PLATE LV1II. 149 



ISODICTYA GRACILIS, Bowerbank. 



Vol. ii, p. 331, ' Mon. Brit. Spongiadae.' 



Fig. 23. Represents the type-specimen of the 

 species. Natural size. 



Fig. 24. One of the skeleton spicula. X 250 

 linear. 



Fig. 25. An acuate, slender, tension spiculum 

 from the interstitial membranes. X 250 linear. 



Fig. 26. - - One of the minute, bidentate, equi- 

 anchorate, retentive spicula from the interstitial mem- 

 branes. X 430 linear. 



ISODICTYA LUEIDA, BowerbanL 



Vol. ii, p. 336, ' Mon. Brit. Spongiadse.' 



Fig. 27. Represents a small specimen of the species 

 in a fine state of preservation, from Dunstanborough. 

 In. the cabinet of the Rev. A. M. Norman. Natural 

 size. 



Fig. 28. A tension spiculum from the dermal 

 membrane, submucronate at one termination. X 250 

 linear. 



Fig. 29. A tension spiculum from the dermal mem- 

 brane, with hastate terminations. X 250 linear. 



Fig. 30. One of the long, slender, acuate, tension 

 spicula. X 250 linear. 



Fig. 31. A skeleton spiculum, basally and apically 

 spined. X 250 linear. 



Fig. 32. A tridentate, equi-anchorate, retentive 

 spiculum from the interstitial membranes. X 530 

 linear. 



The spicula of this description are frequently biden- 

 tate only. 



