168 THE PROCEEDINGS OF THE LINNEAN SOCIETY 



Sub-Order 2. — Clypeastril\e, Agass., 1836. 

 Urchins generally depressed, scutiforura, with petaloid ambu- 

 lacra, anal and apical system separate. Spines somewhat 

 resembling regular Echini. Ambulacral pores of petals passing 

 between the plates, and the ambulacral system greatly developed. 

 Lines of minute pores extend at right angles to the general 

 course of the porif. zone. Actinal surface with ambulacral fur- 

 rows irregularily crowded with pores, the furrows terminating in 

 the actinosome. Plates round, actinosome cuneiform, forming a 

 buccal rosette. A. broader than I. Tubercles small, crenulate, 

 and perforate. Teeth simple, articulating on the auricles, with- 

 out the muscular system of Desmosticha. 



Family Eucltpeastridj:, Hagckel, 1866. 

 Test with simple supports, connecting the upper and lower 

 floors, and covered with spines of a uniform structure. The 

 supports are either internal pillars, needles, or radiating par- 

 titions. 



Sub-Family Fibularina, Gray, 1855. 



Small, globular, petals rudimentary, simple partitions radiating 

 from the periphery to the actinosome. 



Genus Fibularia, Lamk., 1816. 

 Ovoid, flattened anteriorly, partitions absent. Petals rudimen- 

 tary imperfectly petaloid, not closing, diverging pores not 

 congregated, few. Actinosome central, anus nearer to it than the 



edge. 



Fibularia australis, Desmoulins. 



A large ovoid species, measuring 20 mil., with large pentagonal 

 mouth and large elliptical anal opening. I have never seen a 

 specimen. 



Fibula volva, Agass. 



A very small elongate species, pointed at both ends, with 

 mouth and anus round, close together, and small, the latter 

 especially so. One specimen dredged by the Cheverfc at Bet 

 Island, Torres Straits. 



