430 NOTICES OF THE MEETINGS [April 28, 
cation of the working of a general law of another kind, and one, 
which seems to me to depend on the manifestation of the relation of 
Polarity. 
We are accustomed to group all geological epochs under three 
great sections, the Paleozoic, or oldest, the Mesozoic or middle, and 
Cainozoic, more commonly termed Tertiary, or newest. If we con- 
sider the faunas (and floras) of these three great sections, we cannot 
but perceive that there is a far stronger affinity between the Mesozoic 
and Tertiary epochs than between the Mesozoic and Paleozoic. 
This is especially manifest when we regard the details of the distri- 
bution of those preservable forms of animal life, which being inhabit- 
ants of the medium in which sedimentary strata are deposited, are 
most likely to afford an approach towards complete evidence. On 
the other hand, the forms of life that characterize the Paleozoic 
formations, the products of a vast succession of time-periods, have, 
when regarded in their totality, a wonderful agreement and relation- 
ship among themselves. 
For this reason I propose to denominate the sum of the epochs 
after the Parmozoic, by the name of Nxozoic. 
Now if we regard these two great periods separately, we find that 
the manifestation of generic types during each exhibits striking and 
contrasting phenomena. The maximum development of generic types 
during the Paleozoic period was during its earlier epochs ; that during 
the Neozoic period towards its later epochs. And thus, during the 
Paleozoic period, the sum of generic types and concentration of 
characteristic forms is to be observed in Silurian and Devonian 
formations; during the Neozoic period it is during the Cretaceous, 
Tertiary, and present (itself part of the Tertiary) epochs that we find 
the maximum development of peculiar generic types (or ideas). On 
the other hand, during the closing epochs of the Paleozoic and the 
commencing epoch of the Neozoic period there was a poverty in the 
production of generic ideas, with few exceptions the species of the 
epochs in question being members of genera that form constituents 
in the assemblage, accumulated during the epochs of maximum of 
generic types or ideas. 
The following table may render my meaning more evident : 
Present and Tertiary “caren te of maximum development 
Neozoic ) Cretaceous epochs of \Neozole (Genedie typed? 
period Oolitic epochs . . .  . Intermediate. 
Triassic epochs Epochs of poverty of production 
Permian epochs of Generic types in Time. 
Paleozoic | Carboniferous epochs % . Intermediate. 
period Devonian epochs Epoch of maximum development 
Silurian epo chs of Paleozoic Generic types. 
Before the Silurian and after the commencement of the present, 
no special creations of generic types have as yet been shewn to be 
manifested, In the system of life of which all known creatures 
