218 Prof. J. Van der Hoeven on the Succession and 



the Carboniferous period. The remaining species of this flora 

 are referred to the Lycopodiacese and Equisetacese*. The second 

 period includes all the strata above the Coal -formation to the 

 Upper Red Sandstone. In comparison to the first, the number 

 of vegetable remains is only small; but, besides Acrogens, we 

 observe amongst them Coniferous trees and Monocotyledons. 

 In the third period, which comprehends the Oolitic and Creta- 

 ceous group, Cycadeacese are predominant, and next to them 

 follow iferns, the rest consisting chiefly of Monocotyledons. 

 The fourth period embraces the Tertiary strata. It is only in 

 this that remains of Dicotyledons are numerous. 



These results have been in part modified by new discoveries ; 

 but even now it is certain that there is a great diversity between 

 the species and genera, and even the greater divisions of a former 

 and later vegetable and animal world. As to these modifications 

 in the results of palseontological inquiry, it is now proved that 

 the opinion of Cuvier, by whom the first apparition of land- 

 mammals was stated to have been posterior to the Chalk period, 

 must be given up. Already, during the lifetime of Cuvier, 

 some few remains (lower jaws) of mammals were found in the 

 slate of Stonesfield, which was proved to belong to the lower 

 Oolitic strata, and consequently to be of a much more ancient 

 date than the Chalk formation, on which the Tertiary strata are 

 resting. In the last decennium, several new examples of mam- 

 malian bones found in oolitic strata have been brought to light f; 

 and low in the Upper Lias two molar teeth have been found, in 

 1847, which Plieninger refers to a mammalian genus called by 

 him Microlestes. 



But it seems that it would be overrating the value of these 

 facts if we inferred from them that all great classes of the animal 

 kingdom existed from the first beginning of life on the surface 

 of the globe, that all were represented by difi"erent species, from 

 the first geological periods till the modern era. In comparing 

 the florae and faunae of diff'erent countries — a comparison which 

 forms the fundamental part of a geography of plants and ani- 

 mals — we must look chiefly to the dominating groups, to the 

 families and genera which are distinguished by the larger num- 

 ber of species. In the same manner, the characteristic features 

 of different geological periods in relation to organic beings 



* To these must be added some Coniferous trees, more allied to Arau- 

 cariae than to any of our European firs. 



t In the freshwater strata of Purbeck there were discovered, in 1856 

 and the following years, a number of lower jaws, and even a fragment of 

 a skull, of mammals, forming diflFerent genera, and partly aUied to the in- 

 sectivorous marsupial genus Amphitherium of Stonesfield. (See Sir Charles 

 Lyell, Supplement to the fifth edition of a Manual of Elementary Geology, 

 Lond. 1857, 8vo, pp. 16-27.) 



