SS é Hy ky 
308 J. D. Dana on American Geological History. 
and crinoids, the lower fixed or ae — with rare ex 
ceptions, occur in the Silurian or Molluscan Age , 
e Articulata ha Radiata thus Bepin early, but with only r 
the faves forms in each, and neither is a ia class in any — 
Vie nied the history, then, zodlogically, the ages are—the Age 
, of Mollusks, of Fishes, of Reptiles, of Mammals, of Man. 
& We ai satite change the point of view to the Vegetable King- 
dom. The ages thence indicated would be three:— 
I. The Age of Alger, or marine planis, obieeepitaiae to the 
Silurian and Devonia 2 
Il. The Age of opi or flowerless trees, that i ~y the Tie : 
dodendra, Sigillarie, and Calamites,—corresponding to the Coal 
which may still be retained, as i r from certain that the 
Sigillarizs and Calamites are most Beaty related to the Conifere, = 
The Age of Angiosperms, or our common trees, like ae 
Oak, Elm, &c., beginning with the Tertiary. 2 
The terval between the second and third of these apes i8 is | 
ssehepieks conte by Conifer, the Pine tribe, and Cycadew, the - - 
true Gymnosperm’, species of which were abundant in the ‘Coal 
Period, and have continued common ever since. The : 
in the iaslecey. of dais flowers and their naked seeds, are next 
akin to the Acrogens or flowerles trees. Although in the main: 
a flowerless vegetation, for the few supposed remains of flowers 
observed abroad have been recently referred to ee a 
leaf-buds, it appears probable from the observations of Dr. % 
berry, that there were some true flowers over the Ohio prairie 
ciety monocotyledonous, and related to the Lily tribe. 
of P. or monocotyledonous trees have -— 
in tha coal fields of this country. 
Period and Permian, between the Age of Fishes and me: of 
Reptiles,—a space in time zovlogically occupied by the apna + 
ping of these two ages 
* This Age, would perhaps be more correctly styled, the A Coni, 
Conifers, a higher group than Acrogens, were Sty ear! si of uf all land pla 
the upper pt ae ell as Carbonifero ages in ¢ 
be ref eos pe 
Calantes ton yee related to the Conifers 
s in some cases ar to tare approached ae ; reptiles 
rome 0 Fhe genera of Aacptie the Conifers. An interesting sao of 
be e coal formation of Ohio, has recently been mentioned by Dr. J. Wyman, 
eeting Amer, Assoc. at Abate) 
