846 ADDENDUM TO THE MONOGRAPH OF THE AUSTRALIAN SPONGES, 



The oscula are small and circular, measuring about 1 mm. in 

 diameter, pretty numerous and scattered irregularly over the 

 surface. They are more numerous towards the interior than 

 towards the outer surface. 



Colour. 



Alive very light pink, nearly white ; in spirits this colour is 

 retained. Dry skeletons are grey in consequence of the prevalence 

 of sand. 



Canal System. 



A. Vestibule space. 



The vestibule space is developed as in Hahne tingens, 

 described in another paper of these Proceedings, and reminds 

 one of Hippospongia. There is no dermal lamella at all. The 

 lamellae terminate distally with sharp margins. An intei-- 

 esting structure is the cavity which pervades the whole of the 

 sponge. This has a width equal to a third of the diameter of the 

 whole sponge. It must be considered as the first step towards the 

 development of a pseudogaster, although it is divided from the 

 outer water only by the loose network described above. 



B. Canal system proper. 



The subdermal cavities are very extensive, and the canals in 

 the interior very large, many measuring 1 mm. in diameter. Tlie 

 ciliated chambers are very small and abundant. 



Skeleton. 



The network of horny fibres has very wide meshes; foreign bodies 

 are not very abundant and form the core only of the main fibres. 

 The main fibres have a thickness of 0.25 mm., the meshes an 

 average width of 0.9 mm., and the connecting fibres which are free 

 from foreign l^odies, measure 0.012 mm. in thickness. The fibres 

 are of a dark brown colour and consist of very uniform spongiolin, 

 which does not show any indication of being stratified. 



