OF NEW SOUTH WALES. • 343 



nishing in size to the A. opening. Actinal cuts marked, but not 

 deep ; spines slender, tipped with violet ; shafts all shades 

 between lightest yellow and violet. Diam., 34 to 52 ; alt., 16 to 

 28 ; mil. 



Heterocentrotus trigonarius, Lamarck. 



I have lately been able to compare specimens of this urchin 

 from the Mauritius, and am now convinced that it does not occur 

 in Australia, and those specimens regarded as such are only 

 varieties of H. mammillatus , with slightly angular spines ; the 

 true H. trigonarius has the spines tapering, much more slender 

 and longer, and are very conspicuously angular, of a dark olive 

 green color, edged with red. 



Genus Schizaster, Agassiz, 1836. 

 Test thin, elongate, apex posterior ; anterior and posterior 

 pairs of ambulacra differing greatly in size, the odd ambulacrum 

 in a deep groove ; petals sunken, divergent, anterior nearly 

 parallel with odd groove ; G. pores from two to three ; 

 peripetalous fasciole angular, close to petals ; a narrow lateral 

 fasciole starting from anterior ambulacra and passing under A. 

 system with elongate triangular swellings ; posterior lip of mouth 

 prominent, beaked and curved back. 



Schizaster ventricosus, Gray. 



Test thin, outline from above broadly elliptical, angular 

 anteriorly ; apical system subcentral, posterior with vertex 

 immediately behind on the flat sloping space of medium 

 interambulacra ; petals narrowed almost to a point at apex ; 

 posterior pair of G\ pores large, round ; anterior small, forming 

 an irregular square. Posterior petals concave outwardly, 

 anterior arch only at the extremity, lateral ambulacra remarkably 

 broad, the odd one in a deep flat rectangular groove with steep 

 sides, forming a high keel in the median anterior A. space 

 extending nearly from apex to peripetalous fasciole ; the latter 

 angular, broad, especially at extremity of anterior petals, 

 re-entering on the median I. spaces ; posterior extremity broad, 



