223 



PLATE LXXVI. 



IsoDiCTYA OBSCURA, Bowerbauh. 



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

 Diamond Ground off Hastings. Natural size. The 

 dark parts opposite (a a) exhibit the surface of the 

 sponge ; the lighter parts covering the type-specimen 

 are Hymeniacidon lactea. 



Fig. 2. — One of the skeleton spicula. x 250 

 linear. 



IsoDiCTYA IMITATA, Boiverhanlc. 



Fig. 3. — Represents the type-specimen. Natiu^al 

 size. 



Fig. 4. — An average-sized skeleton spiculum. 

 X 2-50 linear. 



Fig. 6. — One of the bidentate, equi-anchorate, re- 

 tentive spicula from the dermal membrane. X 530 

 linear. 



Fig. 6. — One of the minute, palmato-inequi-anchorate, 

 retentive spicula from the dermal membrane. X 630 

 linear. 



IsoDiCTYA cOElAOEAj BoiverbanJc. 



Fig. 7. — Represents the type-specimen in the cabinet 

 of the Rev. A. M. Norman. Natui'al size. 



Fig. 8. — One of the sub-fusiformi attenuato-acuate 

 defensive spicula of the porous areas. X 250 linear. 



Fig. 9. — A tricurvate, cylindrical, tension spiculum. 

 X 530 linear. 



Fig. 10. — One of the equi-anchorate, bidentate, re- 

 tentive spicula. X 530 linear; 



