PLATE IX. 



ISODICTYA SCITULA, 



Figs. 1, 2 and 3. Specimens of the sponge growing 

 on Nullipora polymorplia. Natural size. 



For figures of the spicula of this sponge see 

 Plate IV, figs. 13. 



ISODICTYA PERPLEXA, BowerbanJc. 



Figs. 4< and 5. Represent the type specimens of the 

 sponge coating Nullipora polymorpha of the natural 

 size. 



Fig. 6. A portion of the dermal membrane. 



Fig. 7. One of the long fusiformi-acerate spicules 

 of the skeleton. 



