242 MR. H. L. CLARK ON SOME 
and rounded at tip. Abactinal skeleton almost completely hidden, even 
in the thoroughly dry specimens, by the very thick skin which covers the 
whole animal. Papulse numerous, in large irregularly-defined and more or 
less coalescent groups, absent only from the terminal fifth of the rays. 
Anus well marked by the fine calcareous papillje which surround it, nearly 
central in position. Madreporite 10 mm. from anus, small (2 mm. 
across) but distinct. Interradial pedicellarise huge and very conspicuous, 
the valves 4-5 mm. long. No other pedicellarise are present. 
Marginal plates almost completely concealed by the thick skin ; the infero- 
marginals appear to be larger than those of the up)per series, and are larger 
distally than interradially ; there are about a dozen in each series. They 
bear no spinelets, nor is the surface at all rough or shagreen-like. Inter- 
radial areas covered by thick, smooth skin, through which one can distin- 
guish some actinolateral plates, of which the series adjoining the furrow 
reaches to about the middle of the arm. Adambulacral plates about 50 on 
each side of the furrow ; each plate carries two (rarely three and even more 
rarely only one) spines, 2-2'5 mm. long, shaped like a bowling-pin, blunt, 
and even a little capitate at the tip. These spines are connected clear 
to their tips by a fleshy fold of skin. Outside this fold is the series of 
subambulacral spines, which are stouter than the furrow spines and are 
buried nearly to their tips in skin, though in the distal part of the ray they 
are more free. On some plates at the base of the arms there are two 
subambulacral spines, but as a rule there is a single one on each plate. 
Oral p)lates are not distinguishable, but they carry five, rarely six, spines 
on each side of the jaw, the most proximal largest, about 3 mm. long. On the 
surface of the jaw are four short, thick spinelets, two on each side, one 
proximal, one distal, buried in skin, and very similar to the subambulacral 
spines. Colour (dry) dull chocolate, of somev/hat varied hues, the darker 
with a purplish cast ; adambulacral spines and jaws of interradial pedicellarias, 
nearly white. 
There are two specimens of this remarkable sea-star from Pelsart Island, 
but they differ so much from each other in colour that it is hard to believe 
they are of the same species. Unfortunately the labels say nothing as to 
the colour in life, so we do not know how much of the present difference 
may be artificial. The paratype is dull greenish-yellow ; everywhere the 
outer surface layer of .«kin has cracked, permitting the deeper layer, which 
is nearly white, to show through. This is particularly marked on the 
actinal interradial areas. The interradial pedicellaria3 are smaller and 
much less conspicuous in the paratype, but there are no other differences 
worth noting. The size is essentially the same. 
The occurrence of Petricia on the western side of the continent is very 
interesting, but the Abrolhos species is verj^ different from P. vernicina, the 
species which occurs at Port Jackson and along the southern coast. The 
