PLATE XXI LI. 
Pseudohornera diffusa (Hall). (Pago 50.) 
[See also PI. XVIII, figs. 6-9.] 
Fio. 1. Transverse section of a branch, X 18, showing central lamina. 
2. Tangential section, X 18. 
3. Vertical section, X 18, showing thick basal plate, the form of the zooecia, and 
the abortive cells beneath the central lamina. 
Rochester shale, Lockport, N. Y. 
Diploclema sparsum (Hall). (Page 17.) 
[See also PI. V, figs, (i, 7.] 
4. Tangential seel ion, X 18, cutting the zooecia at varying levels between the aper- 
t ures and the median line. 
5, 6. Two transverse sections, X 30, showing the central lamina. 
Rochester shale, Lockport, N. Y. 
Rhinopora verrucosa Hall. ( Introduced for comparison,) 
7. Fragment, natural size, showing the covered canals. 
5. A fragment in which the canals are apparently absent. This specimen closely 
resembles the zoarium of Rhinopora curvata. 
9. Enlargement of (ig. 8, showing the arrangement of the zcxpeia. 
Clinton formation, Flamborough Head, Canada. 
Codoclema cavernosa n. sp. (Page 21.) 
10. A zoarium, X 1.5, showing the utricular form of growth. 
1 1 . A still further enlargement of the same specimen, exhibiting the arrangement of 
the zooecia. 
12. A vertical set ion, X 20, through one of the sides of the zoarium. 
13. Tangential section, X 20. 
Rochester shale, Lockport, N. Y. 
Fistulipora tuberculosa Hall. (Page 23.) 
[See also PI. VII, figs. 11-15; PI. VIII, figs. 7, 8.] 
14. A characteristic specimen, X 2, showing the usual utricular method of growth. 
Rochester shale, Lockport, N. Y. 
Fistidipora crust ida n. sp. (Page 24.) 
[.see also PI. VII, Tigs. 7-10; PI. VIII, figs. 16, 17.] 
15. A zoarium, X 2. 
Rochester shale, Lockport, N. Y. 
Trematopora whitfieldi Ulrich. (Page 44.) 
[See also PL XXVII, figs. 16, 17.] 
16. A fragment, natural size. 
17. Surface of same, X 18. 
Waldron shall , Waldron, Ind. 
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