134 THE VOYAGE OF H.M.S. CHALLENGER. 
HASTERN ARCHIPELAGO: One species between the parallels of 0° and 10° S. 
Porcellanaster caulifer in the Arafura Sea, between Australia 
and New Guinea. 
8. Bathymetrical range: 800 fathoms to 2550 fathoms. 
All the species are confined to the Abyssal zone, and one only (Porcellanaster 
caulifer) is found at a less depth than 1000 fathoms. Three species, Porcella- 
naster crassus, Porcellanaster gracilis, and Porcellanaster eremicus are found 
in depths greater than 2000 fathoms. 
Porcellanaster cxruleus is the only species known to me from more than one 
locality, and its range is very constant, varying only from 1240 to 1850 fathoms. 
y. Nature of the Sea-bottom - Three species are found on the Blue mud, viz. : 
Porcellanaster cxruleus in the Atlantic, and Porcellanaster gracilis and 
Porcellanaster tuberosus in the Pacific. Porcellanaster crassus and Porcel- 
lanaster erenucus are found on the Red clay in the Pacific and South Atlantic 
respectively. Porcellanaster caulifer lives on Green mud in 800 fathoms. 
Chorological Synopsis of the Species. 
Ocean. Range in Fathoms. Nature of the Sea-bottom. 
Porcellanaster cxruleus  . . | Atlantic. 1240 to 1350 Blue mud. 
Porcellanaster caulifer . |j ; astern Archipelago. 800 Green mud. 
Porcellanaster crassus ; . | Pacific. 2335 Red clay. 
Porcellanaster eremicus  . . | Atlantic. 2550 Red clay. 
Porcellanaster gracilis. . | Pacific. 2225 Blue mud. 
Porcellanaster tuberosus . . | Pacific. 1875 Blue mud. 
1. Porcellanaster cxruleus, Wyville Thomson (Pl. XX. figs. 1-7). 
Porcellanaster ceruleus, Wyville Thomson, 1877, Voy. of Challenger, Atlantic, ‘vol. i. p. 378, figs. 
97 and 98. 
Rays five. R=22 mm.; 7=10°5 mm. (the largest example). R=2 1, approxi- 
mately. 
Marginal contour substellate, with moderately developed rays proceeding from a 
truly pentagonal body-disk, the minor radius being in the proportion of 48-50 per cent. 
When viewed from above the rays seem comparatively small and have the appearance 
of springing somewhat rapidly from the angles of the disk, the interbrachial are being 
very wide and not unfrequently quite straight, or even curved outward, rather than 
rounded. Disk more or less gibbous and inflated, the height being sometimes equal to 
one-third of the greatest diameter, but generally less. The arching or inflation of the 
