PLATE X 



Page 

 Figs 1 to 4. Pachydictta pumila Ulr , 15' 



I. A group of specimens of the natural size. 



2 and 3. Two fragments, natural size and X9, with some of the zooecial apertures closed. 

 4. The basal part of a rather young example, natural size and x9. (See also plate, VIII). 

 Upper part of the Galena shales, near Cannon Falls, Minn. 



Figs. 5 to 10. Pachtdictya foliata Ulr. 14! 



5 to 8. Four specimens of the natural size. Fig. 6 presents the unusual condition of raised 

 maculae. 



9. Surface of fully matured example, xg. 



10. Surface of a young zoarium, xi8. (See also plate IX). 



Figs. 11 to 14. Pachtdictya teiserialis Ulr 15! 



II. Portion of a block of limestone with a group of the slender ramulets of this species, 



natural size. 



12. Surface of an old exaciple, xl8, on which many of the zocecial apertures preserve the 

 closures. 



13 and 14. Two transverse sections. X25, the first prepared from a young example, the sec- 

 ond from one like the original of fig. 12. 

 Trenton limestone, Montreal, Can. 



Figs. 15 to 20. Tbigonodictya conciliatrix Ulr 1& 



15 to 1 9. Five specimens of the natural size, illustrating the zoarial variability of the species. 



20. Surface of well preserved example x9. (See also plate IX.) 

 Upper third of the Trenton shales near Cannon Falls, Minn. 



Figs. 21 to 25. Stictopoeblla cribrosa Ulr 18 



21. Nearly complete zoarium of the prevailing type of this species, natural size. 



22. A thin fragment less regularly developed than usual. 



23. Surface of an excellently preserved example, xg. 



24. Another portion of same xi8. In this specimen the mesopores are very numerous. 



25. Tangential section of an average specimen, xi8. In the upper part of the figure the 



section descends to the level of the prostrate portion of the zooecial tubes. (See also 

 plate XI.) 

 Middle third of the Trenton shales at Minneapolis. 



