furrow, but there is a similar spinelet at each extremity 
of the series, and directed parallel to the furrow. The mouth-plates have a marginal 
series of seven spinelets on each plate, the inner one being larger than the rest, and there 
is a large robust conical spine on the actinal surface of the plate, which is strongly deve- 
loped and very conspicuous. 
Locality.—Station 146. Between Marion Island and the Crozet Islands. December 
29, 1873. Lat. 46° 46’ 0” S., long. 45° 31/0” E. Depth 1375 fathoms. Globigerina 
ooze. Bottom temperature 35°°6 Fahr.; surface temperature 43°°0 Fahr. 
The close atlinity of this form to its far distant type in the North Atlantic 
is especially remarkable, whilst the manner in which some of its characters approach even 
more nearly those of Pontaster mimicus from the North-Australian Sea are very striking, 
and at the same time highly suggestive of the genetic connection of the three forms. 
Remarks. 
8. Pontaster mimicus, n. sp. (Pl. VI. figs. 1 and 2; Pl. VII. figs. 5 and 6). 
Rays five. R=78 mm.; r=105 mm. R=75r._ Breadth of a ray between the 
second and third supero-marginal plates, 10 mm. 
Rays elongate, tolerably robust at the base, tapering continuously to a finely pointed 
extremity, having a more or less rounded character laterally and especially on the actinal 
surface. Abactinal surface plane, or slightly carinate along the rays. Interbrachial ares 
rather acutely rounded. Lateral walls high at the summit of the arc, and at the base of 
the rays. Actinal surface of the disk subplane and not prominent at the mouth-angles ; 
rounded at the margins. 
The paxillze of the abactinal area are rather small and distinctly spaced. The largest, 
which are on the disk, have a crown of twelve to twenty very small, low, rounded spinelets, 
which appear only like granules when viewed from above, surrounding a proportionally long, 
delicate, tapering central spine. The presence of these spinelets imparts quite a hairy or 
subpapillose appearance to the abactinal area of the disk when viewed with the naked eye, 
the individual paxille and the small granuliform spinelets being invisible. Smaller 
paxillee formed of three to six granuliform spinelets, and without a large elongate one, are 
interspersed amongst the larger paxille on the disk. The paxille at the margins of the 
disk and along the whole length of the ray are very small, and central spinelets are only 
present on some of those along the median radial region. No definite order is discernible 
in the arrangement of the paxillee. 
The supero-marginal plates are confined entirely to the lateral wall of the ray, only 
