

I 









* 



Plate 18. 



Fig. 1. Gellius perforatas. Upper surface; from a photograph ; {. 



a 



a 



tt 



tt 



it 



a 



tt 



tt 



u 



2. Oceanapia bacillifera. Fistula; from a photograph ; \. 



3. Hymeraphia, sp. incrusting Oceanapia bacillifera. Spicules ; x 450. 



4. Oceanapia bacillifera. Tangential section through wall of fistula, showing 



m arrangement of skeletal spicules and spongin. Meshes 



in the skeletal framework, which in the figure are 

 represented as vacant, are filled with parenchyma; x 70. 



5. Tylodesma alba. Megascleres ; x 70. 

 6. 

 7. 



: h « 



<■<■ 



tt 



tt 



it 



Sigmata ; x 450. 



From a photograph. Sponge viewed obliquely from the side, 

 so that upper surface is seen ; {. 



8. Tylodesma vestibularis. Megascleres ; x 70. 



9. 



« 



it 



Sigmata ; x 450. 



10. Phakellia lamelligera. Outer surface of skeletal framework. Piece has been 



macerated in potash. From a photograph ; x 5. 







I 



: 

 1 



B 



