O C) r» 



PLATE XC. 



RArillODESMA SIMPLISSIMA, BoiVcdxill.lc. 



Fig. 1. — Eepresents the type-specimen. Natural 

 size. 



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

 dermal membrane. X 250 linear. 



Fig. 3. — A skeleton spicnlum. X 250 linear. 



IsuDiCTYA DuiJiA, Bowerhank. 



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, {n, a, n, a, a) ])ortions 

 of the sponge ; {h, h) Ascidian ; [c) a part of the inner 

 surface of the shell. 



Fig. 6. — An acerate spiculum from the dermal mem- 

 brane. X 250 linear. 



Fig. G. — 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. 



Desmaoidon ROTALis, Bovjerhanh. 



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 Ijalsaiu. X 3G linear. 



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

 right angles to its dermal surface, showing the mode of 



