PLATE XVIII. 



PsAMMOSPH.ERA. — SoROSPH^ERA.— SACCAMMINA. 



Diam. Page 



Figures 1-8. — Psammosphcerafasca, Schulze. .... 249 



Fig. 1. Large specimen, . . . . x 20 



Figs. 2, 3. Smaller examples, . . . x 40 



Fig. 4. Specimen built round a sponge-spicule, . x 40 



Fig. 5. Sessile specimen, . . . x 40 



Fi" 6. Test cut so as to show the interior, . x 40 



Fi". 7. Section of the wall, showing the fitting 



together of the sand-grains, . x 40 



Fig. 8. Specimens adherent to each other, . . x 40 



9, 10. — Sorosphcera confusa, Brady, 

 11-17. — Saccammiria sjiharica, M. Sars, . 



Figs. 11, 12. Lateral aspect; fig. 13, oral aspect. 



Fig. 14. Sessile specimen. 



Fig. 15. Test laid open to show the interior. 



Fig. 16. Polythalamous adherent specimen. 



Fig. 17. Fusiform specimen with two apertures, re- 

 sembling a segment of the Carboniferous 

 Saccammina earteri. 



18, 19. — Saccammina socialis, n. sp., 



15 251 



15 253 



•20 255 



