142 PLATE LVI. 



IsoDiCTYA Clakkei, Boverbonh. 



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



Fig\ 11. — Represents two specimens of the species 

 on tlie stem of a slender sertularia, from Nortli 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 h h. 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 FUCORUM, Bowevbank. 



Vol. ij, p. 322. ' Mon. Brit. Spongiada\' 



Fig. 16. — Represents a fine specimen of the species 

 found by the late Mr. Thomas Ingall at iShoreham, 

 near Brighton. Natural size. 



Y\g. 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 1 6 is unusually 

 free from the entanglements of tlie stems of the fucus 



