GQ 



ME. D. DATIES OX THE ECOLOGY OF [vol. IxXA'ii, 



If we adopt a balance of the three opinions quoted above, it 

 would seem that the probable conditions of the land-surface pre- 

 vailing during the sedimentation of the shales of the ten horizons 

 dealt with in this paper might be expressed in the following table. 



Name of seam. 



Percentage compositii^n 

 of flora. 



Probable physical 

 conditions. 



Five-Foot Seam. 



Middle Yiird Seam 



Upper Yard Seam. 



NiBe-Foot Seam 



Six-Foot Seam 



Equisetales 30-34 p. c. 



L.ycopodiales ... 0-21 p. c. 

 Filicales and 



Pteridosperms 24-46 p. c. 

 Cordaitales 43-84 p. c. 



Equisetales 72'96 p. c. 



Splienopliyllales 0-18 p. c. 

 Lycopodiales ... 0-49 p. c. 

 Filicales and 



Pteridosperms 24-41 p. c. 

 Cordaitales I'So p. c. 



Equisetales 



Lycopodiales ... 

 Filicales and 



29-04 p. 

 9-82 p. 



c. 



c. 



Pteridosperms 

 Cordaitales 



37-68 p. 

 6-24 p. 



c. 

 c. 



Two-Foot Nine Seam . 



Eqiiisetales 49-74 p. c. 



Lj'copodiales ... 3-33 p. c. 

 Filicales and 



Pteridosperms 27-55 p, c. 

 Cordaitales 17-03 p. c. 



Equisetales 39-94 p. c. 



Lj'copodiales ... 0-44 p. c. 

 Filicales and 



Pteridosperms 43-77 p. c. 

 Cordaitales 14-15 p. c. 



A large extent of dry land, 

 and possibly upland. 



The fact that Lycopodiales 

 are weak suggests a restric- 

 ted area of swamps. 



The conditions must have 

 been very similar to the 

 period of the formation of 

 the Five-Foot Seam. It 

 will be noticed that the 

 Jjycopods are rare, and that 

 dr^'-land vegetation is much 

 in evidence. 



There has been a slight 

 change in the land-surface. 

 Dr^'-land flora increases, 

 probabl}' owing to the up- 

 lift of the land surface. 

 The fact that the Lj'copods 

 are more abundant sug- 

 gests more swampy areas 

 in places. 



Dry-land plants are rarer in 

 this seam than in the 

 Upper Yard Seam, and the 

 Lycopods are also fewer 

 in number. We may infer 

 that the land-surface was 

 depressed and of no high 

 altitude, yet with swampy 

 areas less prevalent. 



Thifi period includes possibly 

 the highest elevation of 

 the land - surface. The 

 ferns and fernlike plants 

 are dominating the other 

 classes of plants. Swampj' 

 areas are limited, hence the 

 rarity of Lj'copods. 



Equisetales 5-96 p. c. :Tlie inference here is, that 



Lycopodiales ... 66-38 p. c. 

 Filicales and 



Pteridosperms 1-70 p. c. 

 Cordaitales 25-13 p. c. 



there was an extensive low 

 land-surface covered with 

 huge marshes. The up- 

 lands were limited to small 

 areas, upon which the few 

 Filicales and Pteridosperms 

 flourished. The chances of 

 the preservation of the 

 latter plants were only one 

 in forty, as the evidence 

 shows. 



