PLATE XLV. 113 



Fig 24. One of the bidentate, equi-anchorate, 

 retentive spicula. X 530 linear. 



HALICHONDRIA NIGRICANS, Bowerbank. 



Vol. ii, p. 266, ' Mon. Brit. Spongiadse.' 



Fig. 25. Represents the type-specimen received 

 from Mr. McAndrew. Natural size. 



Fig. 26. One of the terminally spined, subfusiform, 

 cylindrical spicula, from the dermal membrane. 

 X 250 linear. 



Fig. 27. A palmato-inequi-anchorate spiculum, from 

 the dermal membrane. X 530 linear. 



Fig. 28. A dentato-inequi-anchorate spiculum, from 

 the dermal membrane. X 530 linear. 



Figs. 29 and 30. Two of the inequi-bipocillated 

 spicula, from the interstitial membranes. X 530 

 linear. 



Fig. 31. An acuate, entirely but minutely spined, 

 skeleton spiculum. X 250 linear. 



HYMENIACIDON VARIANTIA, Bowerbank. 



Vol. ii, p. 174, ' Mon. Brit. Spongiadse.' 



Fig. 32. A skeleton spiculum of Hymeniacidon 

 variantia, of the normal form and of the largest size. 

 X 123 linear. 



Fig. 33. A smaller sized skeleton spiculum of the 

 same species, exhibiting one of the common forms of 

 contortion, which prevails among the smaller sized 

 skeleton spicula. X 123 linear. 



Fig. 34. Represents a small portion of the dermal 

 membrane, with its spicula in situ, with loosely fascicu- 

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

 and small bihamate retentive spicula irregularly dis- 

 persed, X 320 linear. 



8 



