1848.] LONSDALE ON FOSSIL ZOOPHYTES. 103 



Plate V. 



Fig. 16. Siphodictyum gracile. General plan of growth, nat. size. 



17. Front of a branch. Fig. 17 to 23 mag. 7 diam. 



18. Front of another branch, traversed by fine longitudinal lines. 



19. Reverse surface. 



20. Vertical section through the centre. 



21. Transverse section. 



22. Slightly worn down front. 



23. Slightly worn down reverse side. 



24. Chistna furcillatum. General plan of branching, nat. size. 



25. Nearly perfect exterior, mag. 7 diam. 



26. Vertical section. The position of the mouth to the tube is indicated in 

 some cases, as near x, by a small projection ; and the interval between 

 the tubes by the little space immediately above the projection : mag. 7 

 diam. 



27. A section nearer the original surface, mag. 4 diam, : the character of the 

 intervals between the tubes is shown in the portion greatly enlarged. 



2S. Transverse section, mag. 7 diam. 



