PLATE XXXIII. 85 



Fig. 32. A skeleton spiculum of the^ normal form 

 and of the largest size. X 123 linear. 



Fig. 33. A smaller sized skeleton spiculum, exhibit- 

 ing one of the very common forms of contorsion, 

 which prevails among the smaller skeleton spicula. 

 123 linear. 



Fig. 34. Eepresents a small portion of the dermal 

 membrane with its spicula in sit/I with loosely fascicu- 

 lated, minute, acuate, tension, spicula, and the large 

 and small bihamate, retentive spicula, irregularly 

 dispersed. X 320 linear. 



HYMENIACIDON FALLAX, Bowerbank. 



Vol. ii, p. 177, ' Mori. Brit. SpongiacLe.' 



Fig, 15. Represents the type specimen of the 

 species which I received from Mrs. Griffiths. Natural 

 size. 



Fig. 16. One of the spicula of the dermal mem- 

 brane. X 150 linear. 



Fig. 17. A skeleton spiculum. X 150 linear. 



Fig. 18. One of the slender," flexuous, tension spi- 

 cula of the interstitial membranes. X 150 linear. 



HYMENIACIDON VIRIDANS, Bowerbank. 



Yol. ii, p. 178, 'Mon. Brit. Spougiadse.' 



Fig. 19. Represents the type-specimen of the 

 species in the Cabinet of the Rev. A. M. Norman. 

 Natural size. 



Fig. 20. A specimen of the same species and from 

 the same locality, for which I am indebted to Mr. 

 Norman. Natural size. 



Since the description of the type-specimen in vol. ii, 

 p. 178, I have had the opportunity of examining 

 several other specimens of the species. They appear 

 to vary to a very considerable extent in size, form, and 



