880 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1920. 



Figs. 13-15. — Tergopores. 13. Longitudinal thin section of Pleuronea sub- 

 pert usa Canu and Bassler from the Eocene of Mississippi, x 12, illustrating the 

 structure of the tergopores (to the right) and the zooecial tubes. 14. Lateral 

 side of the zoarium, x 6, showing oblique arrangement of the apertures. 15. 

 Dorsal side of the zoarium, x 6, illustrating the large tergopores. 



Figs. 16-1S. — Vacuoles. 16. Dorsal side, x 12, of Hornera frondiculata La- 

 mouroux showing the vacuoles at the base of longitudinal sulci. 17. Celluliferous 

 side of the same species, x 12. 18. Longitudinal thin section, x 12, of Hornera 

 cmtarctica Waters showing vacuoles on both the frontal (to the left) and 

 dorsal sides. 



Figs. 19-21. — Cancelli. 19. An ovicelled specimen of Lichenopora radiata 

 Audouin, x 12, showing the zooecial apertures in v^jular rows separated by the 

 cancelli. 20. Longitudinal thin section, x 12, of Lichenopora goldfussi Ruess. 

 The cancelli are the superposed and ramified tubes. 21. Portion of a zoarium of 

 Lichenopora holdsivorthi Busk, x 12, illustrating the spinules in the cancelli. 



Figs. 22-24. — Dactylethrae. 22. Dorsal side of a branch, x 12, of Erkosonea 

 ad mot a Canu and Bassler, from the Eocene (Jacksonian) of North Carolina 

 exhibiting the dactylethrae. 23. A longitudinal thin section of Erkosonea 

 semota Canu and Bassler, x 12, showing zooecial tubes to the left and dactyle- 

 thrae to the right. 24. Celluliferous side of E. admota Canu and Bassler, x 12. 



Figs. 25-27. — Firmatopores. 25. Lateral view of a branch of Idmidronea 

 culter Canu and Bassler, x 6, from the Eocene (Jacksonian) of North Carolina 

 showing the openings of the zooecial tubes in the upper right hand corner and 

 the remainder of the branch covered with firmatopores. 26. Longitudinal thin 

 section, x 12, of J. coronopus Milne-Edwards, illustrating structure of firmato- 

 pores (to the right) and zooecial tubes. 27. Celluliferous surface of I. rosacea 

 Canu and Bassler, x 12, from the Eocene (Jacksonian) of North Carolina, ex- 

 hibiting the zooecial apertures and the firmatopores. 



Figs. 28-29. — Nematopores. 28. Longitudinal thin section, x 12, of Diplo- 

 desmopora opposita Canu and Bassler, from the Cretaceous rocks of France 

 showing the zooecial tubes to the right and nematopores to the left. 29. An 

 ovicelled branch of the same species, x 6, showing lateral position of the ovicell 

 and the nematopores on the basal (right) side. 



Figs. 30-31. — Mesopores. 30. Longitudinal thin section of Tretocycloecia 

 reticulata Canu and Bassler, x 6, showing the formation of the numerous 

 mesopores in this species. 31. A zoarium of this species, x 6, from the Eocene 

 (Jacksonian) of South Carolina illustrating the resemblance at the surface be- 

 tween the zooecia and mesopores. 



