1865.] BRITISH ASSOCIATION. 453 



tiuct Fauna and Flora, and a corresponding series of physical 

 conditions. These are the Lower Silurian, the Upper Silurian, 

 the Devonian and the Carboniferous, each of which constitutes a 

 great cycle of Palaeozoic time. The rocks supposed to be Cam- 

 brian are imperfectly known, and have afforded no fossils. The 

 Permian group has not been recognized. 1. The Carboniferous 

 Flora maybe arranged in three subordinate groups: (1.) That 

 of the Upper Coal Formation, consisting of a few of the more 

 widely-distributed species of the preceding Middle Coal Formation. 

 (2.) That of the Middle Coal Formation, the head-quarters of the 

 peculiar Carboniferous Flora, and of the productive beds of coal. 

 (3.) That of the Lower Carboniferous Coal Measures, consisting 

 of a few peculiar species, several of which are not found in the 

 overlying parts of the system. These plants have been widely 

 recognized at this period in Eastern America, and a similar group 

 seems to have existed at the same time in Great Britain. The 

 whole Coal Flora in British North America may be estimated at 

 about 150 good species, of which the greater number are common to 

 America and Europe. — 2. The Devonian rocks in Eastern America 

 have afforded eighty-one species of land plants, of which only about 

 ten are common to this and the Carboniferous period. They occur 

 principally in the Upper Devonian, but some extend to the bottom 

 of the system. Though fewer in species, the Devonian Flora is 

 not lower in grade than that of the Carboniferous period. The 

 earliest known species were allied to Lycopodiacese. *The De- 

 vonian Flora has been recognized in Pennsylvania, New York 

 Ohio, Canada, Maine,- and New Brunswick. The number of 

 species common to the Devonian of Europe and America is not so 

 great as in the case of the Carboniferous. 3. The Upper Silurian 

 has afforded land plants only in its upper beds, and only at Gaspd, 

 in Lower Canada. The only well-characterized species is Psilo- 

 phytonprinceps, which is also one of the most common plants in the 

 Devonian. The first known appearance of land plants in America 

 is thus at the same geological period with their first known appear- 

 ance in Europe. 4. The Lower Silurian has as yet afforded no 

 land plants. It abounds in objects called fucoids, but the greater 

 part of them are trails of worms, crustaceans, and mollusks, rill- 

 marks, shrinkage-cracks, &c. Those that show carbonaceous 

 matter or structure seem to be allied to modern Algae. The 

 extent of shallow-water deposits of the Lower Silurian explored in 

 Eastern America without any discovery of land plants, would seem 

 Vol. ii. ee No. 6. 



