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 MAJiMEATA, Bovjerhaiih. 



ToL ii, p. 306, ' Mon. Brit. SpongiadEe.' 



Fig. 7.- — Eepresents a specimen of the species from 

 the Diamond Groimd, ofi" 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. 



IsODiCTTA PALLAx, Bouwrhank. 



Yol. ii, p. 302, ' Mon. Brit. Spongiadse.' 



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 hnear. 



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. 



