] 28 PLATE L. 



spiculum, from the interstitial membranes. X 250 

 linear. 



IsoDiCTTA juGOSA, Boiverhcmk. 



Vol. ii, p. 296, ' Mon. Brit. Spongiadje.' 



Fig. 11. — Represents tlie type-specimen of the 

 species from Shetland, in the calainet of the Rev. A. 

 M. Norman. Natural size. 



Fig. 12. — A skeleton spiculum. X 250 linear. 



Fig. 13. — One of the tension spicula, from the inter- 

 stitial memb]'ane. X 250 linear. 



Fig. 14. — A simple bihamate spiculum, from the 

 dermal membrane. X 5-30 linear. 



IsoDiGTYA Grbgorii, Bowerhaiik. 



Vol. ii, p. .301, ' Mon. Brit. Spongiads3.' 



Fig. 15. — Represents the type-specimen of the 

 species from the Moray Frith. Natural size. . The 

 sponge coats the inner surface of the shell for nearly 

 half the inner portion towards the hinge of the shell. 



Fig. 16.' — A skeleton spiculum of about the average 

 size. X 250 linear. 



Fig. 17. — One of the tension spicula of the inter- 

 stitial membranes. X 250 linear. 



IsoDiCTYA SIMPLEX, Boii:erJiank. 



Vol. ii, p. 294, ' Mon. Brit. Spongiadae.' 



For the figure of this species I must refer the reader 

 to Plate XLIV, fig. 6, of the present volume. 



Fig. 18. — Represents one of the skeleton spicula. 

 X 250 linear. 



In January, 1870, I received five specimens of 

 sponges for examination from the Rev. A. M. Norman, 

 who found them at low water mark in Stranrford 



