PLATE XXXIX. 



Fbnestella (Polypoka) robusta. 



Page 156. 

 See Plates 34, 37 and 4«. 

 Pig. 1. A specimen, natural size, showing angular branches and dissepiments. 



Fig. 2. An enlargement of a portion of the non-celluliferous face of a macerated frond, showing the 

 texture of the solid portion of the branches. The lower portion of one of the branches is stiU 

 further worn away, showing the bases of the polygonal cells. 

 Fig. 3. An enlargement of a portion of fig. 1, showing more distinctly the character of the branches and 

 dissepiments, when in their natural condition. 



Upper Helderberg group. Walpole, Ontario, Canada. 



Fenestella (Polypoka) nexa. 



Page 166. 



Kg. 4. A portion of the non-cellulifei-ous face of a fi-ond, showing the size of branches and dissepi- 

 ments, and their manner of gi-owth. 



Fig. 5. A portion of the celluliferoiis face ' •" ~ T ;' ' ize. 



Fig. 6. A portion of the, non-celliUiXei-ouis ~irg«(l,,«howii>g^Qgul»r, l^ranches, narrow 



dissepiment.s, and strong striatioiib on two of tlie bi-anches. . (X 0.) 



Fig. 7. An enlargement of a i>ortion of fig. 4. The branches are rojriilarly rounded, and dightly nar- 

 rower than the fenesti-ules. (X 6.) ' "1 / M -j: I 



Fig. 8. All enlargement of the ujiixT portion of fig. 4. Thn branrUi's are very irregufari H)Unaedi* Vf 

 carinated, and fre(iitently less than one-half 'the width of the fbnestriiles. (X 6.) '' ■^'' 



Fig. 9. An enlargement of a portion of fig. .5, showing moi-e distinctly the form and coni'imrative size of 

 the ))ranch<'s and dissepiments', the form and arrangements of the' cell apertures and the lon- 

 gitudinal RtriiE on a portion of one branch. (X 8.) 



Upper Helderberg group. 'WaXpole, Ontario, CiinaSa. 



FEXK.'^TEt'L.i (1^<^^^0«^)" ste'l^AUATA'. " ' 



Fig. 10. The celluliferoiis side of a .specimen, natural size, showing th« si^e of ^he branchea and dissepi- 

 ments, and their maouer. of jjrowUi. II Ml , J - 1 .,1 r,l,|'.|| r . , ', 



Fig. 11. An enlargement of a portion of fig. in, showing moi-e distinctly the character of the branches and 

 dissepiment!*, their comparative size ; the form and arrangement of cell apertures, and the 

 longitudinal stria' stjparating the ranges of apertures. (X 6.) 

 Upper Helderberg group. Walpole, Ontario, Cantida. 



Fenestella (Polypoka) mutabilis. 



Page 106. 



Fig. 12. A portion of the non-celluliferous fa<;e of a frond, natural size. 



Fig. 13. A portion of fig. 12 enlarged. The branches are strong, wider than the fenestrules, rounded, 

 with a narrow carina along the middle. The upper jiortion of the branches is strongly striated, 

 the dissepiments carinated. (X 6.) 



Fig. 14. An enlargement of another jiortion of fig. 12 ; the branches are more irregular than those of 

 fig. 13 ; not so strong and more angular ; the dissejiinients are angular. (X 6.) 



Fig. 15. An enlargement of a portion of the celluliferous face of a frond, .showing the form and compara- 

 tive size of the branches and dissepiments, and the form and ari-angement of the cell aper- 

 tures. (X 6.) 



Upper Helderberg group. Walpole, Ontario, Canada. 



