GENERAL LAWS OF ORIGIN AND MIGRATION. 265 



Bearing in mind these peculiarities of the area in 

 question, we may now group in a tabular form the dis- 

 tinct specific types recognised in the Eriau system, indi- 

 cating, at the same time, those which are represented by 

 identical species in the Carboniferous, those represented 

 by similar species of the same general type, and those not 

 represented at all. For example, Calamites cannmformis 

 extends as a species into the Carboniferous ; Asterophyl- 

 lites latifolia does not so extend, but is represented by 

 closely allied species of the same type ; Nematophyton 

 disappears altogether before we reach the Carboniferous. 



