462 Notices of Memoirs—Prof. Boyd Dawkins’s Address. 
of Eocene age, and what has been recognized in them as a newer 
or Miocene facies is due to their having been first studied in Europe 
in latitudes which only became fitted for them in Miocene times. 
When stratigraphical evidence is absent or inconclusive, this un- 
expected 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 Pole region is the centre of 
dispersal, from which the Dicotyledons spread over the Northern 
Hemisphere. If it be true—and I, for one, am prepared to accept it-—— 
it will follow 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-Chapelle. 
I would remark further, before we leave the floras behind us, that 
the migration of new forms of plants into Kurope 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 Carboniferous period, after 
the great change in geography at the close of the Neocomian. ‘The 
Secondary Plants preceded the Secondary Vertebrates by the 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, in one of his many sdaeaaees which have left 
their mark upon our science, has called attention to the persistence 
of types revealed by the study of Paleontology, 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 
in the Invertebrata amounts only to 6 out of 88, or about seven per 
cent., while in the Vertebrates it is not less than 12 out of 40, or 30 
per cent. These figures imply that the amount of ordinal change in 
the fossil Vertebrates stands to that in the Invertebrata in the ratio 
of 30 to 7. This disproportion becomes still more marked when we 
take into account that the former has less time for variation than the 
latter, which had the start by the Cambrian and Ordovician periods. 
It follows also that as a whole they have changed faster. 
