68 ‘* ENDEAVOUR” SCIENTIFIC RESULTS. 
small and seemingly widely scattered. Actinolateral spines 
only 5 mm. long, hence actinolateral membranes cover a 
relatively small part of actinal surface, and actinal inter- 
mediate areas are large and densely covered with groups of 
slender, membrane-united spinelets. Adambulacral spines 4, 
the innermost very small, the outermost about 4 mm. long, 
united by a thin membrane, which retreats little (say 25%) 
between the spines, and which connects with the actinolateral 
spine. Actinolateral membrane reaches practically to tips of 
spines, with little retreat between. Oral plates with promi- 
nent central keel and very stout suboral spines (one on each 
plate), 4 mm. long, sharply triangular near tip, but truncate 
and more or less succulate ; oral spines 4, of which the first 
(proximal) is much larger than the next, about 3 mm. long, 
truncate and flat ; no membrane connects these spines. Colour 
(dry), dull grayish-brown. 
This specimen is the first representative of the genus to be 
taken anywhere near Australia. Judging by the keys to 
Pteraster which have been published one would expect either 
P. dane, Verrill, or P. stellifer, Sladen, to be near allies, but in 
reality the present species is quite unlike either of these. The 
large actinal interradial areas, the narrow actinolateral mem- 
brane and the characters of the oral armature combine to 
give P. tetracanthus a very distinctive facies. 
Loc.—South-east of Cape Everard to south of Gabo Island, 
Victoria, 90-150 fathoms. 
Family ZOROASTERID A. 
Genus ZoROASTER, Wyville-Thomson. 
ZOROASTER MACRACANTHA,! sp. nov. 
(Plate xxviii., fig. 1-2.) 
Very similar to Z. spinulosus, Fisher, from the Hawaiian 
Islands, but differing in a few details. The plates of the 
medioradial series are the largest on the arm and each succeed- 
ing series is made up of smaller plates ; the superomarginals 
are thus larger than the inferomarginals. Two series of 
actinolateral plates are confined to the actinal surface at the 
base of the arm. The plates of the medioradial series are 
provided with large central tubercles (bosses) on which are 
articulated stout sharp spines 5 mm. or more in length ; on 
the basal part of the arm such a spine occurs on nearly every 
1. waxpos=long+d«kav@a=a thorn, or spine; in reference to the long 
abactinal spines. 
