New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1879-08-23
LIFE OF THE SILURIAN AGE.
BY S. W.. FORD.
g1IE LOWER HFLDFRBTRG AND oRIsKANT fEl"oD'
or Tue Upper suVRIAN.

TIIE LOWER HFLDERBTRG AND oRIsKANY fEiuoD'
OF THE UPPER sILuRIAN.
Tho period that followed the Sauna Vhe No"
HelderheTgl was one of extensive limestone nan
inc, and TO this succeeded period OF SANDSTONE
woking the Oriskany). The Lower Helderoerg
reriod derives its name from the o'rcums'apco ,a'
the rocks representing 1t are typicliiy ulSpl"l'u "
a. Io,,ar nortion of the Heidelberg Mountains IN
The STATE of New-York. The formation mas
tbere q thickness of 400 feet ana con-
sists Of several subdivisions usually not
recognizable IN other regions, of which the primer
nal one is the Water-lime group. This group is also
ths Lowest and. a. viii be further on Is char
acterzel bv the presence of certain organic remains
of exceptional interest. The Lower Heidelberg Is
eminenilv an Appalachian formation, stretching
southward from New-York into TenneSseesand th'h-
ming out To the West. The Water-lime has oeeh
recognized by Dr. Newberry in Ohio where he s'a''S
"it forms feather edge on the TANKS OF the O'ci"
natl arch" bis arch having been formed at ne sum-
time with the elevation of the Green Nouh'd'"
region Of which mention was made IN my i'S' al
49,, o,d be adds This shows that the sea IN
which the Water-lime was deposited ieacneu "uv
mart way M the slope Of the old silurian island"
Tho Or,slonv sandstone, ON the contrary, thickens
westward. and presents feather edge toward the
II,dson II extends westward from New-Iork into
Indiana and Missouri and sOuthward along the APP
pslacbians 1t is often almost wholly made mp OF
large fossil shells of which more particular note
will be made bye and bye.
The approximate equivalents OF the Lower
Heidelberg and Oriskany beds in foreign countries
are. in Great Britain following the ascending order
~ the Ludlow rocks including the Lower Lud-
low, ne Aymestry limestone and the upper Luz
low; and " the HlestOnes; IN BOHEMIA Dur
rapdc's Stages TO II inclusive; and IN sweden
,ortio, of Aucelin's Region f. The Tilestones OF
Great Britain and the Oriskany sandstone OF North
America arc regarded as beds Of passage between the
S,lprian and Dcyonian systems As IN the last
article so in this the life Of the two periods under
consideration will be taken up separately, begin
ming with the Oldest
LOWER HELDERBERG PERIOD.
The beds of the Lower Heidelberg vie with those
of the Trenton and Niagara in the protuson ana
beautv of their organic remains. Very little Is
known concerning the plant life of the period, but
thus far no evidences of terrestrial vegetation
have been obtained. The highest forms OF animal
life vet brought to light from the American Deds
are Crustacean but 10 the Ludlow rocks OIL Ureat
Britain. and their equivalents in Russia ana
Bohelpa q considerable number Of species Of fishes
have been found, these being the Oldest known
Vertebratos. or animals provided with a backbone.
There was. thus, a great step forward made In the
EXPRESSION of the different types OF animal struc-
fnre. Moreover, al or about the same time with
the first appearance of the fishes, new tribe OF
Crusta,cans come upon the scene, standing out IN
tbelr structural characters clear and distinct
from all the earlier forms. These facts alone
serve 10 render the period of peculiar interest
and when the Invertebrate ife or that represented
nv the Crustaceans Mollusks, Radiates. ETC., as
whole comes TO be treated Of shall find range
Of facts tending to Chamberlain manner scarcely
less conspicuous, the Lower Heidelberg as one OF
the most strongly marked periods Of Silur1an time
The Fishes of the Ludlow rocks and their Bohe-
,pian eouiyaIents include both Ganoids and Sc
lacans OF those types of ichthyic structure exem-
rl6ed IN our own time by the Gar-plke and Shark
respectively. Among Ganoids there are two great
groups. one distinguished by having the body en-
cased in an armor of polished bony scales frequently
of n rhombic shape, and overlapping each other
like the tiles Of roof. as in the
Gar; and the other by having the body
protected either wholly or in part by bony plates,
often richly ornamented and generally OF larger
size in the region of the vital organs The name
"Placoderms" has been applied to the fishes of the
latter group in alluson to their large dernal body
pilates; and some notion TO how the
old-time forms were built may be formed
by the study of another modern day
Ganold. and contemporary Of the Gar-pike
the Sturgeon. A few other types of the order, ex-
}sting in our present waters, do not appear TO fall
into either of these groups, but these need
not here be dwelt upon. The term Ganoid
Figs.I.3,