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INTRODUCTION AND SUCCESSION

OP

VERTEBRATE LIFE IN AMERICA

A1ST ADDRESS

DELIVERED BEFORE THE

AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE,

AT NASHVILLE, TENN., AUGUST 30, 1877,

BY

Professor 0. C. MARSH,

Vice President.

Tuttle, Morehouse & Taylor, Printers, New Haven, Conn.

INTRODUCTION AND SUCCESSION OF VERTEBRATE

LIFE IN AMERICA.

-*"♦"♦-

The origin of life, and the order of succession in which its
various forms have appeared upon the earth, offer to science
its most inviting and most difficult field of research.
Although the primal origin of life is unknown, and may per-
haps never be known, yet no one has a right to say how much
of the mystery now surrounding it science cannot remove.
It is certainly within the domain of science to determine when
the earth was first fitted to receive life, and in what form the
earliest life began. To trace that life in its manifold changes
through past ages to the present is a more difficult task, but
one from which modern science does not shrink. In this wide
field, every earnest effort will meet some degree of success ;
every year will add new and important facts ; and every
generation will bring to light some law, in accordance with
which ancient life has been changed into life as we see it
around us to-day. That such a development has taken place,
no one will doubt who has carefully traced any single group
of animals through its past history, as recorded in the crust of
the earth. The evidence will be especially conclusive, if the
group selected belongs to the higher forms of life, which are
sensitive to every change in their surroundings. But I am sure
I need offer here no argument for evolution ; since to doubt
evolution to-day is to doubt science, and science is only another
name for truth.

Taking, then, evolution as a key to the mysteries of past life
on the earth, I invite your attention to the subject I have
chosen : The Introduction and Succession of Vertebrate
Life in America.

In the brief hour allotted to me, I could hardly hope to give
more than a very incomplete sketch of what is now known on
this subject. I shall, therefore, pass rapidly over the lower
groups, and speak more particularly of the higher vertebrates,
which have an especial interest to us all, in so far as they
approach man in structure, and thus indicate his probable
origin. These higher vertebrates, moreover, are most important
witnesses of the past, since their superior organization made
them ready victims to slight climatic changes, which would
otherwise have remained unrecorded.

In considering the ancient life of America, it is important to
bear in mind that I can only offer you a brief record of a few
of the countless forms that once occupied this continent. The
review I can bring before you will not be like that of a great
army, when regiment after regiment with full ranks moves by
in orderly succession, until the entire host has passed. My
review must be more like the roll-call after a battle, when only
a few scarred and crippled veterans remain to answer to their
names. Or rather, it must resemble an array of relics, dug
from the field of some old Trojan combat, long after the con-
test, when no survivor remains to tell the tale of the strife.
From such an ancient battle-field, a Schliemann might unearth
together the bronze shield, lance-head, and gilded helmet of a
prehistoric leader, and learn from them with certainty his race
and rank. Perhaps the skull might still retain the barbaric
stone weapon by which his northern foe had slain him. Near
by, the explorer might bring to light the commingled coat of
mail and trappings of a horse and rider, so strangely different
from the equipment of the chief, as to suggest a foreign ally.
From these, and from the more common implements of war
that fill the soil, the antiquary could determine, by patient
study, what nations fought, and, perhaps, when, and why.

By this same method of research, the more ancient strata
of the earth have been explored, and, in our Western wilds,
veritable battle-fields, strown with the fossil skeletons of the
slain, and guarded faithfully by savage superstition, have been
despoiled, yielding to science treasures more rare than bronze
or gold. Without such spoils, from many fields, I could not
have chosen the present theme for my address to-night.

According to present knowledge, no vertebrate life is known
to have existed on this continent in the Archaean, Cambrian, or
Silurian periods ; yet during this time, more than half of the
thickness of American stratified rocks was deposited. It by
no means follows that vertebrate animals of some kind did not
exist here in those remote ages. Fishes are known from the
Upper Silurian of Europe, and there is every probability that
they will yet be discovered in our strata of the same age, if not
at a still lower horizon.

In the shore deposits of the early Devonian sea, known as
the Schoharie Grit, characteristic remains of Fishes were pre-
served, and in the deeper sea that followed, in which' the
Corniferous limestone was laid down, this class was well
represented. During the remainder of the Devonian, Fishes
continue abundant in the shallower seas, and, so far as now
known, were the only type of vertebrate life. (These fishes
were mainly Ganoids, a group, represented in our present
waters by the Gar-pike (Lepidosteus) and Sturgeon (Acipenser),
but, in the Devonian sea, chiefly by the Placoderms, the exact
affinities of which are somewhat in doubt. ) With these were
Elasmobranchs, or the Shark tribe, and among them a few
Chimasroids, a peculiar type, of which one or two members still
survive. The Placoderms were the monarchs of the ocean. All
were well protected by a massive coat of armor, and some of
them attained huge dimensions. The American Devonian fishes
now known are not as numerous as those of Europe, but they
were larger in size, and mostly inhabitants of the open sea.
Some twenty genera and forty species have been described.

6

The more important genera of Placoderms are, Dinicldhys,
Aspidichthys, and Diplognathus, our largest Palaeozoic fishes.
Others are, Acanthaspis, Acantholepis, Coccosteus, Macropetalich-
tltys, and Onychodus. Among the Elasmobranchs were, Clado-
dus, Clenacanthus, Afachceraca?ithus, Rhynchodus, and Ptyclodus,
the last two being regarded as Obimseroids. In the Chemung
epoch, the great Dipterian family was introduced with Dipterus,
Heliodus, and possibly Ceratodus. Species of the European
genera, Boihriolepis "and Holoplychius, have likewise been found
in our Devonian deposits.

I With the close of the Devonian, came the almost total extinc-
tion of the great group of Placoderms, while the Elasmobranchs,
which had hitherto occupied a subordinate position, increase in
numbers and size, and appear to be represented by Sharks,
Rays, and Chimasras.' Among the members of this group from
the Carboniferous, were numerous Cestracionts, species of
Cochliodus of large size, with others of the genera Deltodus,
Ilelodus, Psammodus and Sandalodus. Of the Petalodonts,
there were Antliodus, Chomatodus, Ctenoptychius, Petalodus and
Petalorhynchus ; and of the Hybodonts, the genera Cladodus,
Carcharopsis and Diplodus. These Elasmobranchs were the
rulers of the Carboniferous open sea, and more than one hun-
dred species have been found in the lower part of this forma-
tion alone. The Ganoids, although still abundant, were of
smaller size, and denizens of the more shallow and confined
waters. The latter group of fishes was represented by true
Lcpidostidre, of the genera Palceoniscus, Amblypterus, Platyso-
mus and Eurylepis. Other genera are, Phizodus, Megalichthys,
Ctenodus, Pdeslus, Orodus, Ctenacandius, GyracanthitsA and Ccela-
canthus. Most of these genera occur also in Europe.-

From the Permian rocks of America, no vertebrate remains
are known, although in the same formation of Europe Ganoids
are abundant; and with them are remains of Sharks, and some
other fishes, the affinities of which are doubtful. The Palaeo-
zoic fishes at present known from this country are quite as
numerous as those found in Europe.

(jn the Mesozoic age, the Fishes of America begin to show a
decided approach to those of our present waters.,) From the
Triassic rocks, Ganoids only are known, and they are all more
or less closely related to the modern Gar-pike, or Lepidosteus.
They are of small size, and the number of individuals
preserved is very large. The characteristic genera are, Catop-
terus, Ischypterus, Ptycholepis, Wmbdolepis, and Turseodus.
From the Jurassic deposits, no remains of fishes are known,
but in the Cretaceous, ichthyic life assumed many and
various forms; and the first representatives of the Teleosts,
or bony fishes, the characteristic fishes of to-day, make
their appearance. In the deep open sea of this age, Elas-
mobranchs were the prevailing forms, Sharks and Chimreroids
being most numerous. In the great inland Cretaceous sea of
North America, true osseous fishes were most abundant, and
among them were some of carnivorous habits, and immense
size. The more sheltered bays and rivers were shared by the
Ganoids and Teleosts, as their remains testify. The more
common genera of Cretaceous Elasmobranchs were, Otodus,
Oxyrhina, Galeocerdo, Lamina and Ptychodus. Among the
osseous fishes, Beryx, Enchodus, Portheus and Saurocephalus
were especially common, while the most important genus of
Ganoids was Lepidolus.

The Tertiary fishes are nearly all of modern types, and from
the beginning of this period there was comparatively little
change. ) In the marine beds, Sharks, Rays and Chimseroids
maintained their supremacy, although Teleosts were abundant,
and many of them of large size. The Ganoids were compara-
tively few in number. In the earliest Eocene fresh-water
deposits, it is interesting to find that the modern Gar-pike,
and Amia, the Dog- fish of our western lakes, which by their
structure are seen to be remnants of a very early type, are
well represented by species so closely allied to them that only
an anatomist could separate the ancient from the modern/ In
the succeeding beds, these fishes are still abundant, and with
them are Siluroids nearly related to the modern Cat-fish

(Pimelodus). Many small fishes, allied apparently to the
modern herring (Olupea), left their remains in great numbers
in the same deposits, and, with them has been recently found
a land-locked Ray (Heliobatis).

The almost total absence of remains of fishes from the Mio-
cene lake-basins of the West is a remarkable fact, and perhaps
may best be explained by the theory that these inland waters,
like many of the smaller lakes in the same region to-day, were
so impregnated with mineral matters as to render the existence
of vertebrate life in them impossible. No one who has tasted
such waters, or has attempted to ford one of the modern alkaline
lakes which are often met with on the present surface of the
same deposits, will doubt the efficiency of this cause, or the
easy entombment of the higher vertebrates that ventured within
their borders. Tn the Pliocene lake-basins of the same region,
remains of fishes were not uncommon, and in some of them are
very numerous. These are all of modern types, and most of
them are Cyprinoids, related to the modern Carp. The Post-
pliocene fishes are essentially those of to-day.

In this brief synopsis of the past ichthyic life of this Conti-
nent, I have mentioned only a few of the more important facts,
but sufficient, I trust, to give an outline of its history. Of this
history, it is evident that we have as yet only a very imperfect
record. We have seen that the earliest remains of fishes
known in this country, are from the lower Devonian ; but these
old fishes show so great a diversity of form and structure, as
to clearly indicate for the class a much earlier origin. In this
connection, we must bear in mind that the two lowest groups
of existing fishes are entirely without osseous skeletons, and
hence, however abundant, would leave no permanent record in
the deposits in which remains of fishes are usually preserved.
It is safe to infer, from the knowledge which we now possess
of the simpler forms of life, that even more of the early fishes
were cartilaginous, or so destitute of hard parts as to leave no
enduring traces of their existence. Without positive knowledge
of such forms, and considering the great diversity of those we

9

have, it would seem a hopeless task at present to attempt
to trace successfully the genealogy of this class. 'One line,
however, appears to be direct, from our modern Gar-pike,
through the lower Eocene Lepidosteus to the Lepidotus of the
Cretaceous, and perhaps on through the Triassic Ischypterus
and Carboniferous Pakeoniscus ; but beyond this, in our rocks,
it is lost.) The living Chimaera of our Pacific coast has nearly
allied forms in the Tertiary and Cretaceous, more distant rela-
tives in the Carboniferous, and a possible ancestor in the
Devonian Rhynchodus. Our Sharks likewise can be traced
with some certainty back to the Palaeozoic ; and even the
Lepidosireji, of South America, although its immediate pre-
decessors are unknown, has some peculiar characters which
strongly point to a Devonian ancestry. These suggestive lines
indicate a rich field for investigation in the ancient life-history
of American fishes.

The Amphibians, the next higher class of vertebrates, are so
closely related to the fishes in structure, that some peculiar
forms of the latter have been considered by anatomists as
belonging to this group. The earliest evidence of Amphibian
existence, on this continent, is in the Sub-Carboniferous, where
foot-prints have been found which were probably made by
Labyrinthodonts, the most ancient representatives of the class.
Well preserved remains are abundant in the Coal Measures,
and show that the Labyrinthodonts differed in important par-
ticulars from all modern Amphibians, the group which includes
our frogs and salamanders. Some of these ancient animals
resembled a salamander in shape, while others were serpenvt-like
in form. None of those yet discovered were frog-like, or without
a tail, although the restored Labyrinthodont of the text books
is thus represented. All were protected by large pectoral
bony plates, and an armor of small scutes on the ventral surface
of the body. The walls of their teeth were more or less folded
whence the name Labyrinthodont. The American Amphib-
ians known from osseous remains are all of moderate size,
but the foot-prints attributed to this group indicate animals

2

10

larger than any of the class yet found in the old world. The
Carboniferous Amphibians were abundant in the swampy trop-
ical forests of that period, and their remains have been found
imbedded in the coal then deposited, as well as in hollow
stumps of the trees left standing.

The principal genera of this group from American Car-
boniferous rocks, are, Sauropus, known only from footprints,
Baphetes, Dendrerpeton, Hylonomus, Rylerpeton, Raniceps, Pelion,
Leptophr actus, Molgophis, Plyonius, Amphibamus, Cocytinus, and
Ceraterpeton. The last genus occurs also in Europe. Certain of
these genera have been considered by some writers to be more
nearly related to the Lizards, among true reptiles. Some other
genera known from fragmentary remains or footprints in this
formation have likewise been referred to the true reptiles, but
this question can perhaps be settled only by future discoveries.

No Amphibia are known from American Permian strata, but
in the Triassic, a few characteristic remains have been found.
The three genera, Dictyocephalus, Dispelor and Pariostegus, have
been described, but, although apparently all Labyrintho-
donts, the remains preserved are not sufficient to add much to
our knowledge of the group. The Triassic foot-prints which
have been attributed to Amphibians are still more unsatis-
factory, and at present no important conclusions in regard to
this class can be based upon them. From the Jurassic and
Cretaceous beds of this Continent, no remains of Amphibians
are known. A few only have been found in the Tertiary,
and these are all of modern types.

(The Amphibia are so nearly allied to the Ganoid fishes, that
we can hardly doubt their descent from some member of that
group. With our present limited knowledge of the extinct
forms, however, it would be unprofitable to attempt to trace in
detail their probable genealogy. )

The authors to whom especial credit is due for oar knowl-
edge of American fossil Fishes and Amphibians, are New-
berry, Leidy, Cope, Dawson, Agassiz, St. John, Gribbes, Wy-
man, Redfield, and Emmons, and the principal literature of the
subject will be found in their publications.

11

.Reptiles and Birds form the next great division of ver-
tebrates, the Sauropsida, and of these the Reptiles are the older
type, and may be first considered. { While it may be stated
with certainty that there is at present no evidence of the exist-
ence of this group in American rocks older than the Car-
boniferous, there is some doubt in regard to their appearance
even in this period.) Various foot-prints which strongly resem-
ble those made by Lizards ; a few well preserved remains similar
to the corresponding bones in that group ; and a few charac-
teristic specimens, nearly identical with those from another
order of this class, are known from American Coal Measures.
These facts, and some others which point in the same direction,
render it probable that we may soon have conclusive evidence of
the presence of true Reptiles in this formation, and in our over-
lying Permian, which is essentially a part of the same series.
In the Permian rocks of Europe, true Reptiles have been
found.

The Mesozoic Period has been called the Age of Reptiles,
and during its continuance some of the strangest forms of rep-
tilian life made their appearance, and became extinct. Near
its commencement, while the Triassic shales and sandstones
were being deposited, true reptiles were abundant. Among
the most characteristic remains discovered are those of the
genus Belodon, which is well known also in the Trias of
Europe. It belongs to the Thecodont division of Reptiles,
which have teeth in distinct sockets, and its nearest affinities
are with the Crocodilia, of which order it may be considered
the oldest known representative. In the same strata in which
the Belodonts occur, remains of Dinosaurs are found, and it is
a most interesting fact that these highest of reptiles should make
their appearance, even in a generalized form, at this stage of
the earth's history. The Dinosaurs, although true reptiles in
all their more important characters, show certain well marked
points of resemblance to existing birds of the order Eatiice, a
group which includes the Ostriches; and it is not improbable
that they were the parent stock from which birds originated.

12

During Triassic time, the Dinosaurs attained in America an
enormous development both in variety of forms and in size.
Although comparatively few of their bones have as yet
been discovered in the rocks of this country, they have left
unmistakable evidence of their presence in the foot-prints and
other impressions upon the shores of the waters which they
frequented. The Triassic sandstone of the Connecticut Valley
has long been famous for its fossil foot-prints, especially the
so-called "bird-tracks," which are generally supposed to have
been made by birds, the tracks of which many of them closely
resemble. A careful investigation, however, of nearly all the
specimens yet discovered, has convinced me that there is not a
particle of evidence that any of these fossil impressions were
made by birds. Most of these three-toed tracks were certainly
not made by birds ; but by quadrupeds, which usually walked
upon their hind feet alone, and only occasionally put to the
ground their smaller anterior extremities. I have myself
detected the impressions of these anterior limbs in connection
with the posterior foot-prints of nearly all of the supposed
" bird-tracks" described, and have little doubt that they will
eventually be found with all. These double impressions are
precisely the kind which Dinosaurian reptiles would make,
and as the only characteristic bones yet found in the same
rocks belong to animals of this group, it is but fair to attribute
all these foot-prints to Dinosaurs, even where no impressions
of fore-feet have been detected, until some evidence appears
that they were made by Birds. I have no doubt that
Birds existed at this time, although at present the proof is
wanting.

The principal genera of Triassic Eeptiles known from osseous
remains in this country are, Amjjhisaurus (Megadactyhis),
from the Connecticut Valley, Bathygnathus, from Prince Ed-
ward's Island, Belodon and Clepsysaurus. Other generic names
which have been applied to foot-prints and to fragmentary
remains, need not be here enumerated. A few remains of
Eeptiles have been found in undoubted Jurassic rocks of

13

America, but they are not sufficiently well determined to be
of service in this connection. Others have been reported from
supposed Jurassic strata, which are now known to be Creta-
ceous. ( It will thus be seen that, although reptilian life was
especially abundant during the Triassic and Jurassic periods,
but few bones have been found. This is owing in part to the
character of most of the rocks then formed, which were not
well fitted for preserving such remains, although admirably
adapted to retain foot-prints.

During the Cretaceous Period, Reptilian life in America
attained its greatest development, and the sediments laid down
in the open seas and estuaries were usually most favorable for
the preservation of a faithful record of its various phases. With-
out such a perfect matrix as some of these deposits afford, many
of the most interesting vertebrates recently brought to light
from this formation would probably have remained unknown.
The vast extent of these beds ensures, moreover, many future
discoveries of interest.

In the lowest Cretaceous strata of the Rocky Mountain
region, the Dakota group, part of which at least represents
the Wealden of Europe, remains of Chelonia, or Turtles, Croc-
odiles, and Dinosaurs occur, the last being especially abun-
dant. The Chelonia, although known from the Jurassic of
Europe, here appear for the first time in American rocks.
Some of the earliest forms are allied to the modern genus
Trionyx. In the higher Cretaceous beds, some Chelonians of
enormous size have been found. They belong to the genus
Atlantochelys, which has the ribs separate, as in the existing
Sphargis, and presents other embryonic characters. A few
genera appear to be related to the modern genus Chelone. The
remaining Cretaceous species were mostly of the Emydoid
type ; and others were related to Chelydra. The more important
genera of Cretaceous Chelonians known from characteristic speci-
mens are, Atlantochelys {Protostega), Adocus, Bothremys, Compse-
mys, Plastomenus, Osteopygis, Propleura, Lytoloma, and Taphros-
phys. Most of these genera were represented by several species,

14

and the individuals were numerous. No land Tortoises have as
yet been found in this formation. In American Tertiary depos-
its, Chelonians are abundant, especially in the fresh-water beds.
They all show near affinities with modern types, and most of
them can be referred to existing genera. In the Tertiary lake-
basins of the West, land Tortoises are very numerous, and
with them are many fresh-water forms of Trionyx and allied
genera.

A striking feature of the American Cretaceous fauna, as con-
trasted with that of Europe, is the almost entire absence in our
strata of species of Ichthyosaurus and Plesiosaurus, which
abound in many other regions, but here seem to be replaced by
the Mosasaurs. ) A few fragmentary remains have indeed been
referred to these genera, but the determination may fairly be
questioned. This is more than true of the proposed new order
Streptosauria, which was founded wholly on error. The order
Plesiosauria, however, is well represented, but mainly by forms
more nearly related to the genus Pliosaurus than to the type
of the group. These were marine reptiles, all of large size,
while some of them attained vast dimensions. So far as at
present identified, they may be referred to the genera, Cimolio-
saurus, Discosaurus (JElasmosaurus), and Pliosaurus. The num-
ber of species is comparatively few, and none are known above
the Cretaceous. The important suggestion of Gegenbaur, that
the Halisauria, which include the Plesiosaurs, branched off
from the Fishes before the Amphibians, finds some support in
American specimens recently discovered.

The Eeptiles most characteristic of our American Cretaceous
strata are the Mosasauria, a group with very few representatives
in other parts of the world. In our Cretaceous seas, they ruled
supreme, as their numbers, size, and carnivorous habits, enabled
them to easily vanquish all rivals. Some we're at least sixty
feet in length, and the smallest ten or twelve. In the inland
Cretaceous sea from which the Rocky Mountains were begin-
ning to emerge, these ancient " Sea Serpents" abounded ; and
many were entombed in its muddy bottom. On one occasion,

15

as I rode through a valley washed out of this old ocean bed, I
saw no less than seven different skeletons of these monsters in
sight at once. The Mosasaurs were essentially swimming Liz-
ards, with four well developed paddles, and they had little affin-
ity with modern serpents, to which they have been compared.
The species are quite numerous, but they belong to compara-
tively few genera, of which Mosasaurus, Tylosaurus, Lestosaurus
and Edestosaurus, have alone been identified with certaintj7. The
genus Mosasaurus was first found in Europe. All the known
species of the group are Cretaceous.

The Crocodilia are abundant in rocks of Cretaceous age in
America, and two distinct types are represented. The older
type, which is foreshadowed by Belodon of the Trias, has bicon-
cave vertebra?, and shows marked affinities with the genus
Teleosaurus, from the Jura of Europe. The best known
genus is Hyposaurus, of which there are several species, all
more or less resembling in form the modern Gavial of the
Ganges. , A peculiar intermediate form is seen in Dijylosaurus,
from the Wealden of the Rocky Mountains. / The second type,
which now makes its appearance for the first time, has pro-
ccelian vertebrae, and in other respects resembles existing Croc-
odiles. The genera described are Bottosaurus, Holops and Tho-
racosaurus) none of which, so far as known, pass above the
Cretaceous. Of Crocodilia with opisthoccelous vertebrae, Amer-
ica, so far as we know, has none. Specimens similar to those
so termed in Europe, are not uncommon here, but they per-
tain to Dinosaurs.

In the Eocene fresh-water beds of the West, Crocodilians
are especially abundant, and all, with the exception of Limno-
sawus, belong apparently to the genus Crocodilus, although
some species show certain points of resemblance to existing
Alligators. The Miocene lake-basins of the same region
contain no remains of Crocodiles, so far as known, and the
Pliocene deposits have afforded only a single species. The
Tertiary marine beds of the Atlantic Coast contain com-
paratively few Crocodilian remains, and all are of modern

16

types; the genus Gaviab's having one Eocene species, and the
Alligator being represented only in the latest deposits.

It is worthy of special mention in this connection, that no
true Lacertilia, or Lizards, and no Ophidia, or Serpents, have
yet been' detected in American Cretaceous beds; although their
remains, if present, would hardly have escaped observation in
the regions explored. The former will doubtless be found, as
several species occur in the Mesozoic of Europe ; and perhaps
the latter, although the Ophidians are apparently a more mod-
ern type, (in the Eocene lake-basins of Western America, re-
mains of Lizards are very numerous, and indicate species much
larger than any existing to-day. Some of these, the Olyplosau-
ridce, were protected by a highly ornamented bony coat of mail,
and others were covered with scales, like recent Lizards. A
few resembled, in their more important characters, the modern
Iguana. The genera best represented in the Eocene, are, Olyp-
tosaurus. Iguanavus, Oreosaurus, Thinosaurus, Tinosaurus and
Saniva. i Some of these genera appear to have continued into the
Miocene, but here, as well as in the Pliocene, few remains of
this group have been found. It is not improbable that some
of our extinct Eeptiles may prove to belong to Rynchocephala,
but at present this is uncertain. The genus Notosaurus, from
Brazil, has biconcave vertebras, and some other characters
which point to that group. No Dicynodonts or Thecodonts
have as yet been found in this country.

The first American Serpents, so far as now known, appear
in the Eocene, which contains also the oldest European species.
On the Atlantic border, the genus Titqnophis (Dinophis) is
represented by several species of large size, one at least thirty
feet in length, and all doubtless inhabitants of the sea. In the
fresh-water Western Eocene, remains of snakes are abundant,
but all are of moderate size. The largest of these were related
to the modern Boa Constrictors. The genera described are
Boavus, Lithophis and Limnophis. The Miocene and Pliocene
Snakes from the same region are known only from a few frag-
mentary remains.

17

The Pterosauria, or flying Lizards, are among the most
interesting Reptiles of Mesozoic time, and many of them left
their remains in the soft sediments of our inland Cretaceous
sea. These were veritable Dragons, having a spread of wings
of from ten to twenty-five feet. They differed essentially from
the smaller Pterodactyls found in the old world, in the entire
absence of teeth, showing in this respect a resemblance to
modern birds ; and they possess other distinctive characters.
They have therefore been placed in a new order, Pteranodoniia,
from the typical genus Pteranodo?i, of which five species are
known. The only other genus is Nyctosaurus, represented by a
single species. All the specimens yet found are from essen-
tially the same horizon, in the Chalk of Kansas. The reported
discovery of remains of this order from older formations in this
country is without foundation.

[ The strange Reptiles known as Dinosauria, which, as we
have seen, were numerous during the deposition of our Triassic
shales and sandstones, have not yet been found in American
Jurassic, but were well represented here throughout the Cre-
taceous, and at its close became extinct. These animals possess
a peculiar interest to the anatomist, since, although reptilian
in all their main characters, they show clear affinities with
the Birds, and have some features which may point to Mammals.
The Cretaceous Dinosaurs were all of large size, and most of
them walked on the hind feet alone, like modern Struthious
birds. Two well marked types may be distinguished among
the remains discovered in deposits of this age : the herbiv-
orous forms, represented mainly by Hadrosaurus, a near ally of
the Iguanodon of Europe; and their carnivorous enemies, of
which Dryptosaurus (Lcelaps) may be considered typical in this
country, and Megalosaurus in Europe. Near the base of our
Cretaceous formation, in beds which I regard as the equivalent
of the European Wealden, the most gigantic forms of this
order yet discovered have recently been brought to light. One
of these monsters (Titanosaurus montanus), from Colorado, is
by far the largest land animal yet discovered ; its dimensions

3

18

being greater than was supposed possible, in an animal that
lived and moved upon the land. It was some fifty or sixty
feet in length, and, when erect, at least thirty feet iu height.
It doubtless fed upon the foliage of the mountain forests,
portions of which are preserved with its remains. With Titan-
osaurus, the bones of smaller Dinosaurs, one (Najiosaurus) not
larger than a Cat, as well as those of Crocodiles and Turtles,
are not uncommon. \The recent discovery of these interesting
remains, many and various, in strata that had long been pro-
nounced by professional explorers barren of vertebrate fossils,
should teach caution to those who decline to accept the imper-
fection of our knowledge to-day as a fair plea for the supposed
absence of intermediate forms^

In the marine Cretaceous beds of the West, only a single
Dinosaur (Hadrosaurus agilis), has been found, but in the higher
fresh-water beds, which mark the close of this formation, their
remains are numerous, and indicate several well marked species,
if not genera. In the marine beds on the Atlantic Coast, the
bones of Dinosaurs are frequently met with, and in the Upper
Cretaceous Greensand of New Jersey, the type specimens of
Hadrosaurus and Dryptosaurus were found. In Cretaceous
fresh-water deposits on the coast of Brazil, remains of this order
occur, but the specimens hitherto discovered are not sufficiently
characteristic for accurate determination. This is unfortunately
true of many Dinosaurian fossils from North America, but the
great number of these Reptiles which lived here during the
Cretaceous Period promises many future discoveries, and sub-
stantial additions to our present knowledge of the group.

The first appearance of Birds in America, according to our
present knowledge, was during the Cretaceous Period, although
many announcements have been made of their existence in
preceding epochs. The evidence of their presence in the Trias,
based on footprints and other impressions, is, at present, as we
have seen, without value; although we may confidently await
their discovery there, if not in older formations. ArchceojJtej-yx,
from the European Jura, the oldest bird known, and now

19

fortunately represented by more than a single specimen,
clearly indicates a much higher antiquity for the class. The
earliest American forms, at present known, are the Odontornithes,
or Birds with teeth, which have been exhumed within the last
few years, from the Chalk of Kansas. The two genera, Hes-
perornis and Ichihyornis, are types of distinct orders, and differ
from each other and from Archceopteryx much more than do
any existing birds among themselves; thus showing that Birds
are now a closed type, and that the key to the history of the
class must be sought for in the distant past.

In Hesperornis, we have a large aquatic bird, nearly six feet
in length, with a strange combination of characters. The jaws
are provided with teeth, set in grooves ; the wings were rudi-
mentary, and useless ; while the legs were very similar to those
of modern diving birds. This last feature was merely an adap-
tation, as the more important characters are Struthious, showing
that Hesperornis was essentially a carnivorous swimming Ostrich.
Ichthyornis, a small flying bird, was stranger still, as the teeth
were in sockets; and the vertebrae biconcave, as in Fishes,
and a few Keptiles. Apatornis and other allied forms occur
in the same beds, and probably all were provided with teeth.
It is strange that the companions of these ancient toothed
Birds should have been Pterodactyls without teeth. In the
later Cretaceous beds of the Atlantic Coast, various remains
of aquatic Birds have been found, but all are apparently dis-
tinct from those of the West. The known genera of Ameri-
can Cretaceous birds are, Apatornis, Baptornis, Graculavus,
Hesperornis, Ichthyornis, Laornis, Lestornis, Paloeotringa and
Telmatornis. These are represented by some twenty species.
In Europe, but two species of Cretaceous birds are known,
and both are based upon fragmentary specimens.
(During the Tertiary period, Birds were numerous in this
country, and all yet discovered appear to have belonged to
modern types. The Eocene species described are mostly wading
birds, but here, and in the later Tertiary deposits, some charac-
teristic American forms make their appearance, strongly fore-

20

shadowing our present avian fauna. The extinct genera are the
Eocene Uintornis, related to the Woodpeckers, and Aletorms,
which includes several species of Waders./ Among the existing
genera found in our Tertiary beds are, Aquila, Bubo, Meleagris,
Grus, Graculus, Puffinus, and Catarractes. The Great Auk
(Alca impennis), which was once very abundant on our North-
east Coast, has become extinct within a few years.

In this brief summary of the past life of Reptiles and Birds
in America, I have endeavored to exclude doubtful forms, and
those very imperfectly known, preferring to present the conclu-
sions reached by careful study, incomplete though they be, rather
than weary you with a descriptive catalogue of all the fossils
to which names have been applied. VEven this condensed
review can hardly fail to give you some conception of the
wealth of our continent in the extinct forms of these groups,
and thus to suggest what its actual life must have been. J

Although the Trias offers at present the first unquestioned
evidence of true Reptiles, we certainly should not be justified
in supposing for a moment that older forms did not exist. So
too in considering the different groups of Reptiles, which seem
to make their first appearance at certain horizons, flourish for
a time, and then decline, or disappear, every day brings evidence
to show that they are but fragments of the unraveled strands
which converge in the past to form the mystic cord uniting all
life. If the attempt is made to follow back any single thread,
and thus trace the lineage of a group, we are met by difficulties
which the science of to-day can only partially remove. And yet
the anatomist constantly sees in the fragments which he studies
hints of relationship which are to him sure prophecies of future
discoveries.

vThe genealogy of the Chelonia is at present unknown, and
our American extinct forms, so far as we now have them,
throw little light on their ancestry. This is essentially true,
also, of our Plesiosauria, Laceriilia and Ophidia, although sug-
gestive facts are not wanting to indicate possible lines of
descent. With the Crocodilia, however, the case seems to be

21

different, and Huxley has clearly pointed out the path for
investigation. It is probable that material already exists in
our museums for tracing the group through several important
steps in its development. ( We have already seen that the
modern proccelian type of this order goes back only to the
Upper Cretaceous, while the Belodonts, of our Triassic rocks,
with their biconcave vertebrae, are the oldest known Croco-
dilians. Our Jurassic, unfortunately, throws but little light on
the intermediate forms, but we know that the line was con-
tinued, as it was in the old world through Teleosaurus. The
beds of the Rocky Mountain Wealden have just furnished us
with a genuine "missing link," a saurian (Diplosaurus) with
essentially the skull and teeth of a modern Crocodile, and the
vertebras of its predecessor from the Trias. This peculiar rep-
tile clearly represents an important stage in the progressive
series, and evidently one soon after the separation of the Croc-
odile branch from the main stem, j; The modern Gavial type
appears to have been developed about the same time, as the form
was well established in the Upper Cretaceous genus, Thoraco-
saurus. The Teleosaurian group, with biconcave vertebrae,
evidently the parent stock of Crocodilians, became extinct with
Hyposaurus of the same horizon, leaving the Crocodile and
Gavial, with their more perfect proccelian vertebrae, to contend
for the supremacy.. In the early Eocene, both of these types
wrere abundant, but some of the Crocodiles possessed characters
pointing towards the Alligators, which do not appear to have
been completely differentiated until later.

Nothing is really known to-day of the earlier genealogy of
the Pterosauria, but our American forms, without teeth, are
clearly the last stage in their development before this peculiar
group became extinct. The oldest European form, Dimorphodmi,
from the Lower Lias, had the entire jaws armed with teeth, and
was provided with a long tail. The later genus Pterodactyhis
retained the teeth, but had essentially lost the tail ; while
Ramphorhynchus had retained the elongated tail, but had lost
the teeth from the fore part of both jaws. In the genus Pterano-

22

don from the American Cretaceous, the teeth are entirely absent,
and the tail is a mere rudiment. In the gradual loss of the
teeth and tail, these reptiles followed the same path as Birds, and
might thus seem to approach them, as many have supposed.
This resemblance, however, is only a superficial one, as a study
of the more important characters of the Pterodactyls shows
that they are an aberrant type of Reptiles, totally off the line
through which the Birds were developed. The announcement
made not long since in Europe, and accepted by some American
authors, that the Pterosauria, in consequence of certain points
in their structure, were essentially Birds, is directly disproved
by American specimens, far more perfect than those on which
the conclusion was based,
(it is now generally admitted by biologists who have made
a study of the vertebrates, that Birds have come down to us
through the Dinosaurs, and the close affinity of the latter
with recent Struthious Birds will hardly be questioned. The
case amounts almost to a demonstration, if we compare, with
Dinosaurs, their contemporaries, the Mesozoic Birds. The
classes of Birds and Reptiles, as now living, are separated by a
gulf so profound that a few years since it was cited by the
opponents of evolution as the most important break in the
animal series, and one which that doctrine could not bridge
over. Since then, as Huxley has clearly shown, this gap
has been virtually rilled by the discovery of bird-like Reptiles
and reptilian Birds. Compsognathus and Avchazopteryx of the
Old World, and Ichthyornis and Hesperornis of the New, are
the stepping stones by which the evolutionist of to-day leads
the doubting brother across the shallow remnant of the gulf,
once thought impassable. J,

It remains now to consider the highest group of the Animal
Kingdom, the class Mammalia, which includes Man. Of the
existence of this class before the Trias we have no evidence,
either in this country or in the Old World, and it is a significant
fact that at essentially the same horizon in each hemisphere, sim-

23

ilar low forms of Mammals make their appearance. Although
only a few incomplete specimens have been discovered, they
are characteristic and well preserved, and all are apparently
Marsupials, the lowest Mammalian group which we know in
this country, living or fossil. The American Triassic Mam-
mals are known at present only from two small lower jaws, on
which is based the genus JJromotherium, supposed to be related
to the insect-eating Myrmecobius, now living in Australia.

Although the Jura of Europe has yielded other similar
Mammals, we have as yet none of this class from that forma-
tion ; while, from rocks of Cretaceous age, no Mammals are
known in any part of the world. This is especially to be
regretted, as it is evidentlv to the Cretaceous that we must
look for the first representatives of many of our present groups
of Mammals, as well as for indications of their more ancient
lineage. That some discovery of this nature from the Creta-
ceous is near at hand, I cannot doubt, when I consider what the
last few years have brought to light in the Eocene.

In the lowest Tertiary beds of this country, a rich Mam-
malian fauna suddenly makes its appearance, and from that
time through the Age of Mammals to the present, America
has been constantly occupied by this type of life in the greatest
diversity of form. Fortunately, a nearly continuous record of
this life, as preserved, is now accessible to us, and ensures great
additions to our knowledge of the genealogy of Mammals, and
perhaps the solution of more profound problems. Before pro-
ceeding to discuss in detail American fossil Mammalia, it is
important to define the divisions of time indicated in our
Tertiary and Post-Tertiary deposits, as these in many cases
mark successive stages in the development of the mammals.

The boundary line between the Cretaceous and Tertiary in
the region of the Eocky Mountains has been much in dispute
during the last few years, mainly in consequence of the uncer-
tain geological bearings of the fossil plants found near this hori-
zon. The accompanying invertebrate fossils have thrown little
light on the question, which is essentially, whether the great

24

Lignite series of the West is uppermost Cretaceous, or lowest
Eocene. The evidence of the numerous vertebrate remains is,
in my judgment, decisive, and in favor of the former view.

This brings up an important point in Palaeontology, one to
which my attention was drawn several years since, namely :
the comparative value of different groups of fossils in marking
geological time. In examining the subject with some care, I
found that, for this purpose, plants, as their nature indicates,
are most unsatisfactory witnesses; that invertebrate animals
are much better ; and that vertebrates afford the most reliable
evidence of climatic and other geological changes. The sub-
divisions of the latter group, moreover, and in fact all forms
of animal life, are of value in this respect, mainly according
to the perfection of their organization, or zoological rank.
Fishes, for example, 'are but slightly affected by changes that
would destroy Reptiles or Birds, and the higher Mammals
succumb under influences that the lower forms pass through
in safety. The more special applications of this general law,
and its value in geology, will readily suggest themselves.

The evidence offered by fossil remains is, in the light of this
law, conclusive, that the line, if line there be, separating our
Cretaceous from the Tertiary, must at present be drawn where
the Dinosaurs and other Mesozoic vertebrates disappear, and
are replaced by the Mammals, henceforth the dominant type.
r The Tertiary of Western America comprises the most exten-
sive series of deposits of this age known to geologists, and
important breaks in both the rocks and the fossils separate it
into three well-marked divisions. .These natural divisions are
not the exact equivalents of the Eocene, Miocene, and Pliocene
of Europe, although usually so considered, and known by the
same names ; but, in general, the fauna of each appears to be
older than that of its corresponding representative in the other
hemisphere; an important fact, not hitherto recognized. This
partial resemblance of our extinct faunas to others in regions
widely separated, where the formations are doubtless somewhat
different in geological age, is precisely what we might expect,

25

if, as was probable, the main migrations took place from this
Continent. It is better at once to recognize this principle,
rather than attempt to bring into exact parallelism, formations
that were not strictly contemporaneous.

The freshwater Eocene deposits of our Western Territories,
which are in the same region at least two miles in vertical
thickness, may be separated into three distinct subdivisions.
The lowest of these, resting unconformably on the Cretaceous,
has been termed the Vermilion Creek, or Wahsatch, Group. It
contains a well-marked mammalian fauna, the largest and most
characteristic genus of which is the ungulate Coryphodon, and
hence I have called these deposits the Coryphodon Beds. The
middle Eocene strata, which have been termed the Green
River and Bridger Series, may be designated as the Dinoceras
Beds, as the gigantic animals of this order are only found here.
The uppermost Eocene, or the Uintah Group, is especially
well characterized by large mammals of the genus Diplacodon,
and hence may be termed the Diplacodon Beds. The fauna of
each of these three subdivisions was essentially distinct, and the
fossil remains of each were entombed in different and successive
ancient lakes. It is important to remember that these Eocene
lake-basins all lie between the Rocky Mountains on the east
and the Wahsatch Range on the west, or along the high
central plateau of the Continent. As these mountain chains
were elevated, the enclosed Cretaceous sea, cut off from the
ocean, gradually freshened, and formed these extensive lakes,
while the surrounding land was covered with a luxuriant trop-
ical vegetation, and with many strange forms of animal life.
As the upward movement of this region continued, these lake-
basins, which for ages had been filling up, preserving in their
sediments a faithful record of Eocene life-history, were slowly
drained by the constant deepening of the outflowing rivers, and
they have since remained essentially dry land.

The Miocene lake-basins are on the flanks of this region,
where only land had been since the close of the Cretaceous.
These basins contain three faunas, nearly or quite distinct. The

4

26

lowest Miocene, which is only found east of the Eocky Moun-
tains, alone contains the peculiar mammals known as the Bran-
totheridce, and these deposits may be called the Brontotherium
Beds. The strata next above, which represent the middle Mio-
cene, have as their most characteristic fossil the genus Oreodon,
and are known as the Oreodon Beds. The upper Miocene, which
occurs in Oregon, is of great thickness, and from one of its most
important fossils, Mwhippus, may be designated as the Miohip-
pus Series. The climate here during this period was warm
temperate.

Above the Miocene, east of the Eocky Mountains and on the
Pacific Coast, the Pliocene is well developed, and is rich in
vertebrate remains. The strata rest unconformably on the
Miocene, and there is a well marked faunal change at this
point, modern types now first making their appearance. For
these reasons, we are justified in separating the Miocene from
the Pliocene at this break ; although in Europe where no
marked break exists, the line seems to have been drawn at a
somewhat higher horizon. Our Pliocene forms essentially a
continuous series, although the upper beds may be distin-
guished from the lower by the presence of a true Equus, and
some other existing genera.,- The Pliocene climate was similar to
that of the Miocene. The Post-Pliocene beds contain many ex-
tinct mammals, and may thus be separated from recent deposits.

Eeturning now to our subject from this geological digression,
— which will hardly be deemed unprofitable, since I have given
you in few words the results of a great deal of hard mountain
work, — let us consider the Tertiary mammals, as we know
them from the remains already discovered, and attempt to
trace the history of each order down to the present time. We
have seen that a single small Marsupial, from the Trias, is
the only mammal found in all the American rocks below the
Eocene ; and yet in beds of this age, immediately over the
Chalk, fossil mammals of many different kinds abound.

The Marsupials, strange to say, are here few in number, and
diminutive in size; and have as yet been identified only by frag-

27

mentary specimens, and most of them too imperfect for accurate
description. In the higher Eocene deposits, this group is more
abundant, but still represented by small animals, most of them
insectivorous, or carnivorous in habit, like the existing Opos-
sum. From the Miocene and Pliocene, no remains of Marsupials
have been described. From the Post-Tertiary, only specimens
nearly allied to those now living are known, and most of these
were found in the caves of South America.

The Edentate Mammals are evidently an American type,
and on this Continent attained a great development in numbers
and size. No Eocene Edentates have been found here, and
although their discovery in this formation has been announced,
the identification proves to have been erroneous. In the Mio-
cene of the Pacific Coast, a few fossils have been discovered
which belong to animals of this group, and to the genus Moropus.
There are two species, one about as large as a Tapir, and the
other nearly twice that size. This genus is the type of a dis-
tinct family, the Moropodidce. In the lower Pliocene above,
well preserved remains of Edentates of very large size have
been found at several widely separated localities in Idaho and
California. These belong to the genus Morotherium, of which
two species are known. East of the Eocky Mountains, in the
lower Pliocene of Nebraska, a large species apparently of the
genus Moropus has been discovered. The horizon of these
later fossils corresponds nearly with beds in Europe that have
been called Miocene. In the Post-Pliocene of North America,
gigantic Edentates were very numerous and widely distributed,
but all disappeared with the close of that period.") These forms
were essentially huge Sloths, and the more important genera
were Megatherium, Mylodon and Megalonyx. The genera
Megalocnus and Myomorphus have been found only in Cuba,

In South America during the Pliocene or Post-Pliocene,
enormous Edentates were still more abundant, and their
remains are usually in such perfect preservation as to suggest
a very recent period for their extinction. The Sloth tribe
is represented by the huge Mylodon, Megatherium, Megalonyx,

28

Coelodon, Ochotherium, Gnathopis, Lestodon, Scelidotherium, and
Sphcenodon ; and among the Armadilloes were Chlamydotherium,
Eurydon, Glyp>todon, Heterodon, Pachytlterium and Scliistopleurum.
Glossotheriwn, another extinct genus, is supposed to be allied
to the Ant-eaters.

It is frequently asserted, and very generally believed, that the
large number of huge Edentata which lived in North America
during the Post-Pliocene, were the results of an extensive
migration from South America soon after the elevation of
the Isthmus of Panama, near the close of the Tertiary. No
conclusive proof of such migration has been offered, and
the evidence, it seems to me, so far as we now have it, is
directly opposed to this view. No undoubted Tertiary Edentates
have yet been discovered in South America, while we have at
least two species in our Miocene, and during the deposition of
our lower Pliocene, large individuals of this group were not
uncommon as far north as the forty-third parallel of latitude,
on both sides of the Rocky Mountains. In view of these facts,
and others which I shall lay before you, it seems more natural
to conclude from our present knowledge, that the migration,
which no doubt took place, was from north to south. The
Edentates finding thus in South America a congenial home
flourished greatly for a time, and although the larger forms are
now all extinct, diminutive representatives of the group still
inhabit the same region.

The Cetacea first appear in the Eocene, as in Europe, and
are comparatively abundant in deposits of this age on the
Atlantic Coast. The most interesting remains of this order, yet
found, belong to the Zeuglodontidce, which are carnivorous
whales, and the only animals of the order with teeth implanted
by twro roots. The principal genera of this family are Zeughdon
and Squalodon, the former genus being represented by gigantic
forms, some of which were seventy feet in length. The genus
Saurocetes, which includes some small animals of this group, has
been found in South America. The Dolphin family (Delphini-
dce) are well represented in the Miocene, both on the Atlantic

29

and Pacific Coast. The best known genus is Priscodelphmus, of
which several species have been described. Several other
generic names which have been applied to fragments need not
here be enumerated. In none of the Tertiary species of this
family were the cervical vertebras ankylosed. The Sperm
Whales (Catodontidce) were also abundant throughout the Ter-
tiary, and with them in the earlier beds, various Ziphioid forms
have been found. The toothless Balaenidae are only known
with certainty as fossils from the later Tertiary and more
recent deposits.

The Sirenians, which appear first in the Eocene of the
Old World, occur in the Miocene of our Eastern Coast, and
throughout the later Tertiary. The specimens described have
all been referred to the genus Manatus, and seem closely
related to our living species. In the Tertiary of Jamaica, a
skull has been found which indicates a new genus, Prorastomus,
also allied to the existing Manatee. The genus Rhytina, once
abundant on our Northwest Coast, has recently become extinct.

The Ungulates are the most abundant Mammals in the Ter-
tiary, and the most important; since they include a great
variety of types, some of which we can trace through their
various changes down to the modified forms that represent
them to-day. Of the various divisions in this comprehensive
group, the Perissodactyle, or odd-toed Ungulates, are evidently
the oldest, and throughout the Eocene are the prevailing forms.
Although all of the Perissodactyles of the earlier Tertiary are
more or less generalized, they are still quite distinct from the
Artiodaetyles, even at the base of the Eocene. One
family, however, the Coryphodonlidce, which is well represented
at this horizon, both in America and Europe, although essen-
tially Perissodactyle, possesses some characters which point to a
primitive Ungulate type from which the present orders have
been evolved. Among these characters are the diminutive
brain, which in size and form approaches that of the Reptiles,
and also the five-toed feet from which all the various forms of
the mammalian foot have been derived. Of this family, only

30

a single genus, Coryphodon (Bathmodon), is known, but there
were several distinct species. They were the largest mammals
of the lower Eocene, some exceeding in size the existing Tapirs.

In the middle Eocene, West of the Rocky Mountains, a
remarkable group of ungulates makes its appearance. These
animals nearly equaled the Elephant in size, but had shorter
limbs. The skull was armed with two or three pairs of horn-
cores, and with enormous canine tusks. The brain was propor-
tionally smaller than in any other land mammal. The feet had
five toes, and resembled in their general structure those of Co-
ryphodon, thus indicating some affinity with that genus. These
mammals resemble in some respects the Perissodactyles, and in
others the Proboscidians, yet differ so widely from any known
Ungulates, recent or fossil, that they must be regarded as form-
ing a distinct order, the Dinocerata. Only three genera are
known, Dinoceras, Tinoceras and Uinta theriiim, but quite a num-
ber of species have been described. During the later part of the
middle Eocene, these animals were very abundant for a short
time, and then became extinct, leaving apparently no succes-
sors, unless possibly we have in the Proboscidians their much
modified descendants./ Their genetic connection with the
Coryphodonts is much more probable, in view of what we
now know of the two groups.

Besides these peculiar Mammals, which are extinct, and
mainly of interest to the Biologist, there were others in the
early Tertiary which remind ns of those at present living
around us. When a student in Germany some twelve years
ago, I heard a world-renowned Professor of Zoology gravely
inform his pupils that the Horse was a gift of the Old World
to the New, and was entirely unknown in America until
introduced by the Spaniards. After the lecture, I asked him
whether no earlier remains of horses had been found on
this Continent, and was told in reply that the reports to that
effect were too unsatisfactory to be presented as facts in science.
This remark led me, on my return, to examine the subject
myself, and I have since unearthed, with my own hands, not less

31

than thirty distinct^ species of the horse tribe, in the Tertiary
deposits of the West alone ; and it is now, I think generally
admitted that America is, after all, the true home of the Horse.

I can offer you no better illustration than this of the advance
vertebrate palaeontology has made during the last decade, or of
the important contributions to this progress which our Kocky
Mountain region has supplied.

The oldest representative of the horse, at present known, is
the diminutive Eohippus from the lower Eocene. Several spe-
cies have been found, all about the size of a fox. Like most
of the early mammals, these Ungulates had forty-four teeth,
the molars with short crOwns, and quite distinct in form from
the premolars. The ulna and the fibula were entire and dis-
tinct, and there were four well developed toes and a rudiment
of another on the fore feet, and three toes behind. In the
structure of the feet, and in the teeth, the Eohippus indicates
unmistakably that the direct ancestral line to the modern horse
has already separated from the other Perissodactyles. In the
next higher division of the Eocene, another genus (Orohippus)
makes its appearance, replacing Eohippus, and showing a
greater, although still distant, resemblance to the Equine type.
The rudimentary first digit of the fore foot has disappeared,
and the last premolar has gone over to the molar series. Oro-
hippus was but little larger than Eohippus, and in most other
respects very similar. Several species have been found in the
same horizon with Di?ioceras, and others lived during the upper
Eocene with Diplacodon, but none later.

Near the base of the Miocene, in the Brontotherium beds,
we find a third closely allied genus, Mesohippus, which is about
as large as a sheep, and one stage nearer the horse. There are
only three toes and a rudimentary splint bone on the fore feet,
and three toes behind. Two of the premolar teeth are quite
like the molars. The ulna is no longer distinct, or the fibula
entire, and other characters show clearly that the transition is
advancing. In the upper Miocene, Mesohippus is not found,
but in its place a fourth form, Miohippus, continues the line.

32

This genus is near the Anchitherium of Eiyope, but presents
several important differences. The three toes in each foot are
more nearly of a size, and a rudiment of the fifth metacarpal
bone is retained. All the known species of tins genus are larger
than those of Mesohippus, and none pass above the Miocene.

The genus Protohippus of the lower Pliocene, is yet more
equine, and some of its species equaled the ass in size. There
are still three toes on each foot, but only the middle one, cor-
responding to the single toe of the horse, comes to the ground.
This genus resembles most nearly the Hipparion of Europe.
In the Pliocene, we have the last stage of the series before
reaching the horse, in the genus Pliohippus, which has lost the
small hooflets, and in other respects is very equine. Only in
the upper Pliocene, does the true Equus appear, and complete
the genealogy of the Horse, which in the Post-Tertiary roamed
over the whole of North and South America, and soon after
became extinct. This occurred long before the discovery of
the Continent by Europeans, and no satisfactory reason for the
extinction has yet been given. Besides the characters I have
mentioned, there are many others, in the skeleton, skull, teeth,
and brain of the forty or more intermediate species, which
show that the transition from the Eocene Eohippus to the
modern Equus, has taken place in the order indicated, and I
believe the specimens now at New Haven will demonstrate
the fact to any anatomist. They certainly carried prompt
conviction to the first of anatomists, who was the honored guest
of the Association a year ago, whose genius had alreadjr indi-
cated the later genealogy of the horse in Europe, and whose
own researches so well qualified him to appreciate the evidence
here laid before him. Did time permit, I might give you at
least a probable explanation of this marvellous change, but
justice to the comrades of the horse in his long struggle for
existence demands that some notice of their efforts should be
placed on record.

Beside the Horse and his congeners, the only existing Peris-
sodactyles are the Rhinoceros and the Tapir. The last is the

33

oldest type, but the Rhinoceros had near allies throughout the
Tertiary ; and, in view of the continuity of the equine line, it is
well worth while to attempt to trace his pedigree. At the
bottom of the Eocene, in our Western lake-basins, the tapiroid
genus Helaletes is found, represented by numerous small mam-
mals hardly larger than the diminutive horses of that day. In
the following epoch of the Eocene, the closely allied Hyrachyus
was one of the most abundant animals. This genus was nearly
related to the Lopltiodon of Europe, and in its teeth and skele-
ton strongly resembled the living Tapir ; whose ancestry, to
this point, seems to coincide with that of the Rhinoceros we
are considering. Strangely enough, the Rhinoceros line, before
it becomes distinct, separates into two branches. In the upper
part of the Dinoceras Beds, we have the genus Colonoceras,
which is really a Hyrachyus with a transverse pair of very
rudimentary horn-cores on the nasal bones. In the lower
Miocene west of the Rocky Mountains, this line seems to pass
on through the genus Dicer atherium, and in the higher Miocene
this genus is well represented. Some of the species nearly
equaled in size the existing Rhinoceros, which Dicer atherium
strongly resembled. The main difference between them is a
most interesting one. The rudimentary horn-cores on the
nasals, seen in Colonoceras, are in Dicer atherium developed into
strong bony supports for horns, which were placed transversely,
as in the Ruminants, and not on the median line, as in all
existing forms of Rhinoceros. In the Pliocene of the Pacific
Coast, a large Rhinoceros has been discovered, which may
be a descendant of Dicer atherium, but as the nasal bones have
not been found, we must wait for further evidence on this
point. Returning now to the other branch of the Rhinoceros
group, which left their remains mainly East of the Rocky
Mountains, we find that all the known forms are hornless.
The upper Eocene genus Amynodon is the oldest known
Rhinoceros, and by far the most generalized of the family.
The premolars are all unlike the molars, the four canines are
of large size, but the inner incisor in each jaw is lost in the

5

34

fully adult animal. The nasals were without horns. There
were four toes in front, and three behind. The genus Hyrac-
odon, of the Miocene, which is essentially a Rhinoceros, has
a full set of incisor and canine teeth; and the molars are so
nearly like those of its predecessor Hyrachyus, that no one will
question the transformation of the older into the newer type.
Hyracodon, however, appears to be off the true line, for it has
but three toes in front. In the higher Miocene beds, and
possibly with Hyracodon, occurs a larger Rhinoceros, which
has been referred to the genus Aceratherium. This form has
lost the canine and one incisor above, and two incisors below.
In the Pliocene are several species closely related, and of large
size. Above the Pliocene in America, no vestiges of the
Rhinoceros have been found, and our American forms doubt-
less became extinct at the close of this period.

The Tapir is clearly an old American type, and we have
seen that, in the Eocene, the genera Helaletes and Hyrachyus
were so strongly tapiroid in their principal characters, that the
main line of descent probably passed through them. It is
remarkable that the Miocene of the West, so greatly developed as
it is on both sides of the Rocky Mountains, should have yielded
but a few fragments of tapiroid mammals, and the same is true
of the Pliocene of that region. In the Miocene of the Atlantic
Coast, too. only a few imperfect specimens have been found.
These forms all apparently belong to the genus Tapiravus,
although most of them have been referred to Lophiodon, a lower
Eocene type. _, In the Post-Tertiary, a true Tapirus was abun-
dant, and its remains have been found in various parts of North
America. The line of descent, although indistinct through
the middle and upper Tertiary, was doubtless continuous in
America, and several species exist at present, from Mexico
southward. It is worthy of notice that the species North of
the Isthmus of Panama appear all to be generically distinct
from those of South America.

In addition to these three Perissodactyle types which, as
the fittest, have alone survived, and whose lineage I have

35

endeavored to trace, there were many others in early Tertiary
times. Some of these disappeared with the close of the
Eocene, while others continued, and assumed strange special-
ized shapes in the Miocene, before their decline and extinction.
One series of the latter deserves especial mention, as it includes
one of the most interesting families of our extinct animals.
Among the large mammals in the lower Eocene is Limnohyus,
a true Perissodactyle, but only known here from fragments of
the skeleton. In the next higher beds, this genus is well
represented, and with it is found a nearly allied form, Palceo-
syops. In the upper Eocene, both have left the field, and the
genus Dtplacodon, a very near relative, holds the supremacy.
The line seems clear through these three genera, but on
crossing the break into the Miocene, we have, apparently as
next of kin, the huge Brontotheridce. These strange beasts show
in their dentition and some other characters the same transition
steps beyond Diplaeodon, which that genus had made beyond
Palceosyops. The Brontotheridce were nearly as large as the
Elephant, but had much shorter limbs. The skull was elon-
gated, and had a transverse pair of large horn-cores on the
maxillaries, in front of the orbits, like the middle pair in
Dinoceras. There were four toes in front, and three behind,
and the feet were similar to those of the Ehinoceros. There
are four genera in this group, Brontotherium ; Dieonodon; Meno-
dus (TitanotJieriwn) ; and Megacerops, which have been found
only in the lowest Miocene, east of the Rocky Mountains.

In the higher Miocene beds of Oregon, an allied genus,
Chalicotherium, makes its appearance. It is one stage further
on in the transition, and perhaps a descendant of the Bronto-
theridce ; but here, so far as now known, the line disappears.
It is a suggestive fact, that this genus has now been found in
Western America, China, India, Greece, Germany and France,
indicating thus, as I believe, the path by which many of our
ancient mammals helped to people the so-called Old World.

The Artiodactyles, or even-toed Ungulates, are the most
abundant of the larger mammals now living; and the group

36

dates back at least to the lowest Eocene. Of the two well
marked divisions of this order, the Bunodonts and the Seleno-
donts, as happily defined by Kowalevsky, the former is the
older type, which must have separated from the Perissodactyle
line after the latter had become differentiated from the prim-
itive Ungulate. In the Coryphodon Beds of New Mexico,
occurs the oldest Artiodactyle yet found, but it is at present
known only from fragmentary specimens. These remains are
clearly Suilline in character, and belong to the genus Eohyus.
In the beds above, and possibly even in the same horizon,
the genus Helohyus is not uncommon, and several species are
known. The molar teeth of this genus are verv similar to
those of the Eocene Hyracotlierium, of Europe, which is sup-
posed to be a Perissodactyle, while Helohyus certainly is not,
but apparently a true lineal ancestor of the existing pigs.
In every vigorous primitive type which was destined to survive
many geological changes, there seems to have been a tendency
to throw off lateral branches, which became highly specialized
and soon died out, because they are unable to adapt themselves
to new conditions. The narrow path of the persistent Suilline
type, throughout the whole Tertiary, is strown with the remains
of such ambitious offshoots, while the typical pig, with an
obstinacy never lost, has held on in spite of Catastrophes and
Evolution, and still lives in America to-day. In the lower
Eocene, we have in the genus Parahyus apparently one of these
short-lived, specialized branches. It attained a much larger
size than the true lineal forms, and the number of its teeth
was reduced. In the Dinoceras Beds, or middle Eocene, we
have still, on or near the true line, Helohyus, which is the
last of the series known from the American Eocene. All
these early Suillines, with the possible exception of Parahyus,
appear to have had at least four toes, all of usable size.

In the lower Miocene, we find the genus Perchcerus, seem-
ingly a true Suilline, and with it remains of a larger form,
Elotherium, are abundant. The latter genus occurs in Europe
in nearly the same horizon, and the specimens known from

37

each Continent agree closely in general characters. The name
Pelonax has been applied erroneously to some of the American
forms ; but the specimens on which it was based clearly belong
to Elotherium. This genus affords another example of the
aberrant Suilline offshoots, already mentioned. Some of the
species were nearly as large as a Rhinoceros, and in all there were
but two serviceable toes; the outer digits, seen in living ani-
mals of this group, being represented only by small rudiments
concealed beneath the skin. In the upper Miocene of Oregon,
Suillines are abundant, and almost all belong to the genus
Thinohyus, a near ally of the modern Peccary (Dicotyles), but
having a greater number of teeth, and a few other distinguish-
ing features. In the Pliocene, Suillines are still numerous, and
all the American forms yet discovered are closely related to
Dicotyles. The genus Platygonus is represented by several
species, one of which was very abundant in the Post-Tertiary
of North America, and is apparently the last example of a side
branch, before the American Suillines culminate in existing
Peccaries. The feet in this species are more specialized than
in the living forms, and approach some of the peculiar features
of the ruminants; as for example a strong tendency to coales-
cence in the metapodial bones. The genus Platygonus became
extinct in the Post-Tertiary, and the later and existing species
are all true Peccaries. No authenticated remains of the genera
Sus, Porous, Phacochoerus, or the allied Hi.pjjojjolamus, the Old
World Suillines, have been found in America, although several
announcements to that effect have been made.

In the series of generic forms between the lower Eocene
Eoliyus and the existing Dicotyles. which I have very briefly
discussed, we have apparently the ancestral line ending in the
typical American Suillines. Although the demonstration is
not yet as complete as in the lineage of the Horse, this is not
owing to want of material, but rather to the fact that the
actual changes which transformed the early Tertiary pig into
the modern Peccary were comparatively slight, so far as they
are indicated in the skeletons preserved, while the lateral

38

branches were so numerous as to confuse the line. It is clear,
however, that from the close of the Cretaceous to the Post-
Tertiary, the Bunodont Artiodactyles were especially abun-
dant on this Continent, and only recently have approached
extinction.

The Selenodont division of the Artiodactyles is a more
interesting group and, so far as we now know, makes its first
appearance in the upper Eocene of the West, although forms,
apparently transitional, between it and the Bunodonts occur in
the Dinoceras Beds, or middle Eocene. These belong to the
genus Homacodon, which is very nearly allied to Helohyus and
but a single step away from this genus toward the Selenodonts.
By a fortunate discovery, a nearly complete skeleton of this
rare intermediate form has been brought to light, and we are
thus enabled to define its characters. Several species of
Homacodon are known, all of small size. This primitive
Selenodont had forty-four teeth, which formed a nearly con-
tinuous series.

The molar teeth are very similar to those of Helohyus, but
the cones on the crowns have become partially triangular in
outline, so that when worn, the Selenodont pattern is clearly
recognizable. The first and second upper molars, moreover,
have three distinct posterior cusps, and two in front; a peculiar
feature, which is seen also in the European genera Dichobune
and Cainotherium. There were four toes on each foot, and the
metapodial bones were distinct. The type species of this genus
was about as large as a cat. With Helohyus, this genus forms
a well marked family, the Helokyidoe.

In the Diplacodon horizon of the upper Eocene, the Seleno-
dont dentition is no longer doubtful, as it is seen in most of
the Artiodactyla yet found in these beds. These animals are
all small, and belong to at least three distinct genera. One of
these, Eomeryx, closely resembles Homacodon in most of its
skeleton, and has four toes, but its teeth show well marked
crescents, and a partial transition to the teeth of Hyopolamus,
from the Eocene of Europe. With this genus, is another

39

(Parameryx), also closely allied to Homacodon, but apparently a
straggler from the true line, as it has but three toes behind.
The most pronounced Selenodont in the upper Eocene is the
Oromeryx, which genus appears to be allied to the existing
Deer family, or Cervidce, and if so is the oldest known repre-
sentative of the group. These facts are important, as it has
been supposed, until very recently, that our Eocene contained
no even-hoofed mammals.

In the lowest Miocene of the West, no true crescent-toothed
Artiodactyla have as yet been identified, with the exception
of a single species of Hyopolamus ; but in the overlying beds
of the middle Miocene, remains of the Oreodonlidue occur in
such vast numbers as to indicate that these animals must
have lived in large herds around the borders of the lake-basins
in which their remains have been entombed. These basins are
now the denuded deserts so well termed Mauvaises Terres by
the early French trappers. The least specialized, and apparently
the oldest, genus of this group is Agriochoerus, which so nearly
resembles the older Hyopotamus, and the still more ancient
Eomeryx, that we can hardly doubt that they all belonged to
the same ancestral line. The typical Oreodonts are the genera
Oreodon and Eporeodon, which have been aptly termed by
Leidy, ruminating hogs. They had forty-four teeth, and four
well developed toes on each foot. The true Oreodons, which
were most numerous east of the Rocky Mountains, were about
as large as the existing Peccary, while Eporeodon, which was
nearly twice this size, was very abundant in the Miocene of
the Pacific slope.

In the succeeding Pliocene formation, on each side of the
Rocky Mountains, the genus Meryckyus is one of the prevailing-
forms, and continues the line on from the Miocene, where the
true Oreodons became extinct. Beyond this, we have the genus
Merychoclmrus, which is so nearly allied to the last, that tbey
would be united bv many naturalists. With the close of the
Pliocene, this series of peculiar ruminants abruptly terminates,
no member surviving until the Post-Tertiary, so far as known.

40

A most interesting line, that leading to the Camels and Lla-
mas, separates from the primitive Selenodont branch in the
Eocene, probably through the genus Parameryx. In the Mio-
cene, we find in Poebrotherium and some nearly allied forms
unmistakable indications that the Cameloid type of ruminant
had already become partially specialized, although there is a
complete series of incisor teeth, and the metapodial bones are
distinct. In the Pliocene, the Camel tribe was, next to the
Horses, the most abundant of the larger mammals. The line is
continued through the genus Procamelus, and perhaps others,
and in this formation the incisors first begin to diminish, and
the metapodials to unite. In the Post-Tertiary we have a true
Auchenia, represented by several species, and others in South
America, where the Alpacas and Llamas still survive. From
the Eocene almost to the present time, North America has been
the home of vast numbers of the Camelidce, and there can be
little doubt that they originated here, and migrated to the Old
World.

Returning once more to the upper Eocene, we find another
line of descent starting from Oromeryx, which, as we have
seen, had apparently then just become differentiated from the
older Bunodont type. Throughout the middle and upper
Miocene, this line is carried forward by the genus Leptomeryx
and its near allies, which resemble so strongly the Pliocene
Cervidce that they may fairly be regarded as their probable
progenitors. Possibly some of these forms may be related to
the Tragulidce, but at present the evidence is against it.

The Deer family has representatives in the upper Miocene of
Europe, which contains fossils strongly resembling the fauna of
our lower Pliocene, a fact always to be borne in mind in com-
paring the horizon of any group in the two continents. Several
species of Cervidce, belonging to the genus Cosoryx, are known
from the lower Pliocene of the West, and all have very small
antlers, divided into a single pair of tynes. The statement
recently published, that most of these antlers had been broken
during the life of the animals, is unsupported by any evidence,

41

and is erroneous. These primitive Deer do not have the orbit
closed behind, and they have all the four metapodial bones
entire, although the second and fifth are very slender. In the
upper Pliocene, a true Cervus of large size has been discovered.
In the Post-Tertiary, Cervus, Alces, and Tarandus have been met
with, the latter far south of its present range. In the caves of
South America, remains of Cervus have been found, and also two
species of Antelopes, one referred to a new genus, Leptotherium.

The Hollow-horned Ruminants, in this country, appear to
date back no further than to the lower Pliocene, and here only
two species of Bison have as yet been discovered. In the Post-
Tertiary this genus was represented by numerous individuals
and several species, some of large size. The Musk Ox (Ovibos)
was not uncommon during some parts of this epoch, and
its remains are widely distributed.

No authentic fossil remains of true Sheep, Goats, or Giraffes
have as yet been found on this continent.

The Proboscideans, which are now separated from the typi-
cal Ungulates as a distinct order, make their first appearance in
North America in the lower Pliocene, where several species of
Mastodon have been found. This genus occurs, also, in the
upper Pliocene, and in the Post-Tertiary ; although some of
the remains attributed to the latter are undoubtedly older.
The Pliocene species all have a band of enamel on the tusks,
and some other peculiarities observed in the oldest Mastodons
of Europe, which are from essentially the same horizon. Two
species of this genus have been found in South America, in
connection with the remains of extinct Llamas and Horses.
The genus Elephas is a later form, and has not yet been iden-
tified in this country below the upper Pliocene, where one
gigantic species was abundant. In the Post-Pliocene, remains
of this genus are numerous. The hairy Mammoth of the Old
World (Elephas primigenius) was once abundant in Alaska, aud
great numbers of its bones are now preserved in the frozen
cliffs of that region. This species does not appear to have
extended east of the Rocky Mountains, or south of the Colum-

6

42

bia River, but was replaced there by the American Elephant,
which preferred a milder climate. Remains of the latter have
been met with in Canada, throughout the United States, and in
Mexico. The last of the American Mastodons and Elephants
became extinct in the Post-Tertiary.

The order Toxodontia includes two very peculiar genera,
Toxodon and Nesodon, which have been found in the Post-Ter-
tiary deposits of South America. These animals were of huge
size, and possessed such mixed characters that their affinities
are a matter of considerable doubt. They are thought to be
related to the Ungulates, Rodents, and Edentates, but as the
feet are unknown, this cannot at present be decided.

Macrauchenia and Homalodoniotherium are two other peculiar
genera from South America, now extinct, the exact affinities
of which are uncertain. Anoplotherium and Palceolheriwn, so
abundant in Europe, have not been found in our North
American Tertiary deposits, although reported from South
America.

Perhaps the most remarkable mammals yet found in Amer-
ica are the Tittodoniia, which are comparatively abundant in
the lower and middle Eocene. These animals seem to com-
bine the characters of several different groups, viz : the Car-
nivores, Ungulates, and Rodents. In the genus Tillotherium.,
the type of the order, and of the family Tillotheridce, the skull
resembles that of the Bears ; the molar teeth are of the
ungulate type; while the large incisors are very similar to those
of Rodents. The skeleton resembles that of the Carnivores,
but the scaphoid and lunar bones are distinct, and there is a
third trochanter on the femur. The feet are plantigrade, and
each had five digits, all with long pointed claws. In the
allied genus Stylinodon, which belongs to a distinct family, the
Stylinodontidce, all the teeth were rootless. Some of these
animals were as large as a Tapir. The genus Dryplodon has
been found only in the Coryphodon beds of New Mexico, while
Tillotherium and Stylinodon occur in the middle Eocene of
Wyoming. Ancln'ppodus probably belongs to this group, which

43

may perhaps include some other forms that have been named
from fragmentary specimens.

The Rodents are an ancient type, and their remains are not
unfrequently disinterred in the strata of our lowest fresh-water
Eocene. The earliest known forms are apparently all related
to the Squirrels, and the most common genus is Sciuravus,
which continued throughout the Eocene. A nearly allied form,
which may prove to be the same, is Paramys, the species of
which are larger than those of the older type. In the Dino-
ceras beds, the genus Colonomys is found, and the specimens
preserved point to the Muridce, as the nearest living allies. A
peculiar genus, Apatemys, which also occurs in the middle
Eocene, has gliriform incisors, but the molars resemble those of
Insectivores. All the Eocene Rodents are of small size, the
largest being about as large as a rabbit.

In the middle and upper Miocene lake-basins of the West,
Rodents abound, but all are of moderate size. The Hares first
appear in the Oreodon beds, and continue in considerable num-
bers through the rest of the Tertiary and Post-Tertiary to the
present day. In these beds, the most common forms belong to
the Leporidce, and mainly to the genus Palacolagus. The Squirrel
family is represented by Ischyromys, the Muridce by the genus
Mimys, and the Beavers by Palceocastor. In the upper Miocene
of Oregon, most of the same genera are found, and with them
some peculiar forms, very unlike anything now living. One of
these is the genus Allomys, possibly related to the flying
Squirrels, but having molar teeth somewhat like those of the
Ungulates. In the Pliocene, east and west of the Rocky Moun-
tains, Rodents continue abundant, but most of them belong to
existing genera. Among these are Castor, Hystrix, Cynomys,
Geomys, Lepus and Besperomys. In the Post-Tertiary, the
gigantic beaver, Castoroides, was abundant throughout most of
North America. Hydrochoerus has been found in South Caro-
lina. In the caves of the island of Anguilla, in the West
Indies, remains of large extinct Rodents belonging to the Gliin-
cJiillidce have been discovered.

44

The early Tertiary Eodents known from South Ameriea are
the genera Megamys, Theridromys, and a large species referred
to Arvicola. In Brazil, the Pliocene Rodents found are referred
to the existing genera Cavia, Kerodon, Lagostomus, Ctenomys,
Hesperomys, Oxymycterus, Arvicola and Lepus. A new genus,
Cardiodus, described from this horizon, is a true Rodent, but
the peculiar Typolhervum, which has been referred to this order
by some authorities, has perhaps other affinities. In the
Post-Tertiary, the Rodents were very abundant in South
America, as they are at present. The species are in most
instances distinct from those now living, but the genera are
nearly the same. The Caviidae were especially numerous.
Cercolabes, Myopolamus, and Lagostomus are also found, and two
extinct genera, Phyllomys and Lonchophorus.

The Cheiroptera, or Bats, have not been found in this country
below the middle Eocene, where two extinct genera, Nyctilestes
and Nyctitherium, are each represented by numerous remains.
These fossils all belong to small animals, and, so far as they
have been investigated, show no characters of more than generic
importance to distinguish them from the Bats of to-day. No
other members of this group are known from our Tertiary.
In the Post-Tertiary, no extinct species of Bats have been
found in North America, but from the caves of Brazil quite
a number have been reported. These all belong to genera
still living in South America, and most of them to the family
Phyllostomidce.

The Insectivores date back, in this country, at least to the
middle Eocene. Here numerous remains occur, which have
been described as belonging to this order, although it is pos-
sible that some of them were insect-eating Marsupials. The
best known genera are, Hemiacodon, Cerdetodon, Talpavus, and
Entomacodon ; all represented by animals of small size. In
the Miocene, the bones of Insectivores are comparatively abun-
dant, and the genera best determined are Ictops and Leptictis.
A few specimens only have been found in the Pliocene and
Post-Pliocene, most of them related to the Moles. No extinct

45

Insectivores are known from South America, and no member
of the group exists there at present.

The Carnivora, or true flesh-eating animals, are an old type,
well represented in the Eocene, and, as might be expected,
these early forms are much less specialized than the living
species. In the Coryphoclon beds, the genus Limnocyon,
allied to the Pterodon of the European Eocene, is abundant.
Another genus, apparently distinct, is Prolotomus, and several
others have been named from fragmentary fossils. In the
middle Eocene, Carnivores were still more numerous, and many
genera have been discovered. One of these, Limnofelis, was
nearly as large as a lion, and apparently allied to the cats,
although the typical FeKdce seem not yet to have been differen-
tiated. Another Carnivore of nearly equal size was Orocyon,
which had short massive jaws and broad teeth. Dromocyon and
Mesonyx were large animals, allied to Hycenodon. The teeth
were narrow, and the jaws long and slender. Among the
smaller Carnivores were, Vulpavus, Viverravus, Sinopa, Thino-
cyon, and Ziphacodon.

In our Western Miocene, Carnivores are abundant, and
make an approach to modern types. The Felidce are well rep-
resented, the most interesting genus being Afachairodus, which
is not uncommon in the Oreodon beds on both sides of the
Rocky Mountains. An allied genus is Diniclis, and several
smaller Cats are known from about the same horizon. The
Canidce are represented by Amphicyon, a European genus, and
by several species of Canis, or a very nearly allied form. The
peculiar genus Hycenodon, found also in Europe, and the type of
a distinct family, is abundant in the Miocene east of the Rocky
Mountains, but has not yet been found on the Pacific Coast.
In the Pliocene of both regions, the Canidce are numerous,
and all apparently belong to the existing genus Cam's. The
genus Alaclwirodus is still the dominant form of the Cats, which
are abundant, and for the most part belong to the genus Felis.
The extinct Leptarctus is supposed to belong to the Ursidce,
and if so, is the oldest American representative of this family.

46

In the Post-Pliocene, the extinct Felidce include species nearly
as large as a lion, and smaller forms very similar to those still
living. Bears, Eaccoons and Weasels have also been found.

In the Pliocene of South America, Machairodus represents
the Felidte, while the genera Arctotherium and Hycenarctus
belong to the Bear family. Species of J\Justela and Canis have
also been found. In the caves of Brazil, the fauna of which
is regarded as Post-Pliocene, one species of Machairodns is
known, and one of Syncelurus. Ca?iis and Icticyon, still living
in Brazil, and the extinct genus ^eotlios, represent the Canidce.
Mephitis and Gcrficiis, among the Weasels, were also present,
and with them species of Nasua and Arctotherium.

We come now to the highest group of Mammals, the Pri-
mates, which includes the Lemurs, the Apes, and Man. This
order has a great antiquity, and even at the base of the Eocene
we find it represented by several genera belonging to the lower
forms of the group. In considering these interesting fossils, it is
important to have in mind that the Lemurs, which are usually
regarded as Primates, although at the bottom of the scale, are
only found at the present day in Madagascar and the adjacent
regions of the globe. All the American Monkeys, moreover,
belong to one group, much above the Lemurs, while the Old
World Apes are higher still, and most nearly approach Man.

In the lower Eocene of New Mexico, we find a few repre-
sentatives of the earliest known Primates, and among them are
the genera Lemuravus and Limnotherium, each the type of a
distinct family. These genera became very abundant in the
middle Eocene of the West, and with them are found many
others, all however, included in the two families, Lemttravidce
and Lim?iotheridce. Lemuravus appears to have been most
nearly allied to the Lemurs, and is the most generalized form
of the Primates yet discovered. It had forty-four teeth, form-
ing a continuous series above and below. The brain was
nearly smooth, and of moderate size. The skeleton most
resembles that of the Lemurs. A nearly allied genus, belong-
ing to the same family, is Ilyopsodus. Limnotherium (Tomiihe-

47

rium) also is nearly related to the Lemurs, but shows some affin-
ities with the South American Marmosets. This genus had
forty teeth. The brain was nearly smooth, and the cerebellum
large, and placed mainly behind the cerebrum. The orbits are
open behind, and the lachrymal foramen is outside the orbit.
Other genera belonging to the Limnoiheridce are, Notharcios,
Hipposyus, Microsyops, Pahmcodon, Thinolesles and Tehnalolestes.
Besides these, Antiacodon (Anaptomorphus), Bathrodon and Mes-
acodon should probably be placed in the same group. In the
Diplacodon Beds, or Upper Eocene, no remains of Primates have
yet been detected, although they will doubtless be found there.
All the Eocene Primates known from American strata are low
generalized forms, with characters in the teeth, skeleton and
feet that suggest relationships with the Carnivores, and even
with the Ungulates. These resemblances have led palaeontolo-
gists to refer some imperfect specimens to both these orders.

In the Miocene lake basins of the West, only a single spe-
cies of the Primates has been identified with certainty. This
was found in the Oreodon Beds of Nebraska, and belongs to
the genus Laopilhecus, apparently related both to the Liinno-
tlieridce and to some existing South American Monkeys. In
the Pliocene and Post-Pliocene of North America, no remains
of Primates have yet been found.

In the Post-Pliocene deposits of the Brazilian caves, remains
of Monkeys are numerous, and mainly belong to extinct spe-
cies of Callithrix, Cehus and Jacchus, all living South American
genera. Only one extinct genus, Protopithecas, which embraced
animals of large size, has been found in this peculiar fauna.

It is a noteworthy fact, that no traces of any Anthropoid
Apes, or indeed of any Old World Monkeys have yet been
detected in America. Man, however, the highest of the Pri-
mates, has left his bones and his works from the Arctic Circle
to Patagonia. Most of these specimens are clearly Post-Ter-
tiary, although there is considerable evidence pointing to the
existence of Man in our Pliocene. All the remains yet dis-
covered belong to the well-marked genus Homo, and apparently

48

to a single species, at present represented by the American
Indian.

In this rapid review of Mammalian life in America, from its
first known appearance in the Trias down to the present time, I
have endeavored to state briefly the introduction and succes-
sion of the principal forms in each natural group. If time per-
mitted, I might attempt the more difficult task of trying to
indicate what relations these various groups may possibly bear
to each other ; what connection the ancient Mammals of this
continent have with the corresponding forms of the Old World;
and, most important of all, what real progress Mammalian life
has here made since the beginning of the Eocene. As it is, I
can only say in summing up, that the Marsupials are clearly
the remnants of a very ancient fauna, which occupied this
continent millions of years ago, and from which the other
Mammals were doubtless all derived, although the direct evi-
dence of the transformation is wanting.

Although the Marsupials are nearly related to the still
lower Monotremes, now living in the Australian Region, we
have as yet no hint of the path by which these two groups
became separated from the inferior vertebrates. Neither have
we to-day much light as to the genetic connection existing
between Marsupials and the placental Mammalia, although it is
possible that the different orders of the latter had their origin
each from a separate group of the Marsupials.

The presence, however, of undoubted Marsupials in our
lower and middle Eocene, some of them related to the genus
Didelphys, although remotely, is important evidence as to the
introduction of these animals into America. Against this, their
supposed absence in our Miocene and Pliocene can have but
limited weight, when taken in connection with the fact that
they flourished in the Post-Tertiary, and are still abundant.
The evidence we now have is quite as strongly in favor of a
migration of Marsupials from America to the Old World, as the
reverse, which has been supposed by some naturalists. Possi-
bly, as Huxley has suggested, both countries were peopled with
these low mammals from a continent now submerged.

49

The Edentate mammals have long been a puzzle to Zoolo-
gists, and up to the present time no clew to their affinities with
other groups seems to have been detected. A comparison of
the peculiar Eocene Mammals which I have called the Tillo-
dontia, with the least specialized Edentates, brings to light
many curious resemblances in the skull, teeth, skeleton and
feet. These suggest relationship, at least, and possibly we
may yet find here the key to the Edentate genealogy. At
present, the Tillodonts are all from the lower and middle
Eocene, while Moropus, the oldest edentate genus, is found in
the middle Miocene, and one species in the lower Pliocene.

The Edentates have been usually regarded as an American
type, but the few living forms in Africa, and the Tertiary
species in Europe, the oldest known, have made the land
of their nativity uncertain. I have already given you some
reasons for believing that the Edentates had their first home
in North America, and migrated thence to the southern
portion of the continent. This movement could not have
taken place in the Miocene period, as the Isthmus ©f Darien
was then submerged ; but near the close of the Tertiary,
the elevation of this region left a much broader strip of land
than now exists there, and over this, the Edentates and other
mammals made their way, perhaps urged on by the increasing-
cold of the glacial winters. The evidence to-day is strongly in
favor of such a southern migration. This, however, leaves the
Old World Edentates, fossil and recent, unaccounted for; but I
believe the solution of this problem is essentially the same,
namely : a migration from North America. The Miocene rep-
resentatives of this group, which I have recently obtained in
Oregon, are older than any known in Europe, and, strangely
enough., are more like the latter and the existing African types
than like any of our living species. If, now, we bear in mind
that an elevation of only 180 feet would, as Dana has said,
close Behring's Straits, and give a road thirty miles wide from
America to Asia, we can easily see how this migration might
have taken place. That such a Tertiary bridge did exist, we

7

50

have much independent testimony, and the known facts all
point to extensive migrations of animals over it.

The Cetacea are connected with the marine Carnivores through
the genus Zeughdon, as Huxley has shown, and the points of
resemblance are so marked that the affinity cannot be doubted.
That the connection was a direct one, however, is hardly prob-
able, since the diminutive brain, large number of simple teeth,
and reduced limbs in the Whales, all indicate them to be an
old type, which doubtless branched off from the more primi-
tive stock leading to the Carnivores. Our American extinct
Cetaceans, when carefully investigated, promise to throw much
light upon the pedigree of these strange mammals. As most
of the known forms were probably marine, their distribution is
of little service in determining their origin.

That the Sirenians are allied to the Ungulates, is now gen-
erally a'dmitted by anatomists, and the separation of the exist-
ing species in distant localities suggests that they are the rem-
nants of an extensive group, once widely distributed. The
large number of teeth in some forms, the reduced limbs and
other characters, point back to an ancestry near that of the
earliest ungulates. The gradual loss of teeth in the specialized
members of this group, and in the Cetaceans, is quite parallel
with the same change in Edentates, as well as in Pterodactyls
and Birds.

The Ungulates are so distinct from other groups that they
must be one of the oldest natural divisions of mammals, and
they probably originated from some herbivorous marsupial.
Their large size, and great numbers during Tertiary and Post-
tertiary time, render them most valuable in tracing migrations
induced by climate, as well as in showing the changes of
structure which such a contest for existence may produce.

In the review of the extinct Ungulates, I have endeavored
to show that quite a number of genera usually supposed to
belong originally to the Old World are in reality true Amer-
ican types. Among these were the Horse, Rhinoceros, and
Tapir, all the existing odd-toed Ungulates, and besides these

51

the Camel, Pig, and Deer. All these I believe, and many
others, went to Asia from our North West Coast. It must, for
the present, remain an open question whether we may not
fairly elaim the Bovidce, and even the Proboscidea, since both
occur in our strata at about the same horizon as on the other
continent. On this point there is some confusion, at least in
names. The Himalayan deposits called Upper Miocene, and
so rich in Proboscideans, indicate in their entire fauna that
they are more recent than our Niobrara River beds, which, for
apparently good reasons, we regard as Lower Pliocene. The
latter appear to be about the same horizon as the Pikermi
deposits in Greece, also regarded as Miocene. Believing, how-
ever, that we have here a more complete Tertiary series, and a
better standard for comparison of faunas, I have preferred to
retain the names already applied to our divisions, until the
strata of the two continents are more satisfactorily coordinated.

The extinct Rodents, Bats, and Insectivores of America,
although offering many suggestive hints as to their relation-
ship with other groups, and their various migrations, cannot
now be fully discussed. There is little doubt, however, that
the Rodents are a New World type, and, according to present
evidence, they probably had their origin in North America.
The resemblance in so many respects of this order to the
Proboscideans is a striking fact, not yet explained by the im-
perfectly known genealogy of either group.

The Carnivores, too, I must pass by, except to call attention
to a few special forms which accompanied the migrations of
other groups. One of these is Machaii-odus, the saber-toothed
Tiger, which flourished in our Miocene and Pliocene, and
followed the huge Edentates to South America, and the Ungu-
lates across Asia to Europe. With this genus went Hycenodo?i,
and some typical Wolves and Cats, but the Bears came the
other way with the Antelopes. That the Gazelle, Giraffe, Hip-
popotamus, Hyaena and other African types, once abundant in
Asia, did not come, is doubtless because the Miocene bridge
was submerged before they reached it.

52

The Edentates, in their southern migration, were probably
accompanied by the Horse, Tapir and Rhinoceros, although no
remains of the last have yet been found south of Mexico. The
Mastodon, Elephant, Llama, Deer, Peccary, and other mam-
mals, followed the same path. Why the Mastodon, Elephant,
Rhinoceros, and especially the Horse, should have been selected
with the huge Edentates for extinction, and the other Un-
gulates left, is at present a mystery, which their somewhat
larger size hardly explains.

The relations of the American Primates, extinct and recent,
to those of the other hemisphere, offer an inviting topic, but it
is not in my present province to discuss them in their most
suggestive phases. As we have here the oldest and most
generalized members of the group, so far as now known, we
may justly claim America for the birth-place of the order.
That the development did not continue here until it culmi-
nated in Man, was due to causes which at present we can only
surmise, although the genealogy of other surviving groups
gives some data towards a solution. Why the old world Apes,
when differentiated, did not come to the land of their earlier
ancestry, is readily explained by the then intervening oceans,
which likewise were a barrier to the return of the Horse and
Rhinoceros.

Man, however, came ; doubtless first across Behring's
Straits ; and at his advent became part of our fauna, as a
mammal and primate. In these relations alone, it is my pur-
pose here to treat him. The evidence, as it stands to-day,
although not conclusive, seems to place the first appearance of
Man in this country in the Pliocene, and the best proof of
this has been found on the Pacific coast. During several
visits to that region, many facts were brought to my knowl-
edge which render this more than probable. Man at this time
was a savage, and was doubtless forced by the great volcanic
outbreaks to continue his migration. This was at first to the
south, since mountain chains were barriers on the east. As
the native Horses of America were now all extinct, and as the

53

early man did not bring the old world animal with him, his
migrations were slow. I believe, moreover, that his slow pro-
gress towards civilization was in no small degree due to this
same cause, the absence of the Horse.

It is far from my intention to add to the many theories ex-
tant in regard to the early civilizations in this country, and
their connections with the primitive inhabitants, or the later
Indians, but two or three facts have recently come to my
knowledge which I think worth mentioning in this connection.
On the Columbia River, I have found evidence of the former
existence of inhabitants much superior to the Indians at pres-
ent there, and of which no tradition remains. Among many
stone carvings which I saw there, were a number of heads
which so strongly resemble those of Apes, that the likeness at
once suggests itself. Whence came these sculptures, and by
whom were they made? Another fact that has interested me
very much is the strong resemblance between the skulls of the
typical Mound-builders of the Mississippi Valley and those of
the Pueblo Indians. I had long been familiar with the former,
and when I recently saw the latter, it required the positive
assurance of a friend who had himself collected them in New
Mexico, to convince me that they were not from the mounds.
A third fact, and I leave Man to the Archaeologists, on whose
province I am even now trenching. In a large collection of
Mound-builders' pottery, over a thousand specimens, which
I have recently examined with some care, I found many
pieces of elaborate workmanship so nearly like the ancient
water-jars from Peru, that no one could fairly doubt that some
intercourse had taken place between the widely separated peo-
ple that made them.

The oldest known remains of Man on this continent differ
in no important characters from the bones of the typical
Indian, although in some minor details they indicate a much
more primitive race. These early remains, some of which are
true fossils, resemble much more closely the corresponding
parts of the highest Old World Apes, than do the latter our

54

Tertiary Primates, or even the recent American Monkeys.
Various living and fossil forms of old world Primates fill up
essentially the latter gap. The lesser gap between the prim-
itive Man of America and the Anthropoid Apes is partially
closed by still lower forms of men, and doubtless also by higher
Apes, now extinct. Analogy, and many facts as well, indicate
that this gap was smaller in the past. It certainly is becoming
wider now with every generation, for the lowest races of men
will soon become extinct, like the Tasmanians, and the highest
Apes cannot long survive. Hence the intermediate forms of
the past, if any there were, become of still greater importance.
For such missing links, we must look to the caves and later
Tertiary of Africa, which I regard as now the most promising-
field for exploration in the Old World. America, even in the
Tropics, can promise no such inducements to ambitious ex-
plorers. We have, however, an equally important field, if
less attractive, in the Cretaceous Mammals, which must have
left their remains somewhere on this continent. In these two
directions, as I believe, lie the most important future discov-
eries in Palaeontology.

As a cause for many changes of structure in mammals
during the Tertiary and Post-Tertiary, I regard, as the most
potent, Natural Selection, in the broad sense in which that term
is now used by American evolutionists. Under this head, I
include not merely a Malthusian struggle for life among the
animals themselves, but the equally important contest with the
elements, and all surrounding nature. By changes in the envi-
ronment, migrations are enforced, slowly in some cases, rapidly
in others, and with change of locality must come adaptation to
new conditions, or extinction. The life-history of Tertiary
mammals illustrates this principle at every stage, and no other
explanation meets the facts.

The real progress of mammalian life in America, from the
beginning of the Tertiary to the present, is well illustrated by
the Brain-growth, in which we have the key to many other
changes. The earliest known Tertiary mammals all had very

small brains, and in some forms this organ was proportionally
less than in certain Eeptiles. There was a gradual increase in
the size of the brain during this period, and it is interesting to
find that this growth was mainly confined to the cerebral
hemispheres, or higher portion of the brain. In most groups
of mammals, the brain has, gradually become more convoluted,
and thus increased in quality, as well as quantity. In some,
also, the cerebellum, and olfactory lobes, the lower parts of the
brain, have even diminished in size. In the long struggle for
existence during Tertiary time, the big brains won, then as
now ; and the increasing power thus gained rendered useless
many structures inherited from primitive ancestors, but no
longer adapted to new conditions.

Another of the interesting changes in mammals during Ter-
tiary time was in the teeth, which were gradually modified
with other parts of the structure. The primitive form of tooth
was clearly a cone, and all others are derived from this. All
classes of vertebrates below mammals, namely, Fishes, Amphi-
bians, Reptiles, and Birds, have conical teeth, if any, or some
simple modification of this form. The Edentates and Ceta-
ceans with teeth retain this type, except the Zeuglodonts, which
approach the dentition of aquatic Carnivores. In the higher
mammals, the incisors and canines retain the conical shape, and
the premolars have only in part been transformed. The latter
gradually change to the more complicated molar pattern, and
hence are not reduced molars, but transition forms from
the cone to more complex types. Most of the early Tertiary
mammals had forty-four teeth, and in the oldest forms the
premolars were all unlike the molars; while the crowns were
short, covered with enamel, and without cement. Each stage
of progress in the differentiation of the animal was, as a rule,
marked by a change in the teeth ; one of the most common
being the transfer, in form at least, of a premolar to the molar
series, and a gradual lengthening of the crown. Hence, it is
often easy to decide from a fragment of a jaw, to what horizon
of the Tertiary it belongs. The fossil Horses of this period,

56

for example, gained a grinding tooth, for each toe they lost,
one in each epoch. In the single-toed existing horses, all the
premolars are like the molars, and the process is at an end.
Other dental transformations are of equal interest, but this
illustration must suffice.

The changes in the limbs and feet of mammals during the
same period were quite as marked. The foot of the primitive
mammal was doubtless plantigrade, and certainly five-toed.
Many of the early Tertiary forms show this feature, which is
still seen in some existing forms. This generalized foot became
modified by a gradual loss of the outer toes, and increase in
size of the central ones ; the reduction proceeding according to
systematic methods, differing in each group. Corresponding
changes took place in the limb bones. One result was a great
increase in speed, as the power was applied so as to act
only in the plane of motion. The best effect of this speciali-
zation is seen to-day in the Horse and Antelope, each repre-
senting a distinct group of Ungulates, with five-toed ancestors.

If the history of American Mammals as I have briefly
sketched it, seems as a whole incomplete, and unsatisfactory,
we must remember that the genealogical tree of this class has its
trunk and larger limbs concealed beneath the debris of Meso-
zoic time, while its roots doubtless strike so deeply into the
Paleozoic that for the present they are lost. A decade or two
hence, we shall probabty know something of the mammalian
fauna of the Cretaceous, and the earlier lineage of our existing
mammals can then be traced with more certainty.

The results I have presented to you are mainly derived
from personal observation ; and since a large part of the higher
vertebrate remains found in this country have passed through
my hands, I am willing to assume full responsibility for my
presentation of the subject.

For our present knowledge of the extinct Mammals, Birds
and Eeptiles of North America, science is especially indebted
to Leidy, whose careful, conscientious work has laid a secure

57

foundation for our vertebrate palaeontology. The energy of
Cope has brought to notice many strange forms, and greatly
enlarged our literature. Agassiz, Owen, Wyman, Baird,
Hitchcock, Deane, Emmons, Lea, Allen, Gibbes, Jefferson,
DeKay, and Harlan, deserve honorable mention in the history
of this branch of science. The South American extinct verte-
brates have been described by Lund, Owen, Burmeister, Ger-
vais, Huxley, Flower, Desmarest, Aymard, Pictet, and Nodot.
Darwin and Wallace have likewise contributed valuable infor-
mation on this subject, as they have on nearly all forms of life.

In this long history of ancient life I have said nothing of
what Life itself really is. And for the best of reasons, because
I know nothing. Here at present our ignorance is dense, and
yet we need not despair. Light, Heat, Electricity, and Magnet-
ism, Chemical Affinity and Motion, are now considered different
forms of the same force ; and the opinion is rapidly gaining
ground that Life, or vital force, is only another phase of the
same power. Possibly the great mystery of Life may thus be
solved, but whether it be or not, a true faith in Science knows
no limit to its search for Truth.

QE Marsh, Othniel Charles
8*+l Introduction and
M3 succession of vertebrate
life in America

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