PLATE Lvin. 149 



IsoDiOTYA GRACILIS, Boiverhcmk. 



VoL ii, p. 331, ' Mon. Brit. SpongiadiB.' 



Fig. 23. — Repi-esents 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. 



IsoDiCTTA LUKiDA, Bowerhank. 



Vol. ii, x). 336, ' Mon. Brit. Spongiadse.' 



Fig. 27. — Represents a small specimen of the species 

 m 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 260 

 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 580 

 linear. 



The spicula of this description are frequently biden- 

 tate only. 



