646 EEPOKT— 1888. 



Nor do we find evidence of greater variation in the dicotyledonous forests, from 

 their first appearance in the Cenomanian stag-e of the Cretaceous rocks of Europe and 

 America, through the whole of the Tertiary Period down to the present time. In 

 North America the flora of the Dakota series so closely resembles the Meiocene of 

 Switzerland that Dr. Heer had no hesitation in assigning it in the first instance to 

 the Meiocene Age. It consists of more than one hundred species, of which about 

 one-half are closely allied to those now living in the forests of North America — 

 .sassafras, tulip, plane, willow, oak, poplar, maple, beech, together with Sequoia, the 

 ancestor of the giant redwood of California. The first Palms also appear in both 

 continents at this place in the Geological record. 



In the Tertiary Period there is an unbroken sequence in the floras, as Mr. Starkie 

 Gardner has proved, when they are traced over many latitudes, and most of the 

 types still survive at the present day, but slightly altered. If, however, Tertiary 

 floras of difierent ages are met with in one area, considerable differences are to be 

 .seen, due to progressive alterations in the climate and altered distribution of the 

 land. As the temperature of the Northern Hemisphere became lowered the tropical 

 forests were pushed nearer and nearer to the equator, and were replaced by plants of 

 colder habit from the northern regions, until ultimately, in the Pleistocene Age, the 

 Arctic plants were pushed far to the south of their present habitat. In consequence 

 of this Mr. Gardner concludes that ' it is useless to seek in the Arctic regions for 

 Eocene floras as we know them in our latitudes, for during the Tertiary Period the 

 climatic conditions of the earth did not permit their growth there. Arctic fossil 

 floras of temperate and therefore 1\1 eiocene aspect are in all probability of Eocene 

 age, and what has been recognised in them as a newer or Meiocene facies is 

 due to their having been first studied in Euroi)e in latitudes which only became 

 fitted for them in Meiocene times. "When stratigraphical evidence is absent or 

 inconclusive, this unexpected persistence of plant types or species throughout the 

 Tertiaries should be remembered, and the degrees of latitude in which they are 

 found should be well considered before conclusions are published respecting their 

 relative age.' 



This view is consistent with that held by the leaders in botany, Hooker, Dyer, 

 Saporta, Dawson, and Asa Gray — whose recent loss we so deeply deplore — that the 

 North Polar region is the centre of dispersal, from which the deciduous Dicotyledons 

 spread over the Northern Hemisphere. If it be true — and I, for one, am prepared 

 to accept it — it will i'ollow that for the co-ordination of the subdivisions of the 

 Tertiary strata in various parts of the world the plants are uncertain guides, as they 

 have been shown to be in the case of the Primary and Secondary rocks. In all 

 cases where there is a clash of evidence, such as in the Laramie lignites, in which 

 a Tertiary flora is associated with a Cretaceous fauna, the verdict in my opinion 

 must go to the fauna. They are probably of the same geological age as the deposit 

 at Aix-la-Ohapelle. 



I would remark further, before we leave the floras behind us, that the migration 

 of new forms of plants into Europe and America took place before the arrival of the 

 higher types in the fauna, after the break-up of the land at the close of the Car- 

 boniferous period, and after the great change in geography at the close of the 

 Neocomian. The Secondary plants preceded the Secondary vertebrates by tlie 

 length of time necessary for the deposit of the Permian rocks, and the Tertiary 

 plants preceded the Tertiary vertebrates by the whole period of the Upper 

 Cretaceous. 



Let us now turn to the fauna. 



Professor Huxley, 'n one of his many addresses which have left their mark upon 

 our science, has called attention to the persistence of types revealed by the study 

 of Palaeontology, or, to put it in other words, to the singularly little change which 

 the ordinal groups of life have undergone since the appearance of life on the earth. 

 The species, genera, and families present an almost endless series of changes, but 

 the existing orders are for the most part sufficiently wide, and include the vast 

 series of fossils without the necessity of framing new divisions for their reception. 

 The number of these extinct orders is not equally distributed through the animal 

 kingdom. Taking the total number of orders at 108, the number of extinct orders 



