154 THE PROCEEDINGS OF THE LINNEAN SOCIETY 



Centrostephanus Rodgersii, A. Agas. Thin, very spiny, 

 urchin with long stout but very brittle spines of deep reddish 

 purple colour. It is not uncommon about Botany Heads, at low 

 tides in a few feet of water. 



Genus 3. — Astropyga. Gray, 1825. 



Test so thin that it is more or less flexible, greatly depressed. 

 I. sunken frequently far below the bulging A. Bare median I. 

 space forking, and each plate having a colored pit. Tubercles 

 uniform, perforate crenulate, two vertical rows on the L, many 

 on the A. Spines rarely attaining half diam. of test, uniform, 

 slender. Porif. zone, rather broad, pores, in four irregular vertical 

 rows. Anal system plated, but not otherwise different from 

 Diadema. 



Astropyga radiata. Leske. A large depressed test of dull 

 whitish green and reddish brown. The anal system and bare 

 median I. space are reddish with spots of violet. The spine 

 slender, generally red. This species has been known to naturalists 

 for more than a century, but has never before been found in 

 Australia. Four large specimens were dredged by Mr. MacLeay, 

 in the Chevert, off Darnley Island, at 10 to 20 fathoms in sandy 

 mud. 



Family Echinometridzi. Gray, 1855. 



Test with an oblique axis, elongated or oblong, with more than 

 three pairs of pores to each arc. 



Genus 1. — Heterocentrotus. Brandt, 1835. 



Test very thick, elongated ; tubercles few, massive, smooth and 

 imperforate. Porif. zone very narrow above the ambitus, pores 

 on long narrow arcs of numerous pairs round the tubercles ; below 

 the zone widens much more than in Ecliinometra, becoming 

 broader than the I. space. Actinosome, very large, cuts slight. 

 Primary spines large, club-shaped, angular, twice the diam. of 

 test. Round the actinosome they are flattened ; auricles tall, 

 slender, with large opening, and connected by a low ridge. 



