146 THE ECHINODERMS OF TORRES STRAIT. 
species, and it seems to me obvious that he has confused them in his colored figure as well 
as in the text. If not, his specimen of setosuws was exceptionally light-colored. Mortensen 
lists savignyi from Zanzibar, but says it does not occur in the Gulf of Siam. The Albatross 
found it at Easter Island, which indicates the greatest possible range for an Indo-Pacific 
species, considerably more than 14,000 miles east and west. 
Centrechinus setosus. 
Echinometra setosa Leske. 1778. Add. ad Klein, p. 36. 
Diadema setosa Gray. 1825. Ann. Phil., 10, p. 4. 
Centrechinus setosus Jackson. 1912. Phyl. Ech., p. 28. 
(Plate 17, Figures 3 and 4.)! 
The genus Centrechinus is a perplexing one, because in Museum specimens the species 
resemble each other so closely it is difficult to detect constant differences. But observations 
in the West Indies and in Torres Strait have satisfied me that there are important specific 
differences in color, and, when these are properly known, the separation of the species will 
not be so difficult. At Mer two species of Centrechinus occur, and they are so unlike in 
color that any one can distinguish them at a glance, and neither is like the West Indian 
form. One of the Torres Strait species is characterized by white markings, five spots, 
dorsally in the interradii (pl. 17, fig. 3) and the whole oral region (pl. 17, fig. 4). Further 
distinguishing characters are found in series of blue spots bordering the dorsal interam- 
bulacra near the ambitus, but converging and forming a single line between the white spot 
and the periproct, and in the bright-orange anal region (pl. 17, fig. 3). Comparison with 
good museum material shows that this is the species common at Amboina, the type-locality 
for setosus, and I do not hesitate to identify it with Leske’s species. It was the first Cen- 
trechinus we met with in Torres Strait, a large specimen being found at Prince of Wales 
Island. We subsequently met with it at Erub and Mer, but it was not nearly so common 
as the next species (savignyi). The two species did not occur actually together, but both 
were found at various points all over the southeastern reef-flat. Even in small specimens 
of setosus the white spots are evident. There is some diversity in the ground-color of the 
animal, for while adults appear to be perfectly black, they often have a purplish tinge, and 
young specimens are purplish or brownish with banded spines. 
It is not possible to discuss the distribution of setosus with much profit, for most 
records published hitherto confuse all the Indo-Pacific species of the genus under one 
name. We know that the present species occurs on the Queensland coast at Palm Islands, 
and I found a Centrechinus at Green Island, but did not note the species. Amboina is 
certainly the home of setosus, and Mortensen (1904) describes specimens from the Gulf of 
Siam. He adds that he has seen specimens from Zanzibar and from Tahiti, so there is 
little doubt that it occurs throughout the Indo-Pacific region. 
Echinothrix calamaris. 
Echinus calamaris Pallas. 1774. Spice. Zool., 1, fase. 10, p. 31. 
Echinothrix calamaris Peters. 1853. Monatsb. Akad. Berlin, p. 484.—Déderlein. 1903. Jena. Denkschr., 
8, pl. lix, fig. 9; pl. lxiii, fig. 6. 
This fine sea-urchin has a typical Indo-Pacific distribution from Mozambique and the 
Red Sea to the Hawaiian and Society Islands, and even further southeastward to the 
Paumotus. It does not seem to have been recorded from the Australian coast, and I did 
not see it at Green Island. But at Mer it is by no means rare. Several specimens were 
1 In order to make the plan of coloration perfectly obvious, I suggested to Mr. Grosse that he leave out the 
spines in drawing Centrechinus and show only the test with its characteristic color-pattern. The result is very satis- 
factory, except that the illustrations do not look like Cenirechinus! And the somewhat hemispherical test becomes 
too flat when printed so black. 
