OF NEW SOUTH WALEB. 153 



Port Jackson, Swansea, Tasmania, King's Island, Hobson's Bay, 

 Sealers' Cove, Portland Bay, Guichen Bay, Encounter Bay, and 

 generally on South Australian coasts. 



The family ARBAClADiE is not represented on the Australian 

 coasts. 



Family Diadematidje, Peters, 1853. 



Test thin, with a bare forking I. space. A. narrow. Is 

 depressed near abactinal system. Spines long, exceeding test, 

 hollow, verticillate- Tubercles of both areas similar. Actinal cuts, 

 moderate. 



Genus I. — Diadema, Schynvoet, 1711. 



Test slightly pentagonal, flattened at both poles, thin. 

 Tubercles in two vertical rows, those of A. smaller than I. 

 perforate and crenulate. Porif. zones narrow. A. narrow com- 

 pared to I. and often rising considerably above them. Pores in 

 simple pairs, forming arcs round adjacent tubercles. Actinal 

 system large, cuts 10, broad, but not very deep. Membrane 

 strengthened by small limestone plates. Anal system covered by 

 a thin naked membrane, anal openings at end of a tube, extending 

 like a proboscis beyond anal system. 



Diadema setosum, Gray. Easily distinguished by its long 

 slender needle-like hollow spines, extending three or four times 

 the diameter of test. Dusky in colour, but banded with darker 

 spaces. The colour of the test is blackish, on which the white 

 tubercles are very conspicuous. Many specimens were obtained 

 by Mr. Macleay, from Darnley Island, 10 to 20 fathoms, on sandy 

 mud bottom. It had been found hitherto in almost every tropical 

 sea, except the Australian. 



Genus II. — Centrostephanus, Peters, 1855. 

 Test globular, buccal plates 10, all carrying spines, no bare 

 forking interambulacral space. Abact. syst. nearly circular, and 

 covered by distinct plates. Tubercles of both areas similar, crenu- 

 late, perforate, and arranged in two vertical rows in the I. zone. 

 Spines stouter in shape than last genus, but more hollow, being 

 mere shells. Actinal openings slight. Pores in arcs of three. 



