PLATE VIII. 



Page. 



Figs. lto3. Rhinidictya mutabilis Ulr -• = 125 



Three portions of an old example of ttiis species X9, showing, in 1, the thick, rounded 

 and granulose margin, In 2, the shape of the zooecial apertures at the upper extremity 

 of the specimen, and in 3, their form near the lower end of same. (See also plates 

 VI and VII.) 



Figs. 4 and 5. Pachydictta ptjmila Ulr 15'' 



Two fragments of the natural size, and one of them representing the basal part of the 

 zoarium, x9. (See also plate X, and remarks on p. 158.) 



Figs. 6 to 10. Ehinidictta bxigua Ulr 131 



6 and 7. The basal part of a specimen of the natural size and xg. One of the branches has 

 three, the rest of the zoar;um four rows of zooecia. 



8. A delicate fragment with only three rows of zooecia, 



9 and 10. A branching fragment of the natural size and the lower half X9, This has from 

 five to seven rows of apertures. 

 Lower third of the Trenton shales at Minneapolis. 



Figs. 11 to 17. Pachtdictya acuta (Hall) and varieties 15£ 



Figs. 11 and 12. A specimen of the natural size and a portion xg. Trenton limestone, 



Trenton Falls, N. Y. 

 13. A very small specimen, with only six and seven rows of zocecia, from the Galena lime- 

 stone near Fountain, Minn. 

 14 to 16. Three specimens from the Galena shales near Cannon Falls, Minn. 



17. Surface, xg, of a well preserved fragment from the same horizon and locality as the pre- 



ceding. (See also plate IX.) 

 Figs. 18 and 19. Pachydictya elbgans, n. sp 15i 



18. A very nearly perfect zoarium of this species, natural' size, from the lower part of the . 



Galena shales at St. Paul. Later collections show that this species Is ^ceedingly 

 abundant at that locality and that the specimen here figured divides with greater 

 frequency than usual . 



19. Enlargement of the beautifully ornamented surface of same, xi8. (See also plate IX.) 

 Figs. 20 to 27. Pachydictya occidbntalis Ulr 151 



20 to 24. Five specimens of the natural size, illustrating the variable character of the zoaria. 

 25. Surface of flg. 24, xg. 



26 and 27. A frond of the natural size and a portion of its surface xg, traversed by irregular 

 grooves caused by interruptions in the development of the zocecia. (See also plate IX.) 

 Upper third of the Trenton shales at St. Paul. 



Figs. 28 to 34. Pachydictya fimbkiata Ulr 152 



28 to 30. Three specimens of the natural size, the last one the widest seen. 

 31 and 32. A very narrow and seemingly young example, natural size and the upper part xg. 

 33 and 34. An excellently preserved fragment of the natural size and a portion xg. This pre- 

 sents the fully matured condition of the species. (See also plate IX.) 

 Middle third of the Trenton shales at Minneapolis and St. Paul. 



