Plate 23. 
Figs. 1-3. Porella ( Palmicellaria ) convoluta Ulrich and Bassler, 1904. (p. 150.) 
1. The convoluted, bifoliate zoarium, natural size. 
2. Zooecia, X 20, showing the prominent mucro and the avicularium. 
3. Surface of another fragment, X 20, with several closed zooecia. 
Miocene (Calvert formation): Reeds, Maryland. 
Fig. 4. Porella ( Palmicellaria ) punctata Ulrich and Bassler, 1904. (p. 150.) 
The bifoliate type specimen, X 20. 
Miocene (Calvert formation): Reeds, Maryland. 
Figs. 5-10. Porella reversa Ulrich and Bassler, 1904. (p. 148.) 
5. Portion of the iucrusting zoarium, X 20, showing the zooecia with thin raised borders. 
6. Another zoarium, X 20, with ovicelled zooecia. 
7. Drawing showing usual aspect of the ovicelled and unovicelled zooecia, X 28.5. 
8. Zooecia of a specimen with ovicells, X 28.5. 
9. Several zooecia, X 28.5, with the boundaries well defined. 
Miocene (St. Mary’s formation): Cove Point, Maryland. 
10. A view of the zooecial walls after abrasion of the frontal, X 20. 
Miocene: Kuhns, Carteret County, North Carolina. 
Figs. 11-17. Retepora doverensis Ulrich and Bassler, 1904. (p. 152) 
11-13. Three specimens, natural size. 
14. Portion of a type specimen, X 20, showing the fissured ovicell and the wide irregular rimule 
spiramen. 
15. Noncelluliferous side of a zoarium, X 20. 
16. One of the original types, X 8, with ovicelled zooecia. 
17. Drawing of several zooecia, X 30. 
Miocene (Choptank formation): Dover Bridge, Maryland. 
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