142 PLATE LVI. 



ISODICTYA CLATCKEI, BowerdanJc. 



Vol. ii, p. 330, ' Mon. Brit. Spongiadae.' 



Fig. 11. Represents two specimens of the species 

 on the stem of a slender sertularia, from North Shields, 

 by Dr. "W. B. Clarke. Natural size. 



Fig. 12. Another specimen from the same locality, 

 parasitical on a different species of sertularia. Natural 

 size. 



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

 stitial membranes. X 250 linear. 



Fig. 14. A dentato-inequi-anchorate, retentive spicu- 

 lum from the dermal membranes. X 530 linear. 



Fig. 15. A skeleton spiculum. X 250 linear. 



Another specimen of this sponge is represented in 

 Plate XLIX of the present volume, at the basal portion 

 of figure 6 at b b. The specimen of sertularia on 

 which it is parasitical was collected by Mr. Gardener, 

 at Dundee, and it now forms part of the Johnstonian 

 collection of British sponges in the British Museum. 



ISODICTYA FUCOEUM, Bower&ank. 



Vol. ii, p. 322, ' Mon. Brit. Spongiadse.' 



Fig. 16. Represents a fine specimen of the species 

 found by the late Mr. Thomas Ingall at Shoreham, 

 near Brighton. Natural size. 



Fig. 17. A slender tension spiculum, from the 

 dermal membrane. X 250 linear. 



Fig. 18. One of the skeleton spicula. X 250 

 linear. 



Fig. 19. An inequi-palmato-anchorate retentive 

 spiculum. X 530 linear. 



Very few of these spicula are found among the 

 simple bihamate ones of the dermal membrane. 



The specimen represented by figure 16 is unusually 

 free from the entanglements of the stems of the fucus 



