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PLATE XC. 

 RAPHIODESMA SIMPLISSIMA, Bowerbank. 



Fig. 1. Represents the type-specimen. Natural 

 size. 



Fig. 2. One of the slender acuate spicula from the 

 dermal membrane. X 250 linear. 



Fig. 3. A skeleton spiculuin. X 250 linear. 



ISODICTYA DUUJA, BowerbanJc. 



Fig. 4. Represents the type-specimen dispersed on 

 the surface of a large dried Ascidian, based on a valve 

 of a dead shell. Natural size. (, ft, a, a, a) portions 

 of the sponge ; (b, b) Ascidian ; (c) a part of the inner 

 surface of the shell. 



Fig. 5. An acerate spiculum from the dermal mem- 

 brane. X 250 linear. 



Fig. 6. One of the acuate skeleton spicula. X 250 

 linear. 



Fig. 7. One of the bidentate, equi-auchorate, re- 

 tentive spicula from the dermal membrane. X 530 

 linear. 



DESMACIDON BOTALIS, Bowerbank. 



Fig. 8. Represents the type-specimen parasitical on 

 a sertularia. Natural size. 



Fig. 9. A small piece of the dermal membrane with. 

 its hexradiate confluent rotulate areas, mounted in 

 Canada balsam. X 36 linear. 



Fig. 10. A section of a portion of the sponge at 

 right angles to its dermal surface, showing the mode of 



