PLATE III. 



Spirastrella purpurea (Lmk.) Rdl. 

 (Photo's after the original specimens). 



Fig. i. S. E. 426 b. Side view. Natural size. 



Fig. 2. S. E. 1945. Coralline alga almost entirely covered by Spirastrella; in some parts the sponge again 



covered by fragments of shells etc. Natural size. 

 Fig. 3. B.M. 10. Spirastrella cunctatrix. Crtr. After a dry specimen. Natural size. 

 Fig. 4. B. M. 2. Spirastrella areolata Dy. After the dry type-specimen. Natural size. 



Fig. 5. S. E. 92 c. Side view. Natural size. 



