HJEODIA.. 33 



2. Group CHORISTIDA. 

 ChoiidrospoiigiaB with tetraxon spicules of regular shape. 



Tribus Tetradina. 



The chief spicules are tetracts with equal rays, and can- 

 clelabras. 



No specimens in tke Australian Museum. 



Tribus Trianina. 



The centres of the tetract spicules with one differentiated ray 

 lie in the surface, in which the equal rays extend tangeutially. 



^amilia GEODID^. 



Trianuia with a cortex of globostellate spicules. The body 

 is spherical or irregularly massive and branched. In most forms, 

 particularly the regular ones, the supporting skeleton exhibits a 

 regulai: radial structure. Large monaxon and tetraxon megasclera 

 and stellate microsclera are observed. Chouse, which can be 

 closed by a muscular sphincter, are present. 



Genus GEODIA. 



The oscula situated in groups at the base of a common de- 

 pression, which forms, when highly developed, a praeosculum. 

 Ectochonse not much depressed, nearly cup-shaped. Body often 

 spherical, sometimes also massive or branched. 



Geodia nigraj n. sp. 



Massive, lobose sponges which are attached by a broad base. The spherical 

 v^pecimens have a diameter of 30-40 miUim. ; the lobose forms appear as four 



