(genus Astacus). ā (b.) Insects. ā Species of Cnrculionites, Gla-
phyroptera, etc.
Fig. 660.
4. Vertebrates. ā (a.) Fishes. ā Among Hybodont Sela-
chians, fig. 469, Hijhodus j)licatilis Ag. ; fig. 468, H. minor
Ag. Among Cestracionts, species of Acrodns, Ceratodus,
etc. Ganoids especially of the genera Saurichthys, Gyro-
lejiis, Amhlypterus, and Palseoniscns, the last of the hetero-
cercal species; and of the Pycnodont division, Pycnodus
yif/as, etc.
(6.) Reptiles. ā (1.) Amphibians of the Labyrinthodont
tribe. Fig. 661, Labyrinthodon [Mastodonsanrus) (jiganteus,
reduced to one-twelfth the natural size. Fig. 661 a is one
of the large teeth, reduced one-half. They have the Laby-
rinthine structure explained on p. 280. Fig. 662 repre-
sents the prints of the fore and hind feet of a Chirotherium,
one-twelfth natural size, from a slab obtained at Hildburg-
hausen in Saxony, supposed to be those of a Labyrinthodon.
The larger track in one was eight inches long, the stride four-
teen inches ; in another, the length was twelve inches. Similar pemphix Sueurii.
tracks have been found at Storton Hill in England.
(2.) Lacertians and Saurians. ā The species of the Trias have biconcave ver-
tebrae, like the Thecodonts and Enaliosaurs (in this approximating to the Fishes).
A species of the Permian genus Thecodontosanrus is found in the Trias at Leam-
ington, England. The Rhynchosaur (R. articeps Owen) had the beak of a Turtle,
without teeth. Simosaur, Nothosaur, Pistosaiir, and Conchiosaur are names of
TRIASSIC PERIOD.
437
different genera of Swimming Saurians {Eiialiosanrs) of the Triassic, whoso
remains occur mostly in the Muschelkalk of Europe, and especially at Luueville,
Reptiles. ā Fig. 661, Skull of Labyrinthodon (Mastodonsaurus) giganteus (X ]\); 661a.
Tooth of same (X 3^) ; 662, Footprints of Chirotherium (X i'2) ; C63, Footprints of a turtle? .
Bayreuth, and in Upper Silesia. They are distinguished from the Enaliosaurs of
the Jurassic by the extraordinarily large temporal, orbitary, and nasal openings
through the cranium, which leave little bone. The NothuHonrus mirnhUis was
about seven feet long. The teeth were thin, long, and conical, three to five times
as long as broad, striated, slightly inflexed, and inserted in distinct cavities.
Placodus is another related genus. Two or three Plesiosaurs of the Lias (as
P. Hawkinsii and P. costatus) occur in the bone-bed at the very top of the TriaSj
Figs. 663 A, 663 B.
Fig. 663 A, Molar tooth of Microlestes antiquus, side-view; A', view of crown of same;
663 B, Myrmecobius fasciatus ( X ^ )ā¢
or base of the Lias, at Aust Cliff in England. Other Triassic Saurians are the
Belodon of von Mover (P/(j/?osoHrHS of Jager), a carnivorous, crocodile-like species,
438 MESOZOIC TIME REPTILIAN AGE.
with the teeth in sockets; and the Termatosaitrua of Flieninger, from the Keuper
of Wurtemberg.
(c.) Turtle!?. ā A series of tracks like fig. 663 have been observed in Germany
which have been referred to a Turtle, the earliest representative of the tribe.
The tracks form two distant parallel lines, as they should for an animal having
a broad shell-covered body and short legs.
Coprolites of Reptiles are also common. Various footprints are described
and named in Jardine's Ichnology of Annandale.
(d.) Mammals, ā Fig. 663 A represents the side-view of a tooth of Microlestcs
autiqitns Plieuinger, from the bone-breccia of Wurtemberg ; A', view of crown.
A tooth of the same mammal has been found at Frome, in England. Owen
regards the species as probably near the modern Mi/rmccohius and closely re-
lated to another extinct Marsupial genus, Playimdax, found in the English
Upper Oolite. Fig. 663 B represents the Myrmecohius fasciatus, a species of
Marsupial now living in Australia.
Fossils characteristic of the subdivisions of the Trias.
The characteristic fossils of the three subdivisions of the Trias
are as follow : ā
1. Loicer (jvoup. ā Voltzia heterojihylla, Calamites Monrjeoti, Placodus impressus,
Noihosaurns Sthimperi.
2. Jfiddle group. ā Encrinus lilii/ormis, Avicida f socialis (common to all the
groups), Mijoplioria (Trigonia) vulgaris, Jf. lineata, Terebratula vulgaris, Cera-
tites nodosus, Pemphix Sueurii, Hyhodus jifougeoti, Placodus (several species),
NotJiosaurus (species differing from those of the lower group), Simosaurns, Pisto-
eaurus.
3. Upper group, or Keuper, ā Equiseta, Calamites arenaceus, Pteropthyllum Jmjeri,
Pt. longifollum, Pt, Jfuusteri, Estheria (Posidonia) Keuperiana, Lahyrinthodon
giganteus, Belodon, Termutosaurus.
The Estheria minuta ranges through all the divisions.
rv. General Observations.
1. American.
General Progress. ā The following points bear upon the history of
this period : ā
T. The position of the rocks in linear ranges, parallel with the
mountains, and therefore along depressions in the surface tliat
were made when the Appalachian foldings took place. The Con-
necticut valley is one of the great synclinal depressions made at
that time. Such areas would naturally have become inlets of the
sea, or estuaries, river-courses, lakes, or marshes, and would have
received the debris of the hills brought in by streams.
II. The absence of Eadiates, the paucity of Mollusks, and the
TRIASSIC PERIOD. 489
presence of few species that are properly marine. These facts
prove that the ocean had imperfect access, where any, to the re-
gions, ā that the beds are not sea-shore formations like the Creta-
ceous and Tertiary of later times ; and thus they confirm the idea
that the beds are partly of estuary and partly of lacustrine origin.
The occurrence of vegetable remains and the coal beds sustain
this conclusion.
III. The ripple-marks, raindrop-impressions, and footprints.
These show, wherever they occur, that the layer vias for the time
a half-emerged mud or sand flat ; and, as they extend through
much of the rock, there is evidence that the layers in general
were not formed in deep water. They abound especially in the
upper half of the Connecticut-valley strata.
IV. The thickness, ā 3000 to 5000 feet or more. We learn from
this thickness, in connection with the preceding, that the areas
underwent a gradual subsidence of 3000 to 5000 feet or beyond ;
consequently, that these oblong depressions made at the time of
the foldings were slowly deepening, and continued to deepen until
the last layer was laid down.
V. The tilted and displaced condition of the beds, without evi-
dence of folds. This inclination has been attributed to deposition
on a sloping surface. But such cases of oblique deposition are
exceptions, and not the general rule ; while in the case of the
sandstone, the layers are inclined 10 to 30 degrees or more, in each
of the great regions. The tilting must, therefore, be a result of
mechanical force ; and, as faults are not numerous, while joints are
common, it follows that the force was very gradual in its action.
Under IV., a profound subsidence was shown to have been in
progress in the regions of depression occupied by the strata. Such
a subsidence would have brought a strain upon the overlying beds,
and sooner or later would have produced fractures and disturbance ;
and if one side or part of the depression were undergoing more
subsidence than the opposite, it would have caused that oblique
pushing of the beds that would have ended in faulting and tilting
them. The direction of the dip and strike in such a case would
depend on the relative positions, with reference to the \Vhole basin,
of the parts undergoing greatest and least subsidence.
VI. The sandstone strata intersected by dikes of trap. These
dikes are proofs of fracture of the earth's crust ; of more fractures
in the part of the crust directly beneath the formation than out-
side of the region ; therefore of fractures in the old synclinal
depression in progress of subsidence. The subsidence of such a
region would bring increasing tension or strain ui:>on the rocks
9
440 MESOZOIC TIME ā REPTILIAN AGE.
below, which might ultimate in fractures, especially about the
axis of the depression. The tilting, fractures, joints, and ejec-
tions of igneous rock are, therefore, parts of one connected series
of events.
The manner in which the trap at its eruption has sometimes
separated the layers of sandstone, and in this way escaped to the
surface, instead of coming up through the fissures simply, shows
that the rock had been tilted extensively before the ejection; and,
as the trap dikes intersect the later beds of the formation, the
igneous ejections were among the later results of the period, if not
to a great extent subsequent in time.
It is hence no mystery that rocks of igneous origin are intimately
associated with rocks of aqueous origin in these Triassic regions.
Thus the period of these rocks came to a close somewhat similar
to that of the Carboniferous age. The Carboniferous age ended
in a period of disturbance, escape of heat, as shown in consolida-
tions and metamorphism, and a comj^lete destruction of life along
the Continental border ; and the period of these sandstones was
closed in uplifts, fractures, emissions of heat, consolidations, and
destructions of life. But in the former case the crust was yield-
ing, and became folded into mountains : in the latter, the action,
though ranging along the same line of coast, from South Carolina to
Newfoundland, was more limited ; the stiffened crust only yielded
by breaking ; the heat came out in ejected melted rock, instead of
a slow, gentle effusion, and the swelling up of the lava and simj^le
tiltings of the strata formed hills and ridges. The destruction
of life was in both cases complete.
Life of the Period. ā The steps of progress in the life of the globe,
as the Mesozoic era opened in the Triassic period, were especially
important. The storing away as coal of the excess of atmospheric
carbon had purified the atmosphere; and soon after the close of
Palaeozoic time ā whose great feature was that its animal life had
made rocks, and its plants, coal ā we find higher races breathing
the better air. Saurians become numerous ; and the vertebrate
type expands by the appearance of the new classes Birds and
Mammals. Among these types, the Saurian continues rapidly to
rise in perfection with the following period of the age ; while the
birds and mammals remain of inferior types, forerunners of an
age of higher progress.
Geography/. ā The position of the Triassic beds on the Atlantic
border shows that this part of the continent stood nearly at its
present level. The strange absence of Atlantic sea-shore deposits
in the Triassic period may be accounted for by supposing that the
TRIASSIC PERIOD.
441
dry land stretched farther out to the eastward, and that the sea-
shore deposits were formed, but are now submerged. A change of
level of five hundred feet would take a breadth of eighty miles
from the ocean and add it to the continent.
This important fact ā which has been before referred to more than
once, on account of its bearing on the history of the continent ā
is presented to the eye in the accompanying map, copied from one
Fig. 664.
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2"
Map of the submerged border of the continent off New .Terse}- and Long Ishind, with lines
of equal soundings in fatlionis; NY, City of New York.
of the charts of the Coast Survey under Professor Bache. The
coast-line on the north is the south shore of Long Island ; that on
the west, the coast of New Jersey ; wliile the Bay of New York (at
the mouth of the Hudson) is near the junction of the two (below
NY). The dotted lines are lines of equal soundings, indicating
depths of 10, 20, 30, 40, 50, 60, 70, SO, 90, 100, 120 iathoms. These
lines run back in a long loop northwestward towards New York
442 MESOZOIC TIME REPTILIAN AGE.
harbor, showing deeper water along this line, and evidently
proving that once the land was above water, with the ifudson
River occupying this channel on its way to the ocean. At two or
three places along this channel there are "deep holes," as they
are called (one of them at 32, where the depth is thirty-two
f\\tlioms), which may have been former sites of New York harbor;
for the waters of the harbor are now about six fathoms deeper than
those about its entrance.
This border, now submerged, has, therefore, in former time been
dry land ; it may have been partly so in the Triassic period, and
thus have caused the imperfect connection of the Triassic areas of
the Atlantic border with the ocean.
The Triassic continent spread westward to Kansas, and south-
ward to Alabama ; for through this great area there are no rocks
more recent than the Palaeozoic.
The Triassic beds beyond the Mississippi are remarkable for
their great extent and their paucity of life. They occur in
western Kansas on the east, and along the Little Colorado west,
of the mountains ; and they have been observed at many points
between these distant meridians: it is therefore probable that
they cover a large part of the slopes of the mountains beneath
the Cretaceous and Tertiary rocks of the surface. The discovery
of animal fossils may yet be made in some part of this region.
Yet it is remarkable that the beds should have aflbrded thus far
no relics of marine life, unless the Saurian remains be an exception.
There appears to be but one mode of accounting for the forma-
tion of such deposits over this wide territory. The interior sea in
which the Carboniferous limestone of the preceding age ā even
wider in its limits ā had been formed, must have become more shal-
low and have been cut off to a great extent from free communica-
tion with the ocean. Such a shallow salt sea, alternately freshened
and concentrated by the successive rains and droughts of a season,
would be quite unfit for ordinary marine life. Few species could
survive through such alternations ; and hence there would be
necessarily a paucity of fossils in the deposits. Examples of such
interior salt seas without marine life now exist. Lake L'tah is one,
in the Rocky Mountains. A complete evaporation over any por-
tions would have deposited salt and gypsum, ā the salt to be dis-
solved and carried off wherever the region admitted of drainage
by outflowing waters, the gypsum to remain in the beds.
Facts observed among the Pacific Coral islands, illustrating the
destruction of life alluded to, have been mentioned on page 250.
These islands exemplify also the origiii of the gypsum. According
TRIASSIC PERIOD. 44;)
to A. Hague, there is a deposit of gypsum, two feet thick, on Jarvis
Island, overlying the coral sands of the old lagoon, and others
similar also on Starbuck's, McKean's, and Phoenix Islands. He
attributes the formation of the deposits to the repeated evapor-
ation of sea-water, long re-supplied by the tides, over the area of
the lagoon, during the time when it was gradually being recovered
from the ocean.
Climate. ā There are no data yet obtained for comparing the
climate of the Arctic in the Triassic period with that of the Tem-
perate United States.
In the preceding pages, the beds and the period they represent have been
called Tn'aseic. Yet it is to be understood that they are probably in part
Jurassic.
2. Foreign.
The occurrence of ripple-marks throughout most of the European
Triassic sandstones and marls, and also raindrop-impressions and
cracks from drying, show that the beds are of shallow-water and
mud-flat origin ; and the salt ā as explained on p. 249 ā indicates
that there were flats exposed to occasional inundations of the sea,
where the salt water evaporated. The kinds of rock are similar to
those of the Saliferous region in central New York, although they
belong to very different periods : the history of one is probably
essentially that of the other.
The fossiliferous limestone (Muschelkalk) of the Middle Trias
in Germany indicates that in that region there was for a while an
interval of somewhat deeper waters.
As the alternations in these beds depend on small changes
of level over limited areas, there is sufficient reason for their not
occurring in other regions.
Appendix. ā In Asia and Australia there arc coal beds of considerable extent,
which have been referred to different periods from the Carboniferous to the
Jurassic. The Asiatic deposits occur at Burdwan in western Bengal, where they
are extensively worked, and about Nagpur in the Deccan, India. In Austrnliii
they cover a large surface in New South Wales, extending inland from the
coast.
The fossil plants of the first region are species of Pecupterift, GloHsopten's (an
oblong simple-leaved fern). Taiiinpten'n. Vcrtehran'n (stems of unknown rela-
tions), Phjllotheca (of the Equisetum tribe), Zamifex, etc. About Nagpur nearly
the same genera and partly the same species occur, excepting the Cycads. In
the Australian beds there is a similar resemblance to the Burdwan coal field.
On account of the absence of the peculiarly Carboniferous genera in both
the Asiatic and Australian beds, and the general similarity of their flora, while
444 MESOZOIC TIME REPTILIAN AGE.
at the same time the Bengal beds contain Cycads, the coal has been referred by
most authors to the Mesozoic, and either the Jurassic or Triassic period.
In the Australian beds there are heterocercal Ganoids ; and hence the forma-
tion cannot be more recent than the Triassic* Sixty miles south of Nagpur, at
Mangali, beds similar to those of Nagpur occur, which have been referred to the
same period, although there are no plants to demonstrate positive identity ; they
contain Estherias, homocercal Ganoich, and a species of Lahijrinthodont, ā evi-
dently a Triassic assemblage of species.
In view of all the facts, it appears probable that the coal beds referred to, both
in Asia and Australia, represent the Triassic period.
There are other beds at Kota on the Pranhita, related to those of Mangali.
There are still others at the Kajmahal Hills, in central India, the age of which
is more doubtful. They abound in Cycads, and fail of most of the genera
found at Nagpur : they have been regarded as Jurassic.
JURASSIC PERIOD (17).
The Jurassic period derives its name from the Jura Mountains
on the western borders of Switzerland, one of the regions charac- Ā«
terized by the formation.
1. AMERICAN.
I. Rocks : kinds and distribution.
On the Atlantic border, the upper portion of the formation
described in the preceding pages on the Triassic may belong, as
has been observed, to the Jurassic period. As no species of fossils
characteristic of any part of this period have yet been found in
the beds, there is some doubt on this point. The absence of Tri-
gonias, Belemnitcs, Ammonites, and other Jurassic forms, may, however,
be owing to the fact that the strata are not properly of sea-shore
origin.
On the Gidf border there are no rocks of this period anywhere
exposed to view.
* The author, in his notes on Australian Geology, published in his Explor-
ing Expedition Geological Report (in which one of the Ganoids and many of
the coal plants are figured and described), referred the Australian beds to
the Permian period, on account of the presence of the heterocercal Ganoids, the
absence of Cycads, and the regular continuity of the beds with the Carboniferous
strata below. But the resemblance to the Indian flora must bring all to one
horizon, and the above conclusion seems best to harmonize the facts. Rev. W.
B. Clarke reports true Lepidodendra from the interior of New South Wales, ā
from which it appears that the Carboniferous flora is represented on the Austra-
lian continent.
JURASSIC PERIOD. 445
> In the Western Interior region, the Jurassic period may claim a part
ā perhaps a large part ā of the gypsiferous beds already described:
here, again, fossils are wanting to decide the question of age.
But, apart from these doubtful beds, there are true Jurassic strata
full of fossils, overlying in many places the gypsiferous marls and
sandstone. They have been observed about the Black Hills and
the Laramie Mountains, and also at the base of other ridges in the
Rocky Mountains. The beds consist of impure limestone with
layers of marl.
In the A7'ciic region, also, there are a number of localities of fossili-
ferous Jurassic strata.
The discovery and identification of the Jurassic of the Black Hills af Dakota
were made by Hayden & Meek. The rocks occur also at Red Buttes on the
North Platte, west of the Black Hills; also along the southwest side of the
Big Horn Mountains (43.^Ā° N., 108Ā° W.), and the northeast side of the Wind River
Mountains; also beyond the Wind River Mountains, on the west; also about
the head-waters of the Missouri : ā at all of which places fossils occur. (Hayden.)
Another locality is near the valley of Green River, east of Lake Utah (Great
Salt Lake), as announced by Meek & Engelmann.
The rocks observed are in general a gray or whitish marly or arenaceous
limestone, with occasional purer compact limestone beds, intercalated with
laminated marls. The thickness at the Black Hills is about 200 feet ; on the
northeast of the Wind River Mountains, SCO to 1000 feet; about Long's Peak,
where the marls are absent, 50 to 100 feet.
The Arctic localities are ā the eastern shores of Prince Patrick's Land, in 76Ā°
20' N., 117Ā° 20' W. ; the islands Exmouth and Talbe, north of Grinnell Land,
77Ā° 10' N., 95Ā° W. ; and Katmai Bay, or Cook's Inlet, in Northwest America,
60Ā° N., 151Ā° W. '
II. Life.
Although but little is yet known of the life in America of the
Jurassic period, several genera of Radiates and MoUusks which
mark the Jurassic beds of Europe have here been found, the most
prominent of which are Pentacrinus, Trigonia, Ammonites, and Be-
lemnites. The characteristics of Belemnites and Ammonites are
briefly mentioned on p. 156, and again beyond, on pp. 450, 451.
Characteristic Species.
No plants have been described, except a few by Newberry from a coal seam in
the gypsiferous sandstone of the Upper Colorado, in the Moqui country (near
the meridian of 111Ā°), the age of which is doubtful (p. 417). The observed
genera are Ci/clopteris, Pecoiiteris, Neuropteris, Spheuopten's, and Clathropteris.
The Clathropieris from near the middle of the Connecticut River sandstone
(fig. 628, p. 419), as suggested by Hitchcock, is some evidence ā though far from
446
MESOZOIC TIME ā REPTILIAN AGE.
decisive ā for referring the upper half of that formation to the Jurassic. The
European species of this genus occur in the Lias and Trias.
The species of Radiates and Mollusks here figured were collected at the Black
Hills.
1. Radiates. ā Fig. 665, a joint of the stem of Pentacrinus Asteriscus, a
Trinoid with a pentagonal column.
2. Mollusks. ā (Ā«.) Conchifers. ā Fig. 666, 3Ionotis cnrta ; fig. 667, Tn'gonia
L'onradi ; 068, Tancredia Warreniana. (b.) Cejyhalojyods. ā Fig. 669, young spe-
Figs. 665-670.
Fig. 665, A segment of the column of Pentacrinus asteriscus; 666, Monotis carta; 667, Tri-
gonia Conradi ; 668, Tancredia Warreniana; 669, Ammonites cordiformis ; 669 a, Side-view
of same, a little reduced ; 670, Belemnites densus.
cimen of Ammonites cordiformis; fig. 669 a, side-view of the same; fig. 670,
Belemnites densus, the upper part broken away.
Among the Arctic fossils of this period, there are at Prince Patrick's Land