68 
America. This immense basin ex- 
tends from Canada to the Gulf of 
Mexico, and from the Alleghany to 
the Ozark mountains which are grit- 
ty mountains, while the basin itself 
is of very ancient limestone, altho’ 
quite horizontal, but often covered 
with hills of slate, coal and sand- 
stone. 
Prof. Brongniart has mentioned 
some of the fossils which I sent him 
in 1820 from this region, ( Terebra - 
tula , Shophomenes , Favosites) which 
had on them silicious orbicules. I 
could add many more as I have seen 
several others on Turbinolites , Or- 
thoceratites , &c. My Cy clo rites tur- 
binolia covers all over one of the 
first. I consider it like all my cy- 
clorites of the S. G. cyclepite as 
parasite animals become fossils along 
with their support. Among my G. 
Cyclorites published 1819, and a 
complete monography in 1831, 
there are some flat and fixed, oth- 
ers fixed branched, free and simple 
with 1, 2 or several orders of circles. 
While in my G.Fibrillites,the whole 
is striated in the interior as in 
the Tethya of Bonati and my G. 
Bolactites . 
Yet I do not doubt of the globu- 
' far and circular cristalization of the 
silex. Far from it, I have always 
believed in it for 30 years past, even 
when hardly any mineralogist could* 
believe if. Besides the mamillar 
and oculated calcedonies and agats, 
I have seen jasper, onyx, cornelian, 
quartz, and chert, &c. with cristals 
either mamillary or hemispherical or 
lenticular. I have several speci- 
mens in my cabinet, such as red 
jasper, blue and white onyx, &c. 1 
should therefore be inclined to be- 
lieve that some of the orbicules men- 
tioned or figured by Brongniart are 
orbicular cristals; but there are 
some, which with my cyclorites, fi- 
brillites and others omitted, have 
the appearance of being animal fos- 
sils ol ancient pelagic alcyonites, 
become silicious, like nearly all the 
fossils of the ancient limestone of \ 
Kentucky, Ohio, Tennessee, &c. 
It appears that the geologists do 
■ not yet know well this fine region 
) of fossils whose oryctology was first 
- explored by Clifford in 1 8 14 to 1820, 
[ and next by myself in 1818 to 1826. 
} Maclure has designated all the re- 
i gion west of the Alleghanies as-se- 
- condary, and James calls the same 
transition. Brongniart appears un- 
decided whether it is transition. In 
fact it is neither strictly the one nor 
the other! America is not always 
similar to Europe in all the forma- 
tions and strata. It has neither 
chalk nor lias? The Oolites and 
clays are often out of place! The 
ancient or pelagic limestone of this 
region as well as the slates and grits 
which surmount them are of transi- 
tion by their appearance and ancient 
tribes of fossils; but they are similar 
to the secondary of Europe, by the 
horizontal position of the strata, and 
the silicified fossils like those of the 
chalk. They form therefore a kind 
of peculiar series, deserving perhaps 
a peculiar name, since the English 
appellation of mountain limestone 
or carboniferous limestone do not 
properly apply; they do not form 
mountains, but inferior horizontal 
strata, and do but seldom bear the 
coal. I have called it compact when 
it is nearly homogeneous and specu- 
lar when it has a shining lamular 
fracture, &c. The fossils are dis- 
seminated in it very unequally, being 
sometimes very rare, but accumula- 
ted in some localities. Some species 
are very abundant and others very 
rare. Their great antiquity is proved 
by the ancient tribes to which they 
chiefly belong, Madrepores, Mille- 
peres, Turbinolites, Favosites, Te- 
rebratulites, Encrinites, Alcyonites, 
&c. with some Trilobites and Cepha- 
lopodes. 
But the most striking fact con- 
sists in the complete silicification of 
all these fossils of nearly 1000 dif- 
ferent species. Most of them are 
casts of destroyed animals replaced 
by a silicious matter. This is con- 
stant in the limestone, except in the 
newest and uppermost, the shaly 
