OCCURRING IN THE VARIOUS STRATA. 11 



equal thickness, not unlike the concentric rings of a recent coniferous or 

 dicotyledonous tree, a person might be induced to believe that a portion 

 of these carbonaceous deposits may have indeed been composed of plants 

 belonging to the phanerogamic class. 



In the deposits included in the second period of Brongniart, which 

 extends from the magnesian limestone, to the keuper sandstone, and thus 

 includes the red or Exeter conglomerate, the magnesian limestone or zech- 

 steiu, the new red sandstone or gres bigarre, the muschelkalk or calcaire con- 

 chylien, and the red or variegated marl or keuper, no great variety of fossil 

 vegetable remains have been yet discovered. Those which have occurred, 

 appear to be principally composed of agamic and vascular cryptogam ic 

 plants, such as Fuci, Equisetaceae, Lycopodiacese, Filices, &c. 



In the oolitic fields, or the third period of Brongniart, the vegeta- 

 tion appears to have assumed a more peculiar character. The occurrence 

 in these deposits of so many fragments retaining externally the characters 

 of dicotyledonous woods, naturally induced those who have so long and so 

 assiduously laboured in these repositories, at once to assign to them the pe- 

 culiar character of possessing those plants. Cycadeas, Ferns, Equisetaceae, 

 and Coniferae, almost entirely compose the flora of this period. 



Among the numerous stems found in the various strata on the eastern 

 coast of Yorkshire, and in other parts of England, which I have had the 

 opportunity of examining, I have hitherto met with none presenting the 

 texture of a true dicotyledonous tree. All that have yet been examined, 

 appear to have belonged to the gymnospermous phanerogamic class. When, 

 however, as much time and trouble have been bestowed upon the fossil 

 vegetables of this period, as upon those lower in the series, plants not sup- 

 posed to have been brought into existence till after the period of the chalk 

 deposits, may perhaps be unexpectedly brought into view. 



In these lias and oolitic deposits, we observe, as above stated, vascular 

 cryptogamic and gymnospermous phanerogamic plants deposited together. 

 Now, the more recent vegetable deposits, such as that of Bovey, and the 

 extensive beds on the Rhine, so ably described by Dr Hibbert, are evident- 

 ly composed chiefly of plants possessing woody texture arranged in con- 



