281 



On page 9S1 the author quoted, in speaking of the Old Red Sandstone, 

 says : 



* * * in innumerable sections where the lowest strata of the sys- 

 tem 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 Lower Carboniferous to the Devonian, Geikie 

 (Text-book, p. 1014) says: 



Both in Europe 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 

 each 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 notable deformative movement. Also (p. 51S) 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 Permiau 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 

 sfratigraphic break at their base. 



