281 
On page 981 the author quoted, in speaking of the Old Red Sandstone, 
says: 
x * * in innumerable sections where the lowest strata of the sys- 
jem are found graduating downward into the top of the Ludlow group; 
and where its highest beds are seen to pass up into the base of the Car- 
boniferous system. 
On page 982 one reads as follows: 
The rocks termed Lower Devonian may partly represent some of the 
later phases of Silurian life. On the other hand, the upper parts of the 
Devonian system might in several respects be claimed as fairly belonging 
to the Carboniferous system above. 
As to the relation of the Lewer Carboniferous to the Devonian, Geikie 
(Text-book, p. 1014) says: 
Both in Hurope and America it may be seen passing down conform- 
ably into the Devonian and the Old Red Sandstone. So insensible indeed 
is the gradation in many consecutive sections where the two systems join 
sach other that no sharp line can be drawn between them. The strati- 
graphical passage is likewise frequently associated with a corresponding 
commingling of organic remains. 
Chamberlin and Salisbury (Geology, ii, p. 499) tell us that the transi- 
tion from the Devonian to the Mississippian seems to have been accom- 
plished without netable deformative movement. Also (p. 518) it is stated 
that the Devonian fauna passed by graduation into the Mississippian. 
There exists in many places the same doubt regarding the boundary 
line between the Carboniferous and the Permian. Geikie (Text-book, p. 
1064) states that in the Midlands and the west of England no satisfactory 
line can be drawn between the two systems; (p. 1065) that the flora of 
the older Permian rocks presents many points of resemblance to that of 
the Carboniferous; (p. 1063) that in North America no good line of sub- 
division exists between Permian and Carboniferous; so certain deposits 
are called Permo-Carboniferous; (p. 1077) that in Russia the Permian 
attains an enormous development, the horizontal strata nearly lying con- 
formably on the Carboniferous. 
Of the Permian of North America Chamberlin and Salisbury write 
(Geology, ii, p. 620): 
The upper Barren Measures are commonly separated from the Penn- 
Sylvanian on the basis of the plant species rather than because of any 
stratigraphic break at their base. 
