PLATE XII. 
Eridotrypa spinosa n. sp. (Page 29.) 
[See also PI. XXV, fig. 15.] 
Fig. 1. Vertical section, X 20, showing the tabulation and the thick zocecial walls of th« 
mature region. 
2, 3. Two portions of a tangential section, X 20, exhibiting the thick zocecial wells 
huge numerous acanthopores, and the variation in the number of mesopores. 
Rochester shale, Grimsby, Ontario. 
Eridotrypa striata (Hall). (Page 32.) 
[See also PL XXIV, figs. 3-6; PL XXV, fig. 14.] 
4. Vertical section. X 20, showing the characteristic tabulation and the slight. thick4 
cuing Of 1 he walls in the mature region. 
5, 6. Portions of two tangential sections, X 20, showing the appearance of the youthfu 
and aged condil ions, respectively, of the mature region. 
Rochester shale, Lockport, N. Y. 
Eridotrypa solida ( Hall). ( Page 30.) 
[See also Pi. XXIV, figs. 20 23; PL XXV, fig. 16.] 
7. yertical section, X 20, showing the usual absence of diaphragms and slight thick- 
ening of walls in the ma lure region. 
8, 9. Two portions of a tangential section, X 20, showing the angular zocecia and meso- 
pores of the mature /.one. 
Rochestei shale, Lockport, N. Y. 
Eridotrypa similis n. sp. (Page 31.) 
[See also PL XXVI, figs. 1, 2.J 
10. A tangential section, X 20, with the usual thick-walled angular zocecia and meso- 
pores and characteristic acanthopores. 
11. Vertical section, X 20, exhibiting few diaphragms in the zocecial tubes and more 
numerous ones in the mesopores. 
12. A tangential section, X 30, passing through a macula. 
13. Another tangential section showing more numerous acanthopores and mesopores 
than usual. 
14. Surface of one of the figured types, X 8. 
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