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 httle 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. dance, Verrill, or P. stellifer, Sladen, to be near allies, but in 

 reahty the present species is quite unhke 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^. 



Genus Zoroaster, Wyville-Thomson. 



Zoroaster macracantha,i gp ^q^; 



(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. ^aKp6<i=^ong-\-uKni'0a=a, thorn, or spine ; in reference to the long 

 abactinai spines. 



