On Sponges from South Australia. 369 



XXXVII. — Sup]L)lement to the Descriptions of Mr. J. Brace- 

 bridge Wilson''s Australian Sponges. By H. J. Carter, 

 F.R.S.&C. 



[Plate X.] 



[Continued from p. 290.] 



Order III. PSAMMONEMATA. 



Stelospongos, Sdt. 



I have already gone into the history of this genus under the 

 head oi^^ Stelospongus la^vis^ Hyatt " (' Annals/ 1885, vol. xv. 

 p. 303), and I should not have returned to the subject had I 

 not found, on comparing the whole of the specimens in 

 Mr. Wilson's several collections, that I had confused, in 

 my description, two forms so very much alike externally that 

 without many examples of each, and thus sufficient material 

 for the destruction caused by sectioning, I should not have 

 been able to contrast their characters satisfactorily for dis- 

 tinction. Let us now see what these are. 



In Stelospongus Icevis the keratose skeletal structure not 

 only predominates in quantity over the sarcodic, but is pecu- 

 liarly abundant, presenting in a vertical section of the dried 

 and washed-out specimen a radio-Horal arrangement of the 

 main bundles of the fibre, by their curving upwards and 

 outwards from the lower part of the axis to the circumference, 

 being bound together on their way by a dense network of 

 lateral or smaller fibre. In the other species, for which I 

 propose the name of '"'' Stelospongus crihrocrusta^'' it is the 

 opposite, viz. the sarcodic greatly predominates over the kera- 

 tose structure, which^ on the other hand, is very scanty, 

 presenting itself only under the form of a scattered fibro- 

 reticulation, in which the meshes appear from their width to 

 be almost absent in the centre, while they thicken by becoming- 

 smaller towards the circumference, and especially in the 

 stem, where this structure is most required for general 

 support. 



In Stelospongus hevis the surface consists of a thin incrus- 

 tation uniformly studded over with little tufts of fibres, which 

 project beyond the dermal sarcode and are the circumferential 

 terminations of the radiating bundles of the intei'ior; these 

 tufts may be separate, or, becoming compressed and extended 

 laterally, so as to meet each other, may give rise to a poly- 



