318 J. D. Dana on American Geological History. 
Before continuing the review, I will mention some conclusions 
which are here suggested. 
I. In the first m8 through the periods of the Silurian and 
Devonian, at twelve distinct epochs at least, the seas over this 
times occurre 
If Omnipo otent Power had pet. sane’ to making monads for 
ier 
required again and again the sowing of monads, a. there would 
failure of crops after all; for these extermina- 
tions gene to occur through all geological time into the Mam- 
malian 
U. enn, I have observed that the continent of North 
America has never been the deep ocean’s bed, but a region of 
4 Seta and Epochs thus made out are as follows—excluding minor subdivisions 
ub-epochs, and not a to give the parallel subdivisions 
for th the West. On this subject, the volumes and papers by Prof, Hall especially 
should be consulted. 
ge (Sta AGE. 
1. Lower Siluria 
1. Porspam cates wy Potsdam —— 2nd. Calciferous sandrock. 
poch. Chazy limestone; 2nd. Birdseye; 8d. Black 
. Hupson Pzriop.—Ist Epoch. Utica Shale; 2nd. Comet River Shale. ~. 
son River Shale and Blue limestone of Ohio in parts of the west.) 
2. Upper Silurian. 
1, Nracara Penton, vir Epoch, Oneida Conglomerate; 2nd. Medina Sandstone ; 
« Clinton a ; 4th. Niagara Grou 
2. Ononpaca Pzrtov.—Ist Epoch. Galt me 2nd. Onondaga Salt Group. 
3. Lowzr ata DERBERG Penrop.—Limestones. (Statement of epochs here omitted). 
Il. DEVON — AGE. 
1, Ontskany Pertop.—Ist Epoch. Oris andstone ; Cauda-galli Grit. 
ee Urrer Hetpseserc Prriop.—lst Epece, Sictene bate ‘ond. Upper Helder- 
Tg group. 
3. Hawiuron Pertop.—1st Epoch. Marcellus Shales; 2nd. Hamilton group; 3d. 
Gunnar Slate. 
4. rome Psriop.—1st Epoch. P eras Chem 0 
i Partop.—Catskill Red San es and Shales, (No. LX. of Rogers) 
83 & ‘jekneee =: 
1, SuBCARBONIFEROUS dene Epoch, eee es and Shales 
(with some coal — d. Sandstones, Shales and Cacbeatwons limestone. 
Nos. X. and XI. of Rogers 
2. Carponirerous Prriop.—lst sage @ — Grit ; 2nd. Lower Coal Meas- 
wane 83d. Upper Coal Measures. L and XIIL. of R ogers. 
3. PrwtaN Pens ERIOD.— Probably Be resented in Eastern North America, except 
by the events of the Appalachian eval eo 
