69 
limestone, which covers the oldest 
in some places, or elsewhere is un- 
der the sandstone or slates. The 
same happens in the long but narrow 
formation of limestone called transi- 
tion, which borders on the mts. Al- 
leghany to the East dividing them 
from the primitive hills. The Tri- 
lobites and Terebratulites, &c. are 
there also silicified. While in the 
limestones of New-York N. of the 
Alleghany, or superposed to the E. 
of them, the fossils are nearly all 
calcareous. And in the vast marl 
region from Long Island to Florida 
along v the sea, all the fossils are cal- 
careous or marly. A few later fos- 
sils of Kentucky, &c.. not silicified, 
are chiefly found in marly forma- 
tions. j 
The fossils of this central region 
can therefore be known at first sight 
when seen silicified in, limestone. 
Thus the cyclorytes and silicified 
alcyonites may well be animals like- 
wise. This becomes very clear when 
many of them are seen, which ap- 
proximate to living animals of the 
Tropical seas and Mediterranean. 
As a striking instance I add the 
descriptions (and figures -in the ori- 
ginal) of 2 N. G. of mine from the 
sea of Sicily. 
1. Psadiromarubra,Jl&L Analyse 
Nat. 1815. Family of Polactomes — 
Animal fixt upon shells, fleshy red, 
smooth, elliptic, flattened, margin 
irregular, many flexuose concentric 
strias, centre with an expansible 
mouth without tentacula. 
2. Peritrema lobularis , Raf* disc. 
1807. Family of Alcyons. — -Fixed on 
rocks, lobed, compressed, fleshy, 
brownish, with many rihgs on the 
surface, having ghole or pore in the 
centre. 
These two animals appear to re- 
present the ancient cyclorytes of the 
pelagic world,* but many more exist 
yet in the seas. 
_ It will therefore be needful to dis- 
tinguish with care among the silici- 
ous fossils with simple forms, those 
which are really inorganic, such as 
the orbicules, spirozoites, annulites, 
globulites, mamillites, lentilites,&€7 
and the organic fossils,* such as the 
fibril lit es, cyclorytes, bolactites, gra« 
nulites, &c. which may resemble 
them, and also the geodes from the 
geodites. If the silicious orbicules, 
&c, were always minerals, they 
should not be so rare, but common 
as the cristals inside of silicified 
shells. Out of thousands of silicious 
fossils which I have examined, I have 
only found cyclorites upon a small 
number. I have hardly ever seen 
any spiral epizoites and very seldom 
nodulose orbicules. But I have seen 
some radiated, and others with small 
circles within larger ones. The va- 
riety is great. If the free cyclorites 
were only orbicules they should not 
ibe So rare. Some are totally chang- 
jed in calcedony, they should then 
be deemed circular calcedonies,* but 
they are very different from the ma- 
niillar, and occulated calcedonies. 
Yet I was right to say that the fossil 
alcyonites^ form as it were, a link 
between animals and minerals, as 
they approximate in shapes,* but my 
fibrillites (decidedly organised ani- 
mals) proves the animality of many 
others gradually linked by the 
Forms. CkS.R. 
Philadelphia , 2 d Jpril, 1832. 
Note.— -The tendency to silification of 
all animal substances is so very great in 
the western strata, that even parts of 
bones and horns of quadrupeds have been 
found partly silicified outside. I have in 
my cabinet a remarkable instance of it in 
the fossil horn of my JVLazama salinaria , 
which is intact inside, but partly silicious 
outside : although this fragment was in a 
late formation, not in a stratum, and be- 
longs to the latest age of fossil animals. 
15. Remarks on the Geodes and Geodites. 
Every hollow mineral with cristals 
inside has often been called Geode. Pa- 
trin, ever since 1803 in the article Geode 
of the Diet,, of Nat. Mist, has very well 
distinguished the volcanic Geodes, front 
the Geodes of the chalk, which last he 
deemed fossil animals; 
Our ancient limestone agrees also with 
the chalk by having similar geodes; 
but there are two very different kinds 
of Geodes in our ancientlimestone. Some 
like those of the Niagara lime stone, 
