PLATE X. 
Mesotrypa nummiformis (Hall). (Page 27.) 
Figs. 1, 2. Tangential and vertical sections, respectively, X 20. 
3. Top and edge views of specimens, natural size, to show the characteristic growth. 
4. Surface of the original of fig. 3, X 8. 
Rochester shale, Lockport, N. Y. 
Orbignyella expansa (Ringueberg). (Page 26.) 
5. Vertical section, X 20, of a typical example with the usual development of 
curved diaphragms. 
6. Tangential section, X 20, through the mature region, exhibiting the large 
zooecia of a portion of a macula, and the smaller intermacular zocacia. 
7. Several intermacular zooecia, X 30, with the characteristic wall structure well 
developed. 
8. Surface of Ringueberg's type, X 8. 
Rochester shale, Lockport, X. Y. 
Orbignyella magnopora n. sp. (Page 27.) 
9,10. Vertical and tangential sections, X 20, exhibiting the comparatively few 
curved diaphragms and the large, thin-walled zooecia characteristic of the 
species. 
11. Several zooecia of a tangential section, X 20, giving the appearance when the 
curved diaphragms are cut. 
12. Surface of type specimen, X 8, exhibiting the large, thin-walled zooecia by 
which externally the species can l>e separated from the associated 0. expansa. 
Rochester shale, Grimsby, Ontario. 
Rhombotrypa spinulifera n. sp. (Page 37.) 
[See also PI. XXV, f.g. 21.] 
13. Vertical section, X 20, exhibiting the zones caused by the turning of the 
zooecia at regular intervals. 
14. Tangential section, X 20, cutting the mature region where the mesopores 
are well developed. 
15. A few zooecia and mesopores, X 35, of a section passing through the most mature 
portion of the zoarium and showing the acanthopores distinguishing this 
from other species of the genus. 
16. A portion of a transverse section, X 20, exhibiting the quadrate shape of the 
zooecia in the immature zone. 
Rochester shale, Lockport, N. Y. 
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