OF NEW SOUTH WALES. 171 



Peronella decagonalis. Lesson. 



Test large and graceful, much flattened, edges scarcely swollen, 

 central part rising abruptly, but slightly from end of petals ; 

 shape, regularly decagonal. Petals narrow, porif. furrows closely 

 packed ; zones converging slightly towards extremity, and not 

 rounded along sides of petals. Actinal surface flat. Actinosome 

 round, central, with furrows extending nearly to the edge ; anus 

 elliptical near edge, but oblique to the longitudinal axis. Tuber- 

 culation uniform on both surfaces, but larger on lower. Color 

 variable, but red when living. Port Jackson and along the east 

 coast. Long diam. from 50 to 120 mil. 



Peronella orbicularis. — Much smaller than the last ; more 

 rounded with shorter petals, and more swollen edge. Supposed 

 by Agassiz to be the young of P. decagonalis. Diam., 26. Same 

 localities. 



Peronella peronii, Agass. Four G. openings in A. spaces a 

 considerable distance from apex. Outline circular, edge swollen 

 slightly, petals bfoadly lanceolate ; mouth transversely elliptical. 

 A. furrows indistinct, short. Long, 26. Tasmania, Jervis and 

 Twofold Bays, Port Jackson, Broken Bay. 



Family Scutellim:. Agassiz, 1841. 



Extremely flat, circular urchins, perforated or cut at the margin. 

 A. furrows spreading, branching, and anastamosing. Partitions 

 radiating from single points. Tubercles of upper and lower 

 surface differing greatly in size. 



Echinarachnius parma. Lamarck. 



A common rounded form, with indentations on the edge, which 

 is found almost all over the world. Common on the east coast. 

 Many specimens collected by the " Chevert" Expedition within 

 the tropics. It is also common at Guichen Bay on the S. coast 

 and along the coasts of Victoria. 



Genus 2. — Arachnoides, Klein, 1734. 



Circular urchins depressed, but conical. Ambulacral furrows, 

 simple. Partitions of interior by pillars, numerous, slender, 



