3 



Plate 11. 

 Nicholsonella gibbosa (Eichwald). 



Figs. 1-5. Five zooecia of various sizes and shapes, X 1-5. 

 6. Surface of the original of fig. 1, X 18. 



Glauconite limestone (B2), Wassilkowa, government of St. Petersburg. 



Dittopora colliculata (Eichwald). 



7-10. Four small examples, natural size, with distinctly elevated maculae. 

 11-14. Four specimens of the usual size and surface features. 

 15. A nearly smooth example, natural size. 



Wassalem beds (D3), Uxnorm, Esthonia. 



Dittopora annulata (Eichwald). 



16. Portion of a zoarium, X 1-5, with indistinct maculse. 

 Orthoceras limestone (B3), island of Rogo, Esthonia. 



17. An example, Xl.5, preserving the parasitic basal portion, and showing 



distinct ring-like maculae. 

 Glauconite limestone (B2), Tswos, on the Wolchow River, government 

 of St. Petersbiu-g. 



Dittopora davaeformis (Dybowski). 



18-23. A group of specimens, X2, exhibiting various forms of growth. 



24. Fragment of a brachiopod,Xl.5, with the basal portions of two examples 



attached. 

 Glauconite limestone (B2), Tswos and other localities, government of 

 St. Petersburg. 



Trematopora cystata, new species. 



25. Surface of a well-preserved example, X15. 

 Kuckers shale (C2), Reval, Esthonia. 



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