100 THE ECHINODERMS OF TORRES STRAIT. 
Museum of Comparative Zoélogy from Zanzibar and Mauritius which agree so perfectly 
with Savigny’s figures that I do not hesitate to call them purpureus, even though their 
color is now, after a sojourn in alcohol of half a century, an indistinective dusky gray. 
The best of these was examined by Perrier and labeled by him vestitus, so I think we can 
safely relegate that ill-described species to the synonymy of purpureus. There seems to be 
no reasonable doubt that fallax is the same thing, as has been generally assumed. In regard 
to luzonicus, it is clear that Gray supposed it to be distinct from purpureus and points out 
its longer rays and its reddish-brown color as marks of distinction. Now, it is obvious, 
when the Torres Strait sea-star is compared with specimens from Mauritius, that they 
are not strictly identical, and for the present I think it is best to keep them separate, using 
purpureus as the name for the western form and luzonicus for the eastern. As for eridanella, 
it is undoubtedly a synonym of luzonicus. Regarding the generic name, I think it possible 
that the species of the tropical American seas and those of the Indo-Pacific region are not 
all Echinaster in a strict sense, but I have not been able to find a satisfactory line between 
Othilia and Echinaster, so I am not using the former name. Very likely a careful revision 
of the family will result in the satisfactory definition of each group, with the use of 
both names. 
The differences between LZ. luzonicus and E. purpureus may be expressed as follows: 
R=6-7r and 5.5-6.5 br, with rays terete but stout; adambulacral plates commonly without a subambu- 
lacral spinelet near marginal spinelet, so there is a wide bare space, with or without spinelets, 
along the actinal surface of ray each side of the furrow (well shown in Savigny’s figures) ; 
actinal spinelets few and relatively large. Color red-purple or deep purple, the color more or 
less retained or becoming ashy when dry. Found from Zanzibar to the Red Sea and at Mauritius Z. purpureus 
R=7-10.5 r and 7-10.5 br, with rays more cylindrical and often very slender; adambulacral plates com- 
monly with a distinct subambulacral spinelet, near the margin, so there is no conspicuous bare 
area on each side of the furrow; actinal spinelets rather numerous and small. Color rusty or 
red-brown, or in life, dark olive-brown and even almost black, but with no trace of purple; 
preserved specimens some shade of yellow-brown, brown, or dark red-brown, sometimes with 
a green cast. Found from Ceylon and the Philippines to northwestern Australia, Torres Strait, 
New) Britain,jandieven. New Caledoniaty. 2 .i5)a2 sj saiscleisiote sre © locale clove ete oslo loveiele omersiel sts E. luzonicus 
Whether these differences are entitled to be considered specific remains to be deter- 
mined. They are certainly not as yet perfectly constant or firmly fixed. 
About the Torres Strait islands, Echinaster luzonicus occurs exposed on sandy or even 
muddy flats in shallow water, often where considerable ‘‘eel-grass”’ (Posidonia) is growing. 
When removed from the water they contract perceptibly, and water is forced from the anus 
in a stream 25 to 50 mm. high, reminding one of the ejection of water from the respiratory 
tree of a holothurian. This naturally suggests that the so-called ‘‘rectal gland”’ is in 
reality a respiratory organ of much importance. 
METRODIRID£E. 
Metrodira subulata. 
Gray. 1840. Ann. Mag. Nat. Hist., 6, p. 282.—Koehler. 1910. Ast. et Oph. des files Aru et Kei, p. 284; 
pl. xv, fig. 3; pl. xvii, figs. 3, 5—Indian Mus. Ast. p. 172, pl. iv, figs. 1, 2; pl. xviii, fig. 9. 
Koehler’s very full and well-illustrated accounts of this remarkable sea-star leave 
nothing for me to add, since we did not meet with it in Torres Strait. The Challenger, 
however, took a specimen near Wednesday Island, and according to Bell the Alert collec- 
tion contained specimens from ‘‘Flinders, Clairmont; Alert Island, 7 fathoms.’”’ As near 
as I can interpret these localities, from Dr. Coppinger’s notes and other parts of the Alert 
1 Bell (1899, p. 138) records (with that brevity on which he frequently prides himself but which is very trying 
for his colleagues in search of information) both HZ. purpureus and E. eridanella in Dr. Willey’s collection, but he does 
not say how he distinguishes the two. This is unfortunate for in at least one case he has identified as Z. purpureus 
the very different Metrodira subulata (q.v.), and I do not think the true E. purpureus occurs on the coast of New 
Guinea or in the islands to the east thereof. 
