13 



IG 



EEY TO THE AUSTRALIAN GENERA. 241 



'' Supporting - spicules tetract and monact. 



(Tetraxouia.) 13 



(7) ^ Supporting - spicules exclusively monact. 



(Monaxouia.) (14), p. 242. 



^ No supportiug-spicules. (Oligosilicina.). . . . (15), p. 242. 



{Spicules irregular, articulating. (Lithistida?.) 

 Spicules regular, not articulating 16 



r Supporting-spicules tetract and monact .... 17 

 [ Supporting-spicules chiefly monact (18) 



With spherical spicules (sterrasters) in the 

 cortex. (GeodidsD.) 19 



Without spherical spicules (sterrasters), with 

 stellates or small rod-shaped microsclera. 

 1'' < (Stellettidffi.) (20) 



Without microsclera. (Aucorinidre.) (21) 



With sigmate, spiral, or rod-shaped micro- 

 I, sclera. (Tetillid^.) (22) 



^ Oscula in a group at the bottom of a depres- 

 sion ; ectochonas shallow Geodia, p. 33. 



19 Oscula scattered ; ectochonse deep Isops, p. 34. 



Oscula similar to the inhalant pores ; with re- 

 curved spicules, ejected on touch, on the 

 surface Cydonium, p. 36. 



f With stellate microsclera ; without sand .... Stelletta, p. 37. 



With sand in the cortex Psammastra, p. 38. 



(20) «< 

 Without stellates or sand, with rod-shaped 



microsclera inserted perpendicularly in the 



surface Thalassomora, p. 40. 



(21) With cortex Ancorina, p. 41. 



(22) With abundant, small, spiral microsclera. . . . Spiretta, p. 42. 

 (18) Without microsclera Tethyopsilla, p. 45. 



