132 PLATE LI. 



Fig. 6. One of the skeleton spicula. X 250 

 linear. 



A small piece of the dermal membrane of this species 

 is figured in Plate LXXVI, fig. 5. X 123 linear, in 

 contrast with the dermal membrane of I. Ingalli. 



ISODICTYA MAMMEATA, Bowerbank. 



Vol. ii, p. 306, ' Mon. Brit. Spongiadse.' 



Fig. 7.' Represents a specimen of the species from 

 the Diamond Ground, off Hastings. Natural size. 



Fig. 8. One of the skeleton spicula. X 250 

 linear. 



Fig. 9. A tension spiculum, from the interstitial 

 membranes. X 250 linear. 



ISODICTYA FALLAX, BowerbanJc. 



Vol. ii, p. 302, ' Mon. Brit. Spongiadas.' 



Fig. 10. -- Represents the type-specimen of the 

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



Fig, 11. A skeleton spiculum. X 250 linear. 



Fig. 12. One of the tension spicula, from the 

 dermal membrane. X 250 linear. 



Fig. 13. A tricurvate, acerate, tension spiculum, 

 from the dermal membrane. X 530 linear. 



