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DISTRIBUTION AND ORIGIN
OF LIFE IN AMERICA

_ DISTRIBUTION AND
' ORIGIN OF LIFE IN
AMERICA

BY

ROBERT FRANCIS SCHARFF

Ph.D., B.Sc.

Author of ‘* European Animals, theiy Geological History and. Geographical Distribution.”’

Corresponding Member of the Academy of Natural Sciences, Philadelphia ;
of the Senckenberg Natural History Society, Frankfurt a|Main -
of the Linnean Society of Bordeaux; and of the
Anthropological Society of Paris

LONDON

CONSTABLE & COMPANY LTD
10 ORANGE STREET LEICESTER SQUARE WC
1911

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PREFACE

Tu1s volume is the outcome of the second series of ‘‘ Swiney
Lectures” on Geology which I delivered at the Victoria and
Albert Museum in London in 1908. The subject chosen for
these lectures was the ‘‘ Geological History of the American
Fauna.” Instead of publishing the lectures, like the previous
ones on the “ European Fauna,” with little alteration, I decided
to amplify and rewrite them completely. In doing so I was
enabled to bring out more clearly certain points in the
geological history of the American animals which seemed
to me of general interest. |

It is always difficult to choose a suitable title for a work of
this kind. The one I have selected is brief yet comprehen- ”
sive. At the same time, it may be urged that the origin and
distribution of Man might reasonably be expected from the
title, whereas it has been omitted in the text. This omission
is mainly due to the fact that the literature dealing with the
subject, exclusive of Man, is very extensive, while the origin
and distribution of human races in America is treated in quite
a distinct set of periodicals and books.

An important feature of my researches is the elucidation of
some of the problems connected with the cause and nature of
the ‘‘Ice Age” or ‘‘ Glacial Epoch.” There is a considerable
amount of faunistic evidence that both the Atlantic and the
Pacific oceans were closed simultaneously in the north, result-
ing in a higher temperature of these oceans and a greater
snowfall in the countries surrounding them in the north.
Similarly, if the Glacial Epoch had been due to a closing of the
Arctic Ocean, the higher temperature prevailing in the Arctic

gt oat PREFACE

area during early Tertiary times must have been caused by a
more abundant supply of warm currents in the Arctic Ocean
at that time. Consequently North America would probably
have been more isolated in the north than it is now, for the
currents must have had ample facilities for passing freely into
the Arctic Ocean. Palaeontological evidence, however, points
to an intimate union of North America and the Old World
during the greater part of the Tertiary Era. There are thus a
number of interesting problems, all of which are fully dis-
cussed in this volume, quite apart from many other important
theories arising out of the subject of the origin and distribution
of life in North America. In this connection the testimony
of fossil animals, and that of the marine fauna, has been largely
availed of. To a certain degree the distribution of plants has
also been included.

I have endeavoured, as far as possible, to quote all the more
noteworthy works and papers dealing with the subject under
consideration. Nevertheless I am conscious of having possibly
overlooked a few important contributions; and I only hope my
colleagues will be good enough to draw my attention to any omis-
sions that they may notice, so as to enable me to add them in
case a second edition of this book should be called for. I can
lay no claim to having made careful studies of the literature
_ dealing with the Geology or Botany of the American continents.
The works cited are those that I happened to be acquainted
with, and no doubt many gaps might be filled by those more
conversant with these sciences than I am.

I have hesitated for some time before actually illustrating
my views as to the former changes of land and water. Some
geologists consider it inadvisable to publish palaeogeographical
maps founded on zoogeographical data, since such maps are
very liable to revision according to the constantly advancing
state of our knowledge. The latter are also apt to lead to a
good deal of adverse criticism, for one map can only represent
a single short phase of a long series of geological ages during
which repeated changes of land and water probably took
place. In spite of these objections I have ventured to con-
struct a few of these ideal maps of ancient geography as a

PREFACE vil

general illustration of my views. I have felt that although I
am open to criticism, my views will be more easily understood,
and we shall eventually make more rapid progress in arriving
at the correct conclusions as to the alterations in the configura-
tion of the oceans and continents that actually occurred in
the past than if such maps were altogether omitted.

The immense advance that has been made in the United
States in the study of zoology has greatly facilitated my work.
And everywhere in America I found willing helpers ready to
impart information. My thanks are particularly due in this
respect to Prof. H. F. Osborn, Dr. Matthew and Dr. Hornaday
of New York, to ‘Prof. Morse and Mr. John Ritchie of Boston,
to Dr. Henry B. Bigelow and Mr. T. Barbour of Harvard
University, to the late Dr. A. E. Brown and Mr. Witmer Stone
of Philadelphia, to Dr. Dall, Dr. T. W. Vaughan, Dr. Stejneger
and Miss Richardson of Washington, to the late Prof. Packard
of Providence, to Dr. Ortmann of Pittsburg, to Dr. Van Den-
burgh of San Francisco and to Dr. Ruthven of Ann Arbor.
Several of my European friends also aided me in many ways.
Among them particularly the following members of the staff
of the British Museum: Dr. Smith Woodward, who was good
enough to look through the proofs and to draw my attention
to several errors, Dr. Andrews, Dr. Boulenger, Mr. Regan,
Mr. Pycraft and Mr. B. B. Woodward. Prof. Hull, Dr. Bruce
and Dr. Stapf kindly pointed out to me various valuable
sources of information. My most grateful acknowledgment,
moreover, is due to the guardians of the Great Libraries, with-
out whose ready assistance I should never have succeeded in
accomplishing this work. The most generous facilities for
study were given me by my friends Mr. Lyster of the
National Library of Ireland, Mr. Praeger of the Royal Irish
Academy Library and Dr. Foord of the Royal Dublin Society’s
Library. I am indebted, too, for many services to Mr. Kappel,
the Librarian of the Linnean Society, to Mr. Jones, Librarian
of the Geological Society, Mr. Waterhouse of the Zoological
Society of London, and Mr. Hinch of the National Library of
Treland.

I am under a great obligation to Messrs. Meiklejohn & Son

Vili | PREFACE

for allowing me to reproduce two of their beautiful oroscopic
maps, while the council of the Royal Irish Academy, Prof.
Osborn, Dr. von Ihering, Dr. Ortmann, Mr. Thompson Seton,
Dr. True and Dr. Hornaday were good enough to give me
permission to copy maps illustrating their works.

I can scarcely hope that all the conclusions I have arrived
at in this book will be readily accepted, but I trust to have
succeeded in impressing those who have not made a serious
study of the science of geographical distribution of animals
with the profound importance of the subject as an aid to
palaeogeographical researches.

R. F. 8.

Tupor HovsE,
DunprvuMm, Co. DUBLIN,
November 27th, 1911.

CONTENTS

CHAPTER I

THE FAUNA OF GREENLAND

. PAGE
Description of Greenland—The reindeer and its origin—The
Arctic musk ox—The lemming and Arctic hare—On the
ancient‘ land connections between Greenland and the adjoining
continents—On the cause of the Ice Age—The marine fauna of
the North Atlantic cited as evidence in favour of a northern
land connection—Did the fauna of Greenland survive the Ice
Age in the country ?—The snails of Greenland quoted in support
of this theory—On the supposed polar origin of life—General
faunistic affinities of Greenland with other northern countries. 1-25

CHAPTER II
THE FAUNA OF NORTH-EASTERN NORTH AMERICA

Description of the general features of Labrador and its fauna—The
voles and jumping mice—On some northern frogs—The origin
and distribution of the moose deer—The fauna of the White
Mountains and its origin—Pre-Glacial relict colonies in the
North-East—Supposed effect of the Ice Age on the fauna—
Were the animals driven south by the cold ?—On mild inter-

* glacial phases of the Glacial Epoch—Foraminifera in the Glacial
drift deposits—The relict fauna of the Great Lakes—The
fishes of the Great Lakes and their origin—Distribution and
geological history of the fresh-water mussel Margaritana—The
past history of the Great Lakes—The fauna of Newfoundland 26-57

CHAPTER III
THE ANIMALS OF THE CANADIAN NORTH-WEST

The Mackenzie basin and its fauna—The lemmings and gophers
—On American ptarmigans—The past history of the bison and
its gradual destruction—On the distribution and origin of
the wapiti deer—The Canadian tree - porcupine—On the
molluscan fauna of the north-west and its relationship . 58-73

x | CONTENTS

CHAPTER IV

THE FAUNA OF ALASKA
PAGE

On the general features of Alaska, its glaciers, volcanoes and flora—
Conditions of Alaska during the Glacial Epoch—On the evidences
derived from the fossil mammals as to the former climate of
the country—Evidences of an Asiatic invasion of animals into
Alaska—The faunistic affinities of Alaska--On the former
presence of the mammoth in Alaska—The fresh-water fishes of
Alaska—The distribution and origin of the butterflies belonging
to the genus Parnassius—-On the mammals peculiar to Alaska—
On the relationship of the marine mollusks of the northern
Pacific in recent and past times—EHvidences of a former land
bridge near Bering Strait . . ‘ i " : - 74-100

CHAPTER V
THE ROCKY MOUNTAINS AND THEIR INHABITANTS

The region of the Great Salt Lake—Distribution and origin of the
mountain sheep and Rocky Mountain goat—On the geological
history of the American deer tribe—the prong-horn antelope
and its origin—On the Rocky Mountain flora—Accidental
distribution as applied to butterflies— Description of the
American game preseryes—The great Tertiary deposits and
their contents . ‘ ‘ ‘ - : ; . 101-122

CHAPTER VI
THE ANIMALS OF THE EASTERN STATES

On the poverty of lizards in this region—The snakes of the eastern
states and their affinities—The origin and distribution of the
garter snakes—Rattlesnakes and their range—On American
tortoises and turtles—The giant salamanders of America and
Asia-—-On newts and their allies—The relationship of the
Eastern plants—The pine-barren flora—The range of the
star-nosed mole . ; : ; ‘ ‘ ‘ A . 123-143

CHAPTER VIL.
THE FAUNA OF THE CONTINENTAL BASIN

Description of the prairie region and its inhabitants—On the extinc-
tion of the horse in America and the geological history of the
horse tribe—Prairie dogs and their distribution—On the origin
and past history of the raccoon—On caves and their contents as
illustrating the geological history of the fauna—The former

CONTENTS xi

PAGE
presence of the reindeer south of its existing range—Evidences
of a southern fauna in the north and of its gradual southward
retreat—Helicina—Turkeys and the Florida parrot—On the
dispersal of fresh-water mussels—Relicts of the past—Bony-pike
and bow-fin—The blind fauna of America. : ; . 144-166

CHAPTER VIII
THE SOUTH-EASTERN STATES AND BERMUDA

On the vegetation and general features of Florida—The geological
history of Florida—On the reptiles and amphibians of the south-
east—The south-east as a centre of dispersal—The terrestrial
mollusks of Florida—On scorpions and dragon-flies—Alligators
and crocodiles, their origin and past history—The fauna of
Bermuda island—The geology and flora of Bermuda—The birds
and their origin—Terrestrial isopods, spiders and the land
nemertean worm Geonemertes—On the snails of Bermuda and
their ancestors—The origin of the Bermudan fauna . 167-195

CHAPTER IX
SOUTH-WESTERN NORTH AMERICA AND ITS FAUNA

On the so-called “Sonoran Region”—The palaeogeography of
California and the adjoining States—On the western insecti-
vores—On horned toads and burrowing lizards—Discontinuous
distribution of some western toads—The snails of California—
The fauna of lower California and its Cape region—On the
European element of the Californian fauna as illustrated by the
mollusks, butterflies and ants—The crayfishes of the south-
west and their origin—Various faunistic problems—On mam-
malian affinities—The American rabbits and their relations—
The former Atlantic land connections between the New World
and the Old, supported by the evidence derived from Tertiary
mammals-—Oonclusions . , ; ; ‘ . 196-232

CHAPTER X
THE FAUNA OF CENTRAL AMERICA

The fishes of Central America and their origin—On the geology and
palaeogeography of Central America—Importance of deter-
mining the age of Central America—LEvidence derived from a
study of the marine faunas—On the faunistic affinities between
North and South America—The flora of Central America—
Monkeys and raccoons—On birds, tortoises and snakes—The

Xii

CONTENTS ©

fresh-water crabs and their dispersal—The European element in
the fauna of Central America—On discontinuous distribution

PAGE

of animals as a proof of their antiquity . : . - . 288-260

CHAPTER XI
THE WEST INDIAN ISLANDS AND THEIR INHABITANTS

The geology of the Antilles—Palaeography as illustrated by the dis-

tribution of snails—Antiquity and dispersal of snails, their
relationship and European affinities—On the theory of the
ancient Atlantis—The problem of the supposed permanence of
ocean basins—The marine mammals of the Antilles and their
origin—Evidences in favour of a mid-Atlantic land bridge—
The terrestrial mammals of the West Indian islands—Evidences
of former changes of level in the Antillean area—The blind

animals of Cuba—On the ancient Antillean continent . 261-294

CHAPTER XII

THE FAUNA AND FLORA OF THE GALAPAGOS ISLANDS

Darwin’s visit to the islands and his views on the origin of their

animals and plants—On accidental dispersal—The birds,
tortoises and snails of the Galapagos islands—Origin of the
flora—Baur’s criticisms of Darwin’s views-—Euphorbia and
its past history—Conclusions as to the origin of the Galapagos
fauna—The geological history of the Pacific Ocean—On the

7 supposed former Pacific continent—Mr. Guppy’s researches—

x

Coral reefs and their history—A circum-Pacific land belt—
Evidences of ancient lands westward of Central America—On
faunistic affinities between the Atlantic and Pacific oceans—

The Humboldt current . ; 4 : ' : . 295-835

CHAPTER XIIT

THE ANIMALS OF THE NORTH-WESTERN STATES OF SOUTH AMERICA

The geological history of South America—The faunal elements of

the continent—Palaeontology—Course of development of the
continent during the Tertiary Era—Peripatus and its distribu-
tion in South America—On the origin of Clausilia and its
relations—The South American bear—On the tapirs and their
origin—The dwarf deer of South America—On the supposed
existence of former land connections—Derivation and history

of the fossil elephants—The river Amazon : : . 836-362

CONTENTS xiii

CHAPTER XIV

THE FAUNA OF EASTERN SOUTH AMERICA
PAGE

South American monkeys, their distribution and geological history
—Sloths—The birds of South America—On fossil mammals and

Old World affinities—The theory of an ancient land connection

X between South America and Africa—Evidence derived from
the distribution of reptiles, amphibians, fishes, mollusks and
fresh-water crabs—Dr. von Thering’s researches—Fernando de
Noronha and St. Helena-—The fauna of St. Helena and its
eeraly ran § da Cunha . , ; ; . 863-394

CHAPTER XV
ARGENTINA AND CHILE

The fauna of Argentina—Prof. Ameghino’s discoveries of fossils
and their importance—Fossil edentates and rodents—Faunistic
affinities—The llama and its origin—Fossil elephants—Ancient
land connections between South and North America—Fossil
plants — Floral affinities—The circum-Pacific land belt—
Antarctic problems—On the Antarctic continent—Affinities
of the faunas of Patagonia and New Zealand—On a Pacific
continent—The marine fauna of Patagonia—The Falkland
islands—Antarctic expeditions—The pendulation theory 395-435

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LIST OF ILLUSTRATIONS

. Map of North America (reproduced from Meiklejohn’s oro-

scopic maps by permission of Messrs. Meiklejohn & Son)

. Map of the North Atlantic, showing the supposed conditions

of land-and water during later Pliocene times (reproduced by
permission of the Council of the Royal Irish Academy)

. Map of North America, showing the distribution of the Moose

Deer (reproduced by permission of Mr. Thompson Seton)

. Map showing the outlines of the White Mountain Plateau and —
Mount Washington, with an inset Map of North America

indicating the geographical position of the White Mountains

. Map of North America showing the original distribution of the

Bison, the range of the same species after the completion of
the Union Pacific Railroad and its present range sniciagiiy
by permission of Dr. Hornaday) ;

. Map of North America, showing the original distribution of the

Wapiti deer, and its range in 1900 (reproduced ty! permission
of Mr. Thompson Seton) . :

. Map of the northern parts of the northern hemisphere,

showing the supposed land connections and the extent of the
sea in the early part of the Glacial Epoch

. Map of the World, indicating the distribution of the newt

Spelerpes

. Map of North America, aise the distribution of the Star-

nosed Mole (reproduced by permission of Dr. True)

Map of North America, showing the distribution of the Rein-
deer (reproduced with some modifications by aparece of
Mr. Thompson Seton)

Map of North and South scantsne sees the distribution of
the snail Helicina .

Map of the World, showing the distribution of the ae of
fishes Cichlidae (reproduced by permission of Mr. Tate Regan)

PAGE

16

32

36

65

67

98

138

142

155

158

234

15.

16.

17.

18.

19.

20.

21.

“LIST OF ILLUSTRATIONS

. Map of the West Indian ee ae the — of the

principal islands

. Map of North and South America, sadloating Baie the

supposed conditions of land and water about the commence-
ment of the Tertiary Era

Map of the World, showing the conditions of land and water
in upper Cretaceous times according to Dr. Ortmann (repro-
duced with the author’s permission)

Map of North and South America, indicating roughly the
supposed conditions of land and water about the middle of
the Tertiary Era

Map of the World, showing the conditions of land and water
during the Eocene Period, according to Dr. von Ihering
(reproduced with the author’s permission)

Map of South America (reproduced from Meiklejohn’s oroscopic
maps, by permission of Messrs. Meiklejohn & Son) ;

Map indicating the distribution of the snail Clausilia in the
Mediterranean region, in Africa and America, with an inset
figure of Clausilia (Nenia)

Map of the World, showing the conditions of land and water
in lower Tertiary times, according to Dr. Ortmann (repro-
duced with the author’s permission)

Map of the World, showing the conditions of land and water
in late Cretaceous and basal Eocene times, according to
Professor Osborn (reproduced with the author’s permission)

PAG

262

280

292

294

314

336

349

382

419

—

= Highland over 1000 Feet.

Upland under 1000 Feet.
j Lowland under 600 Feet.

le 105 90

Fic. 1.—Map of North America. (Reproduced from Meiklejohn’s Oroscopic
Map, by permission of Messrs. Meiklejohn & Son.)

[ Zo face p. 1.

Distribution and Origin
of Life in America

CHAPTER I
THE FAUNA OF GREENLAND

GREENLAND geographically belongs to arctic America
rather than to Europe, and, as it no doubt formed part of the
land bridge that once connected America and Europe, its past x
history contains chapters of the greatest interest. Scanty
as the fauna and flora of Greenland are, they afford us many
a clue as to former changes of land and water which that
country has undergone. ‘Their study enables us also to trace
the origin of the animals and plants of the neighbouring por-
tion of continental America, which is one of the objects of
the present work. .

Greenland is now too well known to need a long description.
Yet few readers realise the vast size of this stern and
uninviting country, which covers an area considerably larger
than the whole of France and Germany together. ‘Three-
quarters, at least, of this area being completely buried
under an enormous glacier ice-sheet, or inland ice, only a
comparatively narrow belt of partly barren rocky ground is
left along the shore on which animal and plant life is possible.
The broadest exposed strip of land on the west coast of Green-
land is about a hundred miles wide. Here and there two
kinds of willows and the dwarf birch together form scrubby
low-growing woods, the stems rarely rising more than a few
feet from the ground. Thickets of alder, white birch and
dwarf juniper likewise occur, while in sheltered nooks the

L.A. B

2 ORIGIN OF LIFE IN AMERICA

Lapland rhododendron, many kinds of saxifrages, cinquefoil,
crowfoot, a willow-herb, a lousewort, the narrow-leaved arnica
and other flowering plants for a time infuse variety into the
brownish-grey landscape, giving it quite a gay appearance
with the many brightly-coloured blossoms. During a couple
of weeks in the short summer the natives may even have the
advantage of gathering crow-berries (Empetrum nigrum),
which grow in great abundance almost everywhere, just as
they do in boreal America and Europe. ‘The bilberry and
cowberry are also noticeable, but they are less common and
do not seem to be used by the natives, nor is the cloudberry,
whose fruit rarely ripens. All these are well-known American
and HKuropean plants. The most valuable vegetable, which is
largely used for food, is a tall angelica. It sometimes attains
a height of six feet in favourable localities.

During early Tertiary times many species of conifers and
several of our common deciduous oaks, poplars, walnuts,
maples, lindens, magnolias and beeches flourished in Green-
land. Many of the same trees also lived in Iceland, Spits-
bergen, Grinnell Land, boreal North America and the New
Siberian islands. It is evident that the climate all round
the Arctic Ocean must have been mild. Many causes have
been assigned for the change from the former temperate
climatic conditions to the arctic ones now prevailing in the
same region. A less restricted circulation of warm ocean
water into the circumpolar area might, as has been suggested,
help to bring about such a state. Yet it would not alone be
sufficient. Sun and light for a longer period than now obtains
would seem to have been necessary to ripen the wood of the
trees and bring the fruit to maturity. At any rate, all this
luxuriant flora must have disappeared from these northern
regions long before the Ice Age. It is quite possible, and I
even think it probable, that many of our common arctie and
alpine plants originated in these remote Tertiary times. I
cannot adduce any direct geological evidence for such a belief,
since few of these plants possess properties which would
enable the remains of their leaves to be preserved in a fossil
condition. The assumption is founded chiefly on their wide
geographical distribution.

As I am dealing mainly with faunistic problems, the

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REINDEER AND ITS ORIGIN 8

animals of Greenland have to be considered more in detail. It
is especially the beasts or mammals that are of importance
because their distribution and geological history are better
known than those of the smaller animals. They also enable
us to readily appreciate the more recent changes in the fauna,
and the causes which have led to them.

The most noteworthy and best known of the Greenland
mammals is the reindeer. The term reindeer (Rangifer
tarandus) is employed for the sake of convenience in its wide
sense. In America it has been the custom for many years
past to distinguish under the names of “ barren-ground
caribou,” and ‘‘ woodland caribou” two strikingly different
forms which occur on the continent, the term “ caribou ”
being probably derived from the Indian word ‘“ maccaribo.”
Not only have these two kinds of 'reindeer dissimilar habits,
they also differ from one another in size, and in the structure
of their skulls and antlers. More recently, smaller groups of
reindeer have been discovered, showing distinctive characters
in their antlers alone. Several of the nine forms thus
recognised as American are founded upon comparatively
slight differences. An illustrated account of these various
American reindeer has been given by Mr. Madison Grant.*

Mr. Lydekker + holds that they and the Old World forms
are all referable to one single species, of which he distin-
guishes six varieties. Whether these differences are to be
regarded as specific or varietal is a matter of opinion, but,
as the antlers of reindeer are so very variable, it has been
suggested by Professor Camerano that the structure of the
skull might be utilised to greater advantage in discriminating
between the various varieties or species. In his researches
on the Spitsbergen form, he argues that there are three
species, viz., the reindeer of Spitsbergen (R. spitsbergensis),
the one inhabiting Greenland, Norway, Lapland and part of
Siberia (R. tarandus), and lastly the American reindeer (R.
caribou). Among the last two species he distinguishes again
between the reindeer possessing cylindrical (cylindricornis)
and those having compressed (compressicornis) antlers.

It is worthy of note that the reindeer of Scandinavia and

* Grant, Madison, ‘‘ The Caribou.”
+ Lydekker, R., ‘‘ The Deer of all Lands,” p. 33.
BQ

4 ORIGIN OF LIFE IN AMERICA

Greenland constitute a single variety, according to Professor
Camerano,* while Mr. Lydekker separates the Scandinavian
from the Greenland race. Following Professor Camerano’s
example, Dr. Lénnberg + prefers the nasal bones of the skull,
to the antlers for specific diagnosis. He unites the Greenland,
Spitsbergen and Scandinavian forms with the American
barren-ground reindeer in one group, characterised by their
flat nasals. The Finland and Siberian reindeer he holds to
be quite distinct races, particularly the former, which, with
its elevated nasal bones and somewhat flattened antlers, ap-
proaches the American woodland caribou. Even Robert
Brown { long ago commented on the likeness of the Green-
land and Kuropean reindeer, remarking that some reindeer
horns from Greenland could not be distinguished from
European ones. Since Professors Camerano and Lénnberg,
moreover, take both skull characters and antlers into con-
sideration, we may assume that this view of the affinity of the
Greenland to the north-west European race is likely to be the
correct one.

An anonymous writer in “Natural Science,” (p. 358,
1899) gave it as his opinion that there are no grounds for
deciding whether the Old or the New World was the original
home of the reindeer. No doubt he meant to convey that we
know nothing of the ancestry of the reindeer. I ventured, §
on the contrary, to put forward the theory that the reindeer
had originated in the Polar area, beyond the confines of the
European Continent, while Professor Schlosser || argued that
it was evidently of American origin. Neither of these views
is supported by positive geological evidence; nevertheless
- I cannot agree with the above critic that we possess no grounds
for deciding the place of origin of the reindeer, as the results
of Professor Camerano’s and Professor Lénnberg’s cranial
researches seem to indicate the existence of a closer rela-
tionship between the west European and the Greenland and

* Camerano, L., ‘‘ Renne delle Isole Spitzberge,’”’ p. 167.

{| Lonnberg, Einar, ‘Taxonomic Notes about Reindeer,” p. 10.

t Brown, Robert, “ Mammals of Greenland,’ p. 352.

§ Scharff, R. F., ‘“‘ History of European Fauna,” p. 155.

|| Schlosser, M.,‘‘ Beziehungen d. ausgestorben. Siugethier-faunen,”
p. 617.

—s. oe ae a oe

REINDEER AND ITS ORIGIN 5

arctic American varieties than between the west Huropean
and the Siberian reindeer. The assumption that the species
originated in Greenland or arctic America and thence spread
along old land connections east and west to Hurope and Asia,
is, therefore, not quite so unjustifiedias Dr. Stejneger * seems
to think.

But we must not forget the possibility of the reindeer

ie ‘having originated in the Old World. Dr. Brown? argues

that the barren-ground variety .spread to America from
western Europe by way of a Spitsbergen-Greenland land
connection, while the other traversed Siberia, and crossed to
the New World by Bering Strait. In the more southern
parts of its range in America, new varieties may have
arisen, perhaps owing to changes in the natural sur-
roundings. Long cylindrical antlers were no doubt a dis-
advantage to reindeer in wooded districts, hence the beam
became reduced in length and increased in width in what is
known in America as the “ woodland caribou.” Some of these
varieties, or species as many American naturalists choose to
call them, intergrade to such an extent as to be difficult to dis-
criminate from one another. Thus Rangifer stonei is a form
of barren-ground reindeer living in Alaska, while Rangifer
osborni is a woodland form. Dr. Allen, who first described
them, considers them as well-marked species, while Mr.
Osgood,{ during his travels in Alaska, finds that the differ-
ences between the two are all relative, that they are excessively
variable and rather intangible. The mountain caribou (Ran-
gifer montanus), originally described by Mr. Thompson
Seton, is considered by Dr. Allen § to be allied to the wood-
land form, but distinguished from it in colour, size and shape
of antlers. Mr. Seton,|| who has published a most instructive
map of the geographical distribution of the caribou in North
America, which has furnished me with the materials for the
map given in this work (Fig. 10), thinks that in future the

* Stejneger, L., “Scharff’s History of the European Fauna,”
p. 112.
+ Brown, A. E., ‘‘ North American Big Game,” p. 87.
¢} Osgood, W. H., ‘‘ North American Fauna,” 33, p. 17.
_ § Allen, J. A., “‘ Mountain Caribou,” pp. 8 & 9.
| || Seton, E, Thompson, ‘“ Northern Animals, I.,” p, 192,

.

6 ORIGIN OF LIFE IN AMERICA

ten species now recognised in America will be reduced to
four well-marked species.

How long the caribou or reindeer has been in existence
we do not know. Its remains have been discovered both in
Kurope and America in deposits believed to have been laid
down during the Pleistocene Period, and as these occur far
to the south of its present range, it has invariably been
assumed that the species was compelled, owing to unfavour-
able climatic changes to abandon its more northerly habitat.
When the climate became once more suitable to its require-
ments, the reindeer is supposed to have returned to its, original
home. This idea suggests that the reindeer originated in
pre-Glacial times, and this view is, in my opinion, supported
by the evidence of its occurrence, conjointly with the hyaena,
in Irish cave deposits.*

The whole subject of the influence of the Glacial Epoch
on animals and plants will be dealt with later on, and need
not be considered here. The fact of the occurrence of un-
doubted reindeer remains far to the south of its present
range certainly requires an explanation, and this is more
easily given in conjunction with other facts to be stated
in this chapter. While the reindeer still lives in Europe no
further south than the fifty-second degree of latitude, in
America it is found no less than seven degrees further south.
In former times it inhabited Oregon and Kentucky. In the
east it came down to the neighbourhood of the present site
of New York City, whereas in Kurope it advanced as far as
Mentone on the shores of the Mediterranean, and penetrated
to the north of Spain, i.e., to the latitudes of the thirty-eighth
degree in America and of the forty-third degree in Kurope.f

The musk ox (Ovibos moschatus) is another even more
arctic mammal than the reindeer. So called from the musky
odour of its flesh, this species was believed to be more closely
allied to the sheep than to the ox, which it resembles more in
size. In its geographical distribution it differs strikingly
from that of the reindeer in so far as it is now quite confined
to Greenland and arctic North America. It no longer inhabits

* Scharff, R. F., ‘‘ European Animals,” p. 112.
t+ Brauer, A., ‘‘ Die arktische Subregion.”

——————— a pl wal

ARCTIC MUSK OX 7

the Old World. Yet in Europe it penetrated as far as England
and France in Pleistocene times, having apparently reached
these countries from an eastward direction. While the rein-
deer occurs even in southern Greenland, the musk ox
frequents only the north and east of that country.

According to Dr. Conwentz, it has only wandered east-
ward from the north coast of Greenland in recent times.
At any rate, Professor Nathorst alleges that Scoresby, in the
year 1822, did not observe it in the neighbourhood of the
Sound which bears his name, though it is now found there.
Nevertheless, the discovery of some very ancient skulls
between the seventieth and seventy-fifth degrees of latitude
on the same coast make it probable that the musk ox lived
in that region in more remote times, afterwards becoming
extinct only to advance once more to its former habitat in
recent times.*

The musk ox to most observers has appeared to be subject to
little variation. Mr. Lydekker, however, described a form
from eastern Greenland (Ovibos moschatus wardi) with a
whitish face-patch and lighter general colouration, which
Dr. Allen + has since raised to specific rank, showing that it
also differed from the type in the structure of the horns and
hoofs. The latter likewise pointed out that it was not con-
fined to Greenland, but inhabited also Ellesmere and Grinnell]
Land.

Another form of musk ox, an almost black one, from the
far north of Canada, was first noticed and described by Mr.

Elliot. A renewed examination of musk ox skins and skulls

was recently undertaken by Dr. Kowarzik{ with rather re-
markable results. He recognises two strikingly distinct
groups of musk oxen, a western and an eastern group,
characterised by very important osteological and external
features, which had apparently escaped the attention of pre-
vious observers. In a private letter he admitted to me
that the musk ox must have originated in North America,
Bodtherium being probably its direct ancestor. Yet he is
evidently inclined to believe that, after spreading by way of
* Conwentz, “ Verbreitung d. Moschusochsen,” pp. 429—481.

+ Allen, J. A., ‘‘ Musk-Oxen of Arctic America,” p. 76.
{ Kowarzik, R., ‘‘ Der Moschusochs,” p. 120.

.

8 ORIGIN OF LIFE IN AMERICA

Asia to Europe, it became extinct in America as well as in
Greenland. |

Part of one section of the old musk ox stock returned to
North America by way of Asia, while another travelled by
means of a north Atlantic land connection to southern Green-
land, gradually finding its way along the eastern and western
coasts to northern Greenland. Meanwhile the musk ox had
entered Alaska again from Asia and crossed the Mackenzie
River into arctic Canada, where some of the peculiar forms
originated.

Dr. Kowarzik promises us further contributions to this
interesting problem from a palaeontological point of view.
These will be of particular value in elucidating the question
of the relationship between the European and the Greenland
forms of the musk ox. I agree in so far with Dr. Kowarzik,
as I feel convinced that the musk ox originated in North
America in pre-Glacial times, but I differ in most of his other
views. If land connections existed between North America
and Asia, and between North America and Europe, they must
have persisted through Pliocene to early Pleistocene times.
I am of opinion, therefore, that the musk ox spread east-
ward to Europe and westward to Asia as long as land
bridges enabled it to do so. It is quite possible that the
Asiatic section subsequently travelled westward to Kurope,
but neither of them succeeded in returning to their native
land. The musk oxen we find in Greenland and arctic
America, probably survived the Ice Age where they now
live. This opinion has the support of Dr. F. Wright* and
Professor Upham as the result of their special study of the
geological history of Greenland.

Not long ago the musk ox was still found in Alaska. Now
it has been quite exterminated west of the Mackenzie River.
As Dr. Allen remarks, the genus Ovibos is a declining type,

which has attained its last stronghold in the arctic barren

grounds. Wherever it is within the grasp of man it will
soon be a creature of the past.

We possess no undoubted evidence of the existing species
of musk ox having ever penetrated as far south as the United
States, nevertheless it is quite possible that the fragmentary

* Wright, F. F., and Warren Upham, ‘“ Greenland Icefields,”’ p. 332.

» es ee

OO VO eee
Cala —

LEMMING AND ARCTIG HARE ~ 9

remains which have been discovered in caves and other super-
ficial (Pleistocene) deposits in Pennsylvania, Kentucky, Mis-
souri, lowa and Ohio may have belonged to varieties of Ovibos
moschatus rather than to extinct species of musk oxen.

There are two other arctic mammals which are of special
interest to us, since both of them inhabit Greenland. They
are the arctic hare (Lepus variabilis = L. timidus) and the arctic
lemming (Dicrostonyx torquatus = Cuniculus torquatus).

Like the reindeer, the arctic hare is subject to great varia-
tion over the vast area which it inhabits, and some of these
varieties or races are now recognised by many zoologists as
species. Mr. R. Brown™* long ago felt the difficulty, nay,
almost impossibility, in discriminating between the Green-
land hare and the arctic or varying hare of Hurope. The same
embarrassment has confronted many subsequent authors. In
America the Greenland hare is now generally considered as
specifically distinct from the arctic American hare, Mr.
Rhoads + having pointed out some important features in its
incisor teeth, while Mr. Nelson { finds that its excessively
heavy wool-like coat of fur, the long claws and tapering upper
mandible sufficiently distinguish it from its relatives on the
American Continent to give it the rank of separate species.
However, as Mr. Rhoads aptly remarks (p. 356) the peculiar
dentition, long fur, and long claws are due partly to the
scantiness and character of plant life, and partly to the depth
and long continuance of the snow in Greenland. These fea-
tures seem to have gradually impressed themselves on the
Greenland hare in modifying it in the direction indicated.
In Major Barrett-Hamilton’s § opinion the chief differences
between the European arctic hares and the Greenland form,
from an external point of view, are only of a sub-specific
value, while Dr. Winge || does not specifically distinguish the -
American or Kuropean arctic hares from the Greenland one.

The same problem of affinity has recently been investigated
from a new standpoint by Mr. Hinton. His researches have

* Brown, R., ‘“ Mammals of Greenland,” p. 351.

+ Rhoads, 8. N., “ Polar Hares of North America,” p. 368.
t Nelson, E. W., ‘‘ Rabbits of North America,” p. 68. .

§ Barrett-Hamilton, G. EK. H., ‘‘ The Variable Hare,” p. 92.
|| Winge, H., “‘Grénlands Pattedyr,” p. 376,

10 ORIGIN OF LIFE IN AMERICA

led him to a comparison of the fossil hare remains from the
ossiferous fissures of Ightham in England with the recent
polar or arctic hares as a whole. He has been exceptionally
fortunate in disposing of large osteological collections, and
his conclusions are of particular interest and of much value
in elucidating some important zoogeographical problems.
Dwelling upon the close affinity existing between the English
fossil and the Irish living arctic hare, he regards the latter
as the direct descendant of the former. I should not have
mentioned these particulars except that they give rise to far-
reaching deductions. From the fact of the fossil English and
recent Irish forms being the least specialized members of the
whole group of arctic hares, Mr. Hinton concludes that it is
highly improbable that the group can have had a boreal
origin.*

That the Irish arctic hare has always lived in Ireland under
temperate conditions is an opinion which I expressed long
ago in my works on the European fauna, and in this view Mr.
Hinton concurs. But I also believe, as I shall endeavour
to demonstrate later on, that even southern Greenland and
all the lands surrounding the north Atlantic had a milder
climate during the Pleistocene Period. It is principally the
climate of arctic America and Greenland, I think, that be-
came much more unfavourable within recent geological times,
while that of the British Isles has undergone comparatively
little alteration. Meanwhile specialization among the animals
constituting the Greenland fauna probably proceeded at a
more rapid rate than in Ireland, where the hare had no need
to become adapted to different ‘conditions of food ‘and tempera-
ture. In spite of Mr. Hinton’s argument, I still believe in the
arctic origin of the group in Pliocene times, mainly because I
do not admit that we have any evidence for the assumption
that Ireland was connected with Great Britain during or
after the Pleistocene Period. Mr. Hinton thus differs from
me in regarding Central Asia as the centre of origin of the
arctic hares in Pleistocene times. 7

I mentioned that the banded lemming (Dicrostonyx tor-
quatus) was found in Greenland. Of late years it has been

* Hinton, M. A. C., “The fossil hare of Ightham,”’ pp. 263—264.

a ee ee

PRT go Ee IY RTA ALTRI OF DE FOE I aa POY a DON ORE De RE SETA II

ANCIENT LAND CONNECTIONS 11

customary to distinguish the New World form (D. hud-
sonius) from the Old World banded lemming (D. torquatus),
but they are very closely allied. Several varieties of the
former inhabit the mainland and islands of arctic America,
including the north and east coasts of Greenland. The
whole genus Dicrostonyx (Myodes), is confined to the Arctic
Regions. As in the case of the reindeer and other arctic
species, we possess fossil testimony of a former southern
extension of the range of the banded lemming in Hurope.*
It occurred in Central Europe, and also in England and
Ireland, yet, as far as we know, it never penetrated into the
United States in Pleistocene times. Thatthe banded lemming
is not a recent immigrant to Greenland, but has persisted
there from pre-Glacial times seems to be indicated by the
fact that Colonel Feilden + discovered its remains, with those
of the reindeer and musk-ox, in post-Tertiary (Pleistocene)
deposits from sea-level to an altitude of 1,000 feet in northern
Greenland.

There are a couple of other mammals in Greenland, viz:
the arctic wolf and the arctic fox, which need not be specially
considered here. Nevertheless, a significant factor in connec-
tion with one of these carnivores has been pointed out by
Major Barrett-Hamilton and Mr. Bonhote.{ It is that the
arctic fox (Vulpes lagopus) of Spitsbergen, Novaya Zemlya
and Iceland agrees with that from eastern Greenland, form-
ing a variety distinct from those of the European and
American mainlands. |

All the mammals alluded to as inhabiting Greenland, live
also in Europe in identical or closely allied forms, or did so in
former times. Hence it is permissible to argue that a land-
connection once bridged over the intervening ocean. The
affinity between Greenland and arctic America in some
respects is even closer than that between Greenland and
Europe. Only the narrow Davis Strait and the still narrower
Kennedy Channel separate the two countries. Another

* Scharff, R. F., G. Coffey, and others, ‘‘ Caves of Kesh,” p. 196.

Tt Feilden, H. W., and C. H. de Rance, ‘Geology of Arctic Coasts,”
p. 566.

} Barrett-Hamilton, G. E. H., and I. L. Bonhote, “ Sub-species of
Arctic Fox,” p. 288.

12 ORIGIN OF LIFE IN AMERICA

sound of inconsiderable width, Bering Strait, divides arctic
America from the Asiatic Continent. We can easily imagine
what a comparatively small change in the configuration of
land and water would thus bring Greenland into direct touch
with Asia, by way of arctic America (compare Fig. 1).

It has actually been suggested by several writers that the
faunal relationship which exists between Greenland and
Europe is due to former land bridges across Bering Strait
and Davis Strait, facilitating the passages of animals from
Europe by way of Asia. That such land connections really
; existed in recent geological times, I do not doubt, and they
_ will be further described in this and one of my next chapters.
| Still, their existence does not preclude the possibility of
Greenland having likewise been connected by land directly
with Europe. A close relationship exists between some of the
western Kuropean and Greenland mammals. In some in-
stances that affinity is no longer apparent in the recent
mammalian fauna, but can be demonstrated to have once been
a prominent feature. The extinct Irish reindeer for example,
clearly indicates, in the character of its skull and antlers,
that it was closely related to the present Greenland and arctic
American races of reindeer, thus suggesting the former
existence of some more direct means of transit from Green-
land to Ireland, or vice versa, than by the circuitous route
across Hurope, Asia and arctic America. Many authorities,
indeed, have on other grounds insisted upon the former
presence of a land bridge uniting Scotland, the Farées,
Iceland and Greenland, with America.

The story of the extermination of the iiviganoei: reindeer
in Iceland in the twelfth century is too vague to be of much
use in connection with these researches. It appears certain,
at any rate, that no reindeer had inhabited Ié¢eland for some
hundreds of years before the end of the eighteenth century,
when the ancestors of the present stock were brought over
from Finmark. The assumption of the existence of such
a land connection as that referred to, in Pliocene, and perhaps
early Pleistocene times, or, in other words, just before and
during the béginning of the Glacial Epoch, is generally based
upon other ground than the distribution of mammals. I have
recently collected the various sources of evidence in favour

GREENLAND-EUROPE LAND BRIDGE 13

of the theory from the oceanographical, geological and
biological standpoints.* —

A second land bridge apparently united northern Greenland
and Lapland at about the same time. This I described on a
previous occasion. It will not be necessary for me to repeat
all the arguments I advanced for and against the hypothesis,
and I must content myself with a short statement of the main.
facts. The theory of the Greenland-Iceland-Scotland land
bridge (Fig. 2) had been put forward by quite a number of
authorities on independent grounds. Yet while some maintain
that it merely existed in early Tertiary times, others contend
that it couldionly have been made use of by the members of our
present fauna and flora after the Glacial Epoch, because the:
latter had not yet come into existence before that time.

One of the most important facts in favour of the existence of
this land bridge is presented, in my opinion, by the geographi-
cal distribution of the land snail known as Helix hortensis.
I have quoted many other instances in my paper on this
subject, but this no doubt affords the most striking biological
support for the belief in a land connection between Scotland,
Iceland, Greenland and Labrador.
® Helix hortensis is a typically west European species, being
quite unknown in the eastern parts of Europe or in Asia.
Beyond the mainland of Europe we find it in Great Britain,
in Ireland, the Shetland Islands, the Fardes, Iceland, in
southern Greenland, Labrador, the islands off the north-east
coast of North America, and part of the opposite mainland.

Biologists are often too ready in invoking human agency
when endeavouring to explain the occurrence of certain
common Huropean species in unexpected localities abroad.
When this snail was first discovered in North America, its
presence there was universally attributed to the action of man,
and was often cited as a good ‘instance of the facility with
which terrestrial mollusks are introduced into foreign coun-
tries and become established there. Until the year 1864 no
other theory was even thought of. During that year, however,

* Scharff, R. F., ‘“‘On a former Land Bridge between Europe and
North America.”

et od

14 - ORIGIN OF LIFE IN AMERICA

Professor E. Morse first discovered the shell of this snail
among the contents of ancient ‘ kitchen-middens,” those
peculiar refuse heaps of primitive man, on some of the islands
off the east coast of Maine. He pondered over this singular
mystery and finally came to the conclusion that the snail must
have slowly wandered, during a long series of centuries, from
the Old World to the New, by means of an ancient North
Atlantic land bridge. Mr. Johnson,* to whose instructive
paper I am indebted for this information, states that Dr.
Binney and Professor Cockerell concurred in Professor
Morse’s opinion. He also informs us that the Rev. Winkley
and he were of opinion that the arrival of the snail Helix
hortensis in America must have taken place before the advent
of the Glacial Epoch.

This theory, as can be imagined, was by no means gene-
rally accepted in America. All doubts, however, as to
the claim of Helix hortensis being an indigenous American
species are now set at rest, through the discovery by
Dr. Dall? of the shell of this snail in undoubtedly Pleisto-
cene deposits in the State of Maine. Some naturalists might
still be inclined to urge that greater facilities for occasional
transport across the Atlantic may have existed in those remote
times than at present, and that the argument in support of
a land bridge is not convincing. No evidence, however, in
favour of an ocean current from Europe to North America in
Pleistocene times has as yet been brought forward, while the
conviction in the former presence of a land connection between
north-eastern America and north-western Europe is based
upon other biological observations. From a geological point
of view we can scarcely hope to be able to'determine the period
or periods during which this land bridge existed. The bathy-
metrical features of the north Atlantic, according to Pro-
fessor Hull,t Dr. Spencer § and Dr. Nansen,|| point to a pre-
Glacial elevation of the land in northern latitudes. Dr.

* Johnson, C. W., ‘‘ Distribution of Helix hortensis,”’ p. 73.

+ Dall, W. H., ‘“‘ Land and Freshwater Mollusks of Alaska,” p. 20.
t Hull, E., ‘‘Submerged Terraces and River Valleys.”

§ Spencer, J. W., ‘Submarine Valleys,” p. 224.

|| Nansen, F., ‘‘ North Polar Expedition,” p. 192.

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ON THE CAUSE OF THE ICE AGE 15

Wright * and Mr. Upham, two well-known authorities on
glacial phenomena expressed the view that the northern lands
must have been gradually elevated in Pliocene times, be-
coming continuous before the Ice Age. Further particulars
on this subject are contained in Dr. Spencer’s article + on ©
high continental elevation.

Sir Henry Howorth opposes this view, urging that Green-
land, Scandinavia, and North America were all at a much
lower level in so-called Glacial times than they are now. If
this be so, then the epeirogenic theory has no base to stand
upon. I do not think that Sir Henry Howorth’s { statement
is applicable to southern Greenland or eastern North ‘America.
At any rate, it is not contended by anyone that the high level
condition of these countries persisted during the whole of
the Ice Age.

The theory that the Ice Age or Glacial Epoch was brought
about mainly by the closing of the Arctic Ocean to the influence
of the Gulf Stream is a very tempting one. The temperature
of the Atlantic Ocean would under such conditions have been
higher than it is now, because its heat would not have been
modified by cold arctic currents, as it is at present. Southern
Greenland, Iceland, and the lands on both sides of the
Atlantic should also have had a more favourable climate than
obtains under existing circumstances, since the warm ocean
would have had considerable influence upon their climate for
a certain distance inland. There is evidence, on the Kuropean
side of the Atlantic, that, at a not very distant geological
period, and presumably at a time when the coasts of France,
south-west of England and south of Ireland were still united,
the southern fauna and flora crept steadily northward along
the ancient shore-line. That this did not take place in very
recent times is evidenced by the fact that the southern marine
shore forms of mollusks, crustaceans and other invertebrates
have a somewhat discontinuous range on the west coast of

. the British Islands, and do not occur in the English Channel

or in the southern part of the North Sea.

* Wright, G. F., and Warren Upham, “Greenland Icefields ” p. 331.
+ Spencer, J. W., ‘‘ High Continental Elevation.”
{ Howorth, H. H., ‘‘Ice or Water,” Vol. I., p. 136.

16 ORIGIN OF LIFE IN AMERICA

Hence they evidently wandered northward under different
geographical conditions than exist at present, and only main-

tain a slender hold in isolated localities, where they form’

relict colonies. I assume that this northward advance of the
- marine fauna took place in late Pliocene times when the
northern Atlantic was closed, and the temperature of the
ocean raised. As Dr. Dall wrote to me “ the Pliocene all over
the northern hemisphere was a period of warmer sea water
than the Miocene or Pleistocene.’’ My attention was also
recently drawn by Professor Morse* to the fact that even
littoral European species have extended their range across the
ocean to North America. As long ago as 1855 he received
specimens of the common European “ Periwinkle ” (Littorina
litorea) from Chaleur Bay in the Gulf of St. Lawrence. Later
on this mollusk was reported also to occur on the coast of
Nova Scotia and Labrador. It is steadily advancing now in a
southward direction, while it is becoming scarce in the north.

Dr. Ashworthy tells me that the lugworm (Arenicola
marina) which is common on the west coast of Europe is also
met with on the coasts of the Shetland islands, the Farées,
Iceland, Greenland, Labrador and Nova Scotia. It is absent
from the coasts of the Pacific Ocean. Hence he concludes
that a continuous shore-line formerly existed between the two
areas on each side of the Atlantic Ocean in which this worm
is now found. Dr. Ashworth believes that the extensive
stretch of ocean at present existing between Europe and
America forms just as much a barrier to the dispersal of
the littoral lugworm as it does to that of the terrestrial Helix
hortensis just alluded to.

Commenting on this occurrence of European littoral marine
mollusks on the north-east coast of North America, Mr. B. B.
Woodward writes to me that no other theory than that of the
previous existence and subsequent rupture of a land bridge
in the direction indicated can satisfactorily account for the
present disjointed distribution of the two divisions of the
boreal fauna. :

It was assumed by Professor Nathorst{ that a portion of

* Morse, E. S., ‘‘ Dispersion of certain Mollusks,” p. 8.

+ Ashworth, J. H., Catalogue of Chaetopoda part I.
t Nathorst, A. G., ‘‘ Pflanzengeographie der Vorzeit,” p. 267.

.
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Present land, white

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North Atlantic during later Pl

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ancient sea, black

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FAUNA OF NORTH ATLANTIC 17

the arctic flora had originated in Greenland in pre-Glacial

times and had been scattered east and west across the exist-

ing land bridges on the advent of the Glacial Epoch, during
which the maintenance of life was no longer possible in that
country.

Sir Joseph Hooker * long ago expressed the opinion that,
although many Greenland plants were possibly destroyed
during the Ice Age, the existing remnant of a much richer
flora had survived in the southern parts of the country, whence
it subsequently spread northward again.

One of the biological arguments I adduced in favour of a
former north Atlantic land bridge was derived from the well-
known fact that deposits of dead marine shallow-water species
had been dredged in deep water in various localities such as |
Rockall Bank and off the coast of Iceland. This peculiar
circumstance has been applied by several authorities in sup-
port of the theory of a gradual sinking of the land, the
shallow-water species having thus been moved to a position
in which they are no longer able to live. It is this part of
the biological argument on the land bridge theory which has
received most of the adverse criticism. Dr. Johansen,} for
instance, pointed out that the evidence derived from the
marine shallow-water shells is untrustworthy, because’ their
presence in great depths in the northern Atlantic is not due
to a sinking of the land, but mainly to various casual or
accidental activities of transport. The theory of the north
Atlantic land bridge, in so far as it is founded upon the occur-
rence of shallow-water marine shells at great depths, does
not, therefore, meet with his approval.

Similarly, Dr. Appellff ¢ insists that the most recent dis-
coveries on the “ Faréde Bank”’ are of considerable zoogeo-
graphical significance, since they are opposed in some
measure to the theory of the sinking of the land. He informs
us that among the thick layer of dead shallow shells found
on the Farée Bank living specimens of several of the species
were met with. |

* Hooker, J. D., ‘‘ Distribution of Arctic Plants,” pp. 252—245.
+ Johansen, A. C., ‘‘On the Sinking of Sea-beds,”’ p. 403.
{ Appellgf. A., ‘‘ Norwegian Fisheries,’ Vol. II., pp. 83—89.

L.A. Cc

18 ORIGIN OF LIFE IN AMERICA

No doubt this discovery provides an argument for the op-
ponents of the land bridge theory, yet we know how adaptive
certain species are to a change of conditions, and how long
they can maintain themselves under adverse circumstances.
I am not, therefore, disposed to attach too much importance
to Dr. Appell¢f’s discovery. In any case, the land bridge theory
is not dependent on the evidence alluded to.

Dr. Spethmann,* on the other hand, reiterates what we
already know, that from a purely geological standpoint there
are no positive proofs in favour of a former land bridge
between Europe and Greenland.

These seem to be the principal arguments that have been
advanced in opposition to the land bridge theory, and they,
are, in my opinion, not very formidable ones.

The question of the supposed survival of plants through
the Ice Age in Greenland is closely connected with that of
the land bridge alluded to. Whether any plants survived, and
what proportion of those previously existing, largely depends
on the nature of the Ice Age or Glacial Epoch and on the
former extension of the glaciers in Greenland. Professor
James Geikie + maintains that it is a fair assumption that
the ice of Greenland in Glacial times completely buried the
land and, perhaps, protruded beyond it. It has recently been
very clearly demonstrated, however, by the leader of the
German Greenland Expedition, Dr. E. von Drygalski,t that
the strip of land now free from ice on the west coast of Green-
land has never been entirely invaded by glaciers. No doubt
if can be proved, he remarks, that the ice in past times had
a greater extension. All the same, glaciers never reached the
cliffs and rock pinnacles which abound on all parts of the
coast land of Greenland.

No special reason can be adduced, therefore, why the pre-
sent flora of Greenland should not have survived the Ice Age
in that country, particularly as we have some grounds for the
belief that the land in parts of the Arctic Regions then stood
higher than it does now, and that consequently more land was

* Spethmann, H., ‘‘ Aufbau d. Insel Island,” p. 8.
+ Geikie, J., ‘The Great Ice Age,” p. 736.
{ Drygalski, E. von, ‘‘ Grénland Expedition,” Vol. L, p. 385.

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DID ANIMALS SURVIVE THE ICE AGE? 19

available for plant life. Indeed, Professor Vanhéffen * who
describes the plants and animals observed during the expedi-
tion, adopts this attitude. He not only believes in the survival
of the flora of Greenland through the Ice Age, but he also
argues that the great mass of the fauna is indigenous to the
country.

Though he does not deny the possibility of organisms
being accidentally carried by birds, and other occasional
means of transport, he protests against the assumption that
the fauna of Greenland, as a whole, owes its origin to such
a mode of conveyance. Dr. Brehm? quite concurs in this
view. He is convinced that the fauna of Greenland is
autochthonous. ,

It is very generally believed that the climate of Greenland
was much colder during the Glacial Epoch than it is now,
although we possess no direct evidence that it was so. A
mild climate in South Greenland during the existence of the
land bridge is implied by the fact that a number of Huro-
pean species found in north-western North America, and
which no doubt travelled by way of Greenland, have since
become extinct in the latter country.

Greenland must, therefore, have passed through a phase
during which existence became impossible for these species.
Yet, for all we know, it may be only quite recently that the
climate of Greenland has grown so inhospitable. It has been
suggested by Professor Whitney, and more recently by Sir
Henry Howorth, that the Arctic Regions enjoyed temperate
conditions during the Glacial Epoch and are only now passing
through the more severe post-Glacial stage. In view of the
accumulation of evidence pointing to a southward advance
of the Arctic fauna and flora in Pleistocene times, such a sug-
gestion may seem contrary to biological evidence. I shall
endeavour to show, however, in the next few chapters that

_ we possess a good deal of valuable testimony, principally of

a biological nature, in support of Professor Whitney’s and Sir

| Henry Howorth’s contention.

With regard to the species which I believe to have made use

* Vanhéffen, E., ‘‘Grénland Expedition,’ Vol. IT., p. 174. »
+ Brehm, V., ‘‘ Entomostraken d. Danmark Expedition,” p. 316.

o 2

20 ORIGIN OF LIFE IN AMERICA

of the ancient north Atlantic land connection, and are sup-
posed to have subsequently become extinct on the intermediate
stations between the two continents, particular attention may
be drawn to the range of the “ running beetles ” of the genus
Carabus. They are of great value in aiding us to solve pro-
blems of this nature, because, being usually found under
stones and clods of earth, they are not liable to occasional
transport by floods. Being wingless they cannot be carried
to distant lands by winds; and lacking any kind of means by
which they might become attached to a mammal or bird they
would not be conveyed in such an accidental manner from one
locality to another. The great importance of the species of
Carabus has been recognised, and their distribution brought
to bear upon zoogeographical problems by Mr. Born.* He cites
two of the species, viz., Carabus catenulatus and Carabus
nemoralis, as evidences of a former land bridge between
northern Europe and North America, although they no longer
occur in Iceland or in Greenland. Both these running beetles
are typically European species, being quite absent from Asia.
The conspicuously ornamental Carabus memoralis is confined
in North America, to Nova Scotia and New Brunswick. Hence
it somewhat agrees in its American range with that of Helix
hortensis. The other species of Carabus has a wider dis-
tribution in boreal North America.

Such instances lead us to believe, therefore, that the faunas
of Greenland and Iceland were richer in pre-Glacial times
than at present. They are certainly suggestive also of a sur-
vival of species having taken place through the Ice Age within
the glaciated area of North America. We possess no evidence
that these beetles and the snail Helix hortensis, and many
other animals belonging to the same group of European in-
vaders, were pushed south during Pleistocene times into the
United States, and that they then regained their former
northern habitat, after having become extinct again in their
more southern stations.

The extinction of a large part of the former beetle fauna
of Greenland may be inferred from the fact that Greenland
only possesses forty-one species of beetles, while there are

* Born, P., ‘* Zoogeographisch-carabologische Studien,”’ p. 8.

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THE SNAILS OF GREENLAND 21

ninety-one in Iceland.* Of the more hardy spiders the per-
centage of survival is very different, for there are fifty-three
species in Greenland and only twenty-four in Iceland.+

The theory of the survival of species in Greenland may
be tested by some other examples. Besides Helix hor-
tensis about a dozen other kinds of land and _ fresh-
water mollusks inhabit the country.[ Hight of these either
have their centre of distribution in Greenland or are
quite peculiar to the country. These are Planorbis nathorsti,
P. arcticus, Limnaea vahli, L. holbolli, Succinea groen-
landica, Vitrina angelicae, Conulus fabricii and Pupa hoppii.
The two species of Planorbis are also known from Labrador ;
Succinea groenlandica occurs in Iceland; P. arcticus has
been met with in Scandinavia, Finland and Siberia. The
first of the Limnaeas ranges from Greenland to Alaska,
the other is peculiar to Greenland. The latter, however,
is replaced in boreal North America by the closely-allied
Limnaea retusa. Vitrina angelicae is not found in America,
but occurs in Iceland and Norway. Conulus fabricii is pro-
bably only a variety of the common Conulus fulvus of northern
Europe, Asia and America, while Pupa hoppii is confined to
Greenland. With the single exception of Planorbis arcticus
all these species live at present well within the glaciated area,
that is to say, within that portion of the northern regions
supposed to have been either wholly or partially buried by
ice during the Glacial Epoch. As none but Planorbis arcticus
have ever been found fossil outside that area, we may assume
with some justification that most of them originated in Green-
land, and that all, at any rate, survived the Ice Age in that
country. Planorbis arcticus, as Mr. Kennard § informs me,
has been taken in Pleistocene deposits in Denmark and in
the south of England. (Compare also Kennard and Wood-
ward’s paper.)

It is more difficult to demonstrate that butterflies and moths

* Poppius, B., ‘‘ Coleopteren des Arktischen Gebietes,” p. 428.

+ Strand, E., “‘ Arktische Araneae,” p. 436.

t Mérch, O. A. L., *‘ Land and Freshwater Mollusca of Greenland.”

§ Kennard, A. S., and B. B. Woodward, ‘ Extinct post-pliocene
Mollusca of Southern England,”’ p. 5.

99, ORIGIN OF LIFE IN AMERICA

have survived the Glacial Epoch in Greenland, yet several
authors who have written on the lepidopterous fauna of that
country maintain that the theory of a former land bridga
with Europe and North America is quite consistent with the
facts of distribution. Mr. Petersen,* for example, concludes
from his studies that land connections in high northern lati-
tudes enabled certain arctic butterflies and moths to spread
from a polar centre to Europe and North America. After
alluding to a large number of moths common to Canada and
Europe, Mr. Girard + emphasises the significance of this fact
as indicating the former existence of a land bridge between
North America, Greenland and Europe.

Although no butterflies occur in Iceland, Coleas nastes,
Argynnis chariclea and A. polaris are known even from the
barest and most exposed districts of Greenland, where
nothing but Dryas octopetala and some slender grasses grow.
These species have a wide range in boreal America, Europe
and Asia, but of the nine butterflies known from the arctic
American archipelago five are Kuropean, while only two are
met with in Asia, according to Dr. Pagenstecher. Many
_ striking examples, showing the relationship between Green-
land and the neighbouring continents occur among the moths.
especially among the Noctuidae. Anarta melanopa inhabits
only Colorado, the White Mountains, Labrador, Scandinavia,
Scotland and the Alps. Anarta leucocycla and A. lapponica
are found in Labrador, Greenland and Scandinavia. Mr.
Grote t alludes to no less than twenty-eight other Noctuids
that are common to Europe and North America, even ex-
cluding those met with in Labrador or circumpolar species.
All these facts tell in favour of the view I have endeavoured
to elucidate.

No matter what group of terrestrial invertebrates we
choose, similar close relationships may be discovered between
American and European species, which cannot be explained
by the assumption of a former land connection across Bering

* Petersen, W., ‘‘ Lepidopteren-fauna d. arkt. Gebietes, p. 44.

+ Girard, Maurice, ‘ L’Entomologie de l’Amérique du Nord,”
p. 287.

t Grote, A., ‘Noctuidae of North America,” p. 313.

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POLAR ORIGIN OF LIFE 23

Strait alone. Mr. Emerton* makes mention of several
instances among spiders. _

Such cases can be traced among earth-worms, beetles, wood-
lice, ants and other groups. In some cases the identity or
similarity of species occurring on the two continents may be
due to the fact that the species originated in Greenland or
some polar centre, no longer in existence, and subsequently
travelled in different directions towards their present habitat.
This conception, however, has very little in common with that
of a polar origin of life which was first mooted by Dr. Allen.+
He argued that the northern cireumpolar lands may be looked
upon as the base or centre from which have spread all the
more recently developed forms of mammalian life.

A few years later Dr. Haacke { directed attention to the
peculiar circumstance that the most primitive orders of
mammals and birds all have: their living representatives
in outlying areas of the southern hemisphere, such as
Australia, New Zealand, Madagascar, South Africa and
South America, notwithstanding that these animals are
known to have formerly inhabited the northern hemis-
phere. This, he thinks, implies that a southward re-
treat has taken place of the more ancient forms before
the advancing host of higher orders of life. It -would
seem, therefore, as if streams of more and more highly
specialized orders of mammals and birds had been slowly
evolved in the north and had constantly pressed the older ones
southward. This suggested to Dr. Haacke the idea of a polar
continent from which the various orders had gradually been
distributed across the continents. Dr. Wilser § even assumes
a polar origin for man.

A: similar theory was pronounced by Canon Tristram || in
explanation of the present distribution of the higher groups of
birds and their migrations. The migratory instinct, he con-
tended, was due to their having originated in a polar centre

* Emerton, J. H., “Spiders common to New England and Europe,”
p. 129. 7

+ Allen, J. A., ‘‘Geographical Distribution of Mammals,”’ p. 375.

{ Haacke, W., ‘‘ Nordpol als Schépfungszentrum.”

§ Wilser, L., ‘“‘ Der Nordische Schépfungsherd,” p. 134. .

|| Tristram, H. B., ‘‘ Polar Origin of Life.”

24 ORIGIN OF LIFE IN AMERICA

and having subsequently been dispersed southward by different
routes. He believed that the tendency of birds to migrate
northwards was due to a natural instinct to return to the
home of their ancestors.

What I chiefly endeavoured to prove in this chapter was the
existence in pre-Glacial and early Glacial times of a land
bridge joining Scotland, Iceland, Greenland and Labrador.
The evidence in favour of such a land connection must be
largely, if not entirely, biological ; but the testimony, as far
as it goes, leads me to believe that the theory is well founded.
I shall allude to a similar land connection in another chapter
which probably joined North America and Asia. If the
climatic changes ushered in by the Glacial Epoch were pro-
duced by the closing of these two highways to the Arctic
Ocean, it is evident that the preceding warm period must
have been due to a greater fiow of warm currents to the Arctic
Regions.

A few years ago I drew attention to the fact that the animals
and plants found on the Farées and Iceland in particular
imply the existence of a former land connection between Scot-
land and the latter country. The occurrence in Iceland of the
European field-mouse (Mus sylvaticus), of the snail Arianta
arbustorum, which also inhabits the Fardées, of the beetle
Nebria gyllenhali, which likewise inhabits Greenland, and
many other forms not likely to have been conveyed by acci-
dental means, all favour the view that the fauna of Iceland
owes its existence mainly to the land bridge referred to. But,
as I pointed out, Iceland also possesses a distinctly American
element in the snail Succinea groenlandica and others, while
some of the American plants have even invaded the continent
of Kurope by the Greenland-Iceland land bridge. One of the
objections raised against this view is that the low tempera-
ture in the north would have prevented any faunistie inter-
change across the land bridge. The temperature, on the con-
trary, in Iceland, southern Greenland, Labrador and Scot-
land would have been considerably higher under such geo-
graphical conditions than it is now. ifso, why should not the
whole fauna of northern North America have streamed across
this bridge to Europe and that of northern Europe to North
America ? If we examine the fauna of Canada we find that it

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FAUNISTIC AFFINITIES 25

is largely composed of Siberian immigrants. It is possible that
these only began to enter North America from the extreme
west at the time when Labrador was already joined to Green-
land. Moreover, we may assume that as soon as the North
Atlantic land connection excluded the Gulf Stream from the
Arctic Ocean, glaciers began to gather on all the mountain
ranges surrounding the northern parts of the ocean, thus
preventing many forms of animal life from taking advantage
of the facilities afforded by the land bridge of passing from the
one continent to the other. The greater warmth on the
northern coasts led to greater evaporation of sea water and
more ample condensation of moisture on the elevated lands
surrounding the ocean. All this will be more fully discussed
in the succeeding chapters. |

Apart from the authorities already cited who expressed
themselves in favour of a north Atlantic land connection,
between northern Europe and North America, Professor
Lobley,* Dr. Brown,+ Mr. Grant { and Mr. Krishtafovitch :
have all urged the same view on different grounds. |

* Lobley, J. L., ‘‘ American Fauna and its Origin,” p. 26.

} Brown, A. E., ‘“‘ American Big Game,”’ p. 87.

{ Grant, M., ‘‘ Mammals of North America,” p. 12.

§ Krishtafovitch, N. J., ‘‘La derniére période glaciaire,” p. 296.

CHAPTER II

NORTH EASTERN NORTH AMERICA

Crossine Davis Strait from southern Greenland to
Labrador, we land in a country whose barren headlands look
just as stern and uninviting as those on the opposite side of
the Strait. But whereas the west coast of Greenland pre-
sents a shore-line varying between rugged precipices and
undulating plains, the whole sea-front of Labrador, for over
a thousand miles, rises abruptly from sea-level to a height
of about 1,000 feet or more. Labrador presents‘an irregular
plateau with a general elevation of from 1,500 to 2,000 feet
above sea-level (see Fig. 1). It forms part of the oldest
known land on the continent of North America, and, so far
as we know, it has never been entirely covered by the sea
since very remote geological times. The rocks are largely
metamorphic with ancient igneous intrusions greatly resem-
bling those of Greenland, which, like Labrador, is a fragment
of that ancient continent to which Professor Suess applied
the name “ Laurentia.” *

A cold current of water loaded with icebergs from the
Arctic Ocean sweeps down the east coast of Labrador. Off
the coast of Newfoundland it meets a branch of the Gulf
Stream, thus producing the dense fogs so characteristic of
the Grand Banks. ‘This arctic current is mainly responsible
for the inhospitable nature of the Labrador coast.

The vegetation is mostly stunted in character. The dwarf
birch (Betula nana), the mountain-ash, alder and some
willows here and there form small woods, while many of the ~
familiar Greenland flowers reappear. Yet the flora is dis-
tinctly richer than that of Greenland. Even close to the coast,
in sheltered ravines, occasional specimens of the white spruce,
which is more hardy than the black spruce, are noticeable.

* Suess, E., ‘‘ Antlitz der Erde,” Vol. IIT.2, p. 284.

ANIMALS OF LABRADOR 27

To some of those who landed on the coast and explored the
nooks and valleys, the country seemed full of beauty, of
attractiveness, and even of a rich and appealing fertility. At
certain times it presents an amazing wealth of strikingly
coloured flowers. So thickly sown are they that at certain
seasons they remind one of a cultivated garden.*

Once we leave the coast region and enter the interior of
Labrador, the climate becomes less arctic in character and
timber increases in quantity. In fact there are two distinct
climates in Labrador, the arctic on the coast, the north tem-
perate in the interior.

According to Dr. Packard,+ the Greenland and arctic forms
of animal and plant life occurring on the coast are the
remnants of the glacial or arctic fauna and flora which, being
formerly spread over the entire territory of British America
and the north-eastern United States, still retain their hold
on the treeless and exposed islands and headlands of
Labrador. In many respects the Labrador fauna and flora
resemble those of the far distant White Mountains in New
Hampshire, as we shall learn later on (p. 35).

When we survey the fauna of the coast of Labrador more
closely we find that, besides the Greenland or arctic element,
another much richer one has apparently invaded the territory.
previously occupied by the former. This new fauna becomes
more and more abundant as we proceed westward and south-
ward. Thus the existence of the barren-ground caribou of
Labrador which resembles the reindeer of Greenland, is
threatened by enemies such as the glutton or wolverine (Gulo
luscus), and these do not penetrate farther north. Occa-
sionally the Canadian porcupine (Hrethizon dorsatus) has
been noticed in the coastal territory. Besides the lemming
(Dicrostonyx hudsonius), which is probably identical with
the Greenland form, quite an assembly of distinct ground
rodents make their appearance, among them Synaptomys
innuitus, Microtus enixus, Microtus pennsylvanicus, Evo-
tomys ungava, Evotomys proteus, Zapus hudsonius, and
Peromyscus maniculatus, also the arctic fox, red fox, several

* Grenfell, W. T., ‘‘ Labrador,” pp. 393—395.
+ Packard, A. 8., ‘‘ The Labrador Coast,” p. 194.

28 ORIGIN OF LIFE IN AMERICA

small carnivores and a variety of the black bear (Ursus
americanus) .*

The small mouse-like creatures belonging to the genus
Synaptomys are aptly called “ lemming-voles ” because, ex-
ternally like lemmings, their teeth approach those of voles.
When Dr. Merriam undertook his revision of the species of
Synaptomys,}+ seven kinds were known to him. A few more
have since been discovered. The genus is entirely confined to
the North American continent, and all the species except two
have a limited range in the boreal region. One of the latter
(Synaptomys cooperi) is found from Massachusetts westward
to Minnesota and southward to North Carolina, the other is
peculiar to Mount Washington. Almost all the other species
are confined to Canada and Alaska. It does not seem, there-
fore, as if Synaptomys innuitus, which inhabits the coast of |
Labrador, were a recent immigrant from the south. On the
contrary, the genus Synaptomys, being almost confined to the
north, is probably of boreal American origin, one adaptable
species having advanced far southward along the east coast
of America.

The next two species alluded to, Microtus enixus and M.
pennsylvanicus, are true voles, though the last-named animal
is generally known in the States by the name of ‘“ meadow-
mouse.” Both of them belong to a sub-genus which is
very widely spread in Europe, Asia and boreal North
America.{ Some migrations across ancient land connections
must have taken place, no matter whether we assume that the
sub-genus is of Old World or New World origin. It only
remains for us to determine whether Microtus crossed the
North Atlantic land bridge or the one supposed to have been
situated at Bering Strait, assuming that there was such a one.
Professor Tullberg thought the members of the genus Microtus
had travelled to America in Pliocene times by means of the
first land bridge.§ This view does not appear to me pro-
bable, because the family is entirely absent from Ireland,

* Bangs, O., ‘‘ Mammals of Labrador.”

+ Merriam, C. H., ‘‘ Revision of Synaptomys.”

t Bailey, V., ‘‘ Revision of Microtus.”’

§ Tullberg, Tycho, ‘‘System der Nagetiere,” p. 499.

VOLES AND JUMPING-MICE 29

Iceland and Greenland. There is no fossil evidence that voles
ever lived in any of these countries, where we might expect
them to have survived had any extensive migration taken place
from Great Britain to North America. Neither in Hurope nor
in North America are there any fossil remains of the sub-
genus Microtus older than Pleistocene, if we accept Mr.
Barnum Brown’s estimate of the age of the Potter Creek
deposits.* Nevertheless, it is possible that these voles origi-
nated in North America long prior to the Pleistocene Period.
If so I believe they made use of the Bering Strait land con-
nection rather than the North Atlantic one, in passing from
the New World to the Old.

Evotomys, another genus found in the coastal district of
Labrador, has a range somewhat similar to that of Microtus.
It is closely allied to it and scarcely deserves the name of
“red-backed mouse ” as the Americans call it, because it is
distinctly a vole, without any mouse-like characters about it.
The relationship between the American and Old World forms,
as in the case of Microtus, must be due to the existence of a
former land bridge across Bering Strait.

The jumping-mice (Zapus), to which Zapus hudsonius
belongs, are, in many respects, an interesting group of
rodents. Somewhat kangaroo-like in their movements, they
are almost entirely confined to boreal North America. The
Labrador jumping-mouse is a variety of Zapus hudsonius,
which ranges from Alaska to Labrador and New York. A
single species of jumping-mouse (Zapus setchuanus) occurs in
China.} The theory that a former land bridge across Bering
Strait enabled its ancestors to traverse the northern Pacific
seems quite evident in this case. Yet we must not forget that
the American jumping-mice also have somewhat more dis-
tant relations in the Old World, the jerboas, from which the
remote ancestors of Zapus may possibly have descended.

We need not at present deal with the other rodents or the
carnivores found in the coast district of Labrador, as most of
these will be referred to again in subsequent chapters. The
animals that have just been alluded to show us that the

* Brown, Barnum, “ Conard fissure,” p. 208.
t+ Preble, E. A., ‘‘ Revision of the Jumping Mice.”

30 ORIGIN OF LIFE IN AMERICA

Labrador fauna is largely composed of indigenous American
species, which have not penetrated to Greenland. This seems
to suggest that the points of resemblance in the fauna of
Labrador and Greenland may have been more marked in
remoter times, before the influence of the continental fauna
had impressed itself upon the outlying peninsula of Labrador.
Considering the extreme probability of Labrador having been
connected by land with Europe by way of Greenland and
Iceland in Pliocene times, we might expect some Euro-
pean mammalian types to have occurred in north-eastern
North America. The little evidence we possess tends to
show that the mammalian life of the extreme north of
western Europe was always poor. We cannot assume
that insurmountable barriers prevented European mammals
from invading America, because certain species such as the
reindeer and lemming seem to have passed from America to
Europe across a North Atlantic land bridge. It might be
argued that Huropean animals did cross over, but were unable
to maintain themselves in America, a fate which has largely
befallen the American immigrants in Europe. For such a
supposition, however, we still lack evidence. If no examples
of European animals or plants were known from the American
side of the water, we might assume the land bridge to have
been a discontinuous one, as Mr. Hedley suggested to me,
connecting Greenland alternately with Labrador and Scotland.
‘But one of our strongest supports for the North Atlantic
land bridge is, as I said, the presence of the Huropean
Helix hortensis in North America. It still occurs in
Labrador. From Labrador it travelled southward along the
coast. Is it possible that the whole strip of coast was at
that time cut off by some barrier from the interior of
North America ?

Supposing the western parts of the Labrador plateau had
become covered by glaciers as soon as the North Atlantic land
bridge was formed, it might have produced an effectual barrier
against western invaders and yet have allowed eastern forms
to reach Labrador.

Later on I intend to return to this problem again. Mean-
while, let us journey westward across the high plateau of
Labrador towards Hudson Bay and Central Canada. As we

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NORTHERN FROGS S31

enter the vast forest region, plant life as well as animal life
become more and more abundant and differentiated. ‘In-
stead of the barren-ground caribou, we now meet with the
woodland form accompanied by another large ungulate, the
moose, while the flying squirrel, chipmunk, the ground
Bquirrel, woodchuck, white-footed mouse, musk-rat, beaver,
skunk, weasel, shrews, moles and many other beasts tenant
the forests, meadows: and banks of rivers.*

A few amphibians, even, have succeeded in surviving the
rigours of the arctic winter of those regions, and have success-
fully established the most northern outposts in eastern North
America. The leopard frog (Rana pipiens), one of the
commonest as well as one of the most brilliantly coloured of
American frogs, is one of these. The pickerel (Rana palus-
tris), also the northern wood frog (Rana cantabrigiensis)
and the northern frog (Rana septentrionalis) have all been
observed in the neighbourhood of Hudson Bay. The most
interesting species is the swamp-tree frog (Chorophilus
nigritus), whose northern variety has advanced into this in-
hospitable region, though almost all of the other members
of the tree frog family (Hylidae) are typically southern
forms. Whether newts occur in the Hudson Bay region is
not definitely known, but the salamander (Plethodon
cinereus), at any rate seems to have been met with. All these
species are peculiar to America.

No reptiles have been noticed. The distribution of the
terrestrial mollusks, the snails and slugs, implies that an ad-
vance in a northward direction, similar to that recorded in
the case of mammals and amphibians, has taken place among
some groups of invertebrates. The typically American snails,
Polygyra monodon and Strobilops labyrinthica, have been
collected near Hudson Bay.

When we analyse the constitution of all these western and
_ southern groups, and trace the relationship of the members

' more carefully, we notice that many of them are not of

_ American ancestry. They all have lived, no doubt, long
| enough in America to have become thoroughly established,

* Preble, E. A., ‘‘ Hudson Bay Region.”
+ Dickerson, Mary ©., ‘‘ The Frog Book,” p. 158.

32 ORIGIN OF LIFE IN AMERICA

being part of the indigenous fauna, yet we recognise that their
ancestors must have entered the continent from Asia in com-
paratively recent geological times.

Let us take for example the moose deer (Alces americanus).
Its range extends from, Bering Strait, in a broad tract of forest
land eastward, along the northern shores of the Great Lakes
as far as Nova Scotia on the Gulf of St. Lawrence. Only
along the Rocky Mountains, as Mr. Thompson Seton has so
clearly indicated in his map of the range (Fig. 3), does the
moose occur further south.*

There are a few historical records, and also some fossil
ones, which indicate that the moose once penetrated further
into the United States in various directions, but it evidently
never diverged very much from its present range.t ‘The bones
of a couple of closely allied animals have been met with in the
Pleistocene deposits of Washington territory, and the skeleton
of a peculiar moose, somewhat resembling the Alaskan variety,
has been discovered in the Pleistocene of New Jersey, and
placed by Professor Scott into a distinct genus (Cervalces).
- Whether this animal was ancestral to the living moose, as
has been suggested, or whether it represents an aberrant
type which has come in from Siberia with the moose, as Mr.
Grant seems to think likely, are problems which may be
left to future researches.{ Certain it is that when we cross.
Bering Strait into Northern Asia, we meet with a moose
(Alces bedfordiae) which in its simple antlers somewhat
resembles the young American moose. Further west as far as
Scandinavia, we find another species (A. machlis) differing
but slightly from Alces americanus. It seems almost as if
the moose had originated in eastern Asia from some more
generalised type like Alces bedfordiae, and had gradually
produced the forms with more palmated antlers in America
and Europe by a process of convergent evolution. In any
case, we are led to assume that Bering Strait was dry land
when the ancestors of the existing moose entered the New
World. Even if we suppose the moose to have originated in
America, a land bridge connecting the latter with Asia was a

* Seton, Thompson, “ Life Histories of Northern Animals, I.,” p. 151.

+ Grant, Madison, ‘‘ Moose.”’
t Grant, Madison, ‘“ Origin and Relation of Mammals,” p. 23.

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MOOSE DEER 83

- necessity. This problem of the Bering Strait land bridge,
_ however, will be more fully discussed later on (pp. 883—86).
_ The moose, or elk as it is called in Europe, has been stated
to occur in the Caucasus, but its range only extends to the
_ forests north of this mountain range. Like the reindeer, it.
occurred much further south formerly, even as far as
_ northern Italy, and yet no theories as to a former arctic
climate are founded on this fact. In Caesar’s time the elk was
still abundant in the Black Forest in southern Germany,
while it is now confined to certain parts of Russia and
- Scandinavia.
Many other American species resemble the moose in their
_ range, except that they manifest more clearly their Asiatic
origin. The further west we travel the more often do we
_ meet with such types of animals.
te We have now become acquainted with species that seem
to be of arctic American or Greenland origin. A few
_ apparently travelled across from Kurope. Others were partly
_ of southern extraction having advanced northward from the
_ United States, and partly derived from a western invasion of
_ the continent. What we want to find out next is the geological
' age of some of these invasions into boreal America. The
_ writings on this subject of the prominent biological authors
| are largely biassed by the prevalent geological opinions with
' regard to the nature of the Ice Age.

It is currently believed that a climatic change towards the
end of the Pliocene Period caused ice-masses to form in
various Canadian centres, so as to produce continental
_ glaciers of the type of the ice-sheet now covering Greenland.
“ These glaciers are supposed to have spread from at least three
_ centres in Canada, termed the Labradorean, Keewatin, and
' Cordilleran. During this time, viz., in our most recent
| geological age, the ‘‘ Pleistocene Period,” fully one half of
_ North America is thus assumed to have been gradually buried
_ beneath these vast sheets of ice. Ice is believed to have ex-
) tended practically all over the continent from Newfoundland
' in the east to Vancouver in the west, and from the Arctic
_ Ocean to the present site of the City of St. Louis.* Relying

* Russell, I. C.,.‘* North America,” p. 315.
L.A. D

834 ORIGIN OF LIFE IN AMERICA

on the accuracy of these data, on which the majority of
geologists are agreed, biologists have endeavoured to work
out the past history of the American fauna in strict accord-
ance with the facts these phenomena are thought to reveal.
“Throughout the growth of the great ice-mass, and its ex-
tension from the north southward,” says Dr. Merriam, “ it
is clear that the animals and plants that could not keep pace
with its advance must have perished, while the steady push-
ing towards the tropics of those that were able to escape to
the rapidly narrowing land in that direction must have
resulted in an overcrowding of the space available for their
needs and a corresponding increase in the severity of the
struggle for existence.’’** Immediately upon the close of the
Glacial Epoch life began to reclaim the regions from which
he thinks it had so long been shut out.

Dr. Allen’s views are very similar. “‘ There is evidence,”
he remarks, “‘ that towards the close of the Tertiary, a marked
change in the earth’s climate took place, culminating in the
Glacial Period, during which the whole northern half of the
northern hemisphere became covered with a heavy ice-cap,
lasting for possibly thousands of centuries, and extending
its chilling influence nearly to the northern tropic. The rise
of the Glacial Period was of course gradual, and the south-
ward progress of the great ice-cap drove before it all forms
of life capable of any considerable powers of locomotion, while
those unable thus to escape must have perished from cold.
Finally the ice receded to its present limits and the whole
north, under radically altered climatic conditions, became
again available for occupation by the more or less modified
descendants of. the pre-Glacial exiles.’’+

The bog plant societies so graphically described by Mr.
Transeau probably existed, he thinks, along the whole ice
front. The bog and tundra types were eventually the first
to push into the barren ground left by the retreating ice.

Professor Adams takes a more independent attitude. He
assumes that repeated glaciation had almost sterilised the

* Merriam, C. H., ‘‘ Life in North America,” p. 45.
t Allen, J. A., ‘‘ Distribution of North American Birds,”’ p. 100.
{ Transeau, EH, N., ‘‘ Distribution of Bog Plant Societies,” p. 414.

FAUNA OF WHITE MOUNTAINS 35

northern part of the continent, still he concedes that even
during the Glacial Epoch, life of the tundra type may have
flourished in Alaska.*

Hence it is not unreasonable eo argue from his point of
view that life could also have existed in Greenland at that
time, and this opinion I endeavoured to vindicate in the
last chapter. Even Professor Adams does not venture to
cast a doubt upon the correctness of the current geological
theories, and speaks of three distinct belts of life in the
vicinity of the ice margin (p. 56). The latter being fringed
to the south by tundral biota (fauna and flora), next to which
came the northern trans-continental coniferous forest belt
and its associated fauna, and finally the deciduous forests.
All these are assumed to have moved forward to the north on
the disappearance of the ice.

That the so-called ‘‘ tundral ” or what we might call arctic
fauna and flora actually did advance far south of their present
habitats can be demonstrated much more clearly than by the
occurrence of a few stray fossil reindeer’s antlers south of
the area. covered by glacial drift.

Whether the past southward migrations of the reindeer
were influenced by climatic changes or by other considera-
tions, we cannot definitely assert. Since we are told that
there was a refrigeration of the climate during the Glacial
Epoch, we are apt to assume that this lowering of the tem-
perature drove the reindeer and other arctic species to more
southern localities. The former occurrence of an animal of
such a roving disposition as the reindeer in more southern
districts may have been due to a natural expansion of its
range, and this need not imply a change of temperature.

The fauna and flora of the White Mountains has been cited
as a living testimony of a former arctic climate in latitudes
where temperate conditions now prevail.

Surrounded by an entirely alien assemblage of animals and
plants we find in the White Mountains of New Hampshire,
not far from the city of Boston, an extraordinary gathering
of species, many of which are only known elsewhere in
Labrador and Greenland. A thousand miles away from their

* Adams, Chas. C., ‘‘ Dispersal of North American Biota,’’«pp. 55—48,
D 2

36 ORIGIN OF LIFE IN AMERICA

natural home, they form in the White Mountains a peculiar
island colony on a bare plateau which lies about 5,000 feet
above sea-level, and out of which project a series of conical
peaks. These constitute what is known as the Presidential
Range, the highest being Mount Washington (6,293 feet)
(Fig. 4). The plateau on which this remarkable relict fauna
and flora lives may be reached by the railroad that now takes
the traveller to the top of Mount Washington or by following a
very rough trail leading to it from the Pass called ‘‘ Crawford’s
Notch ” through the dense forest. It was the latter route I
chose to gain the wind-swept ridge. As we approach the
ridge, the fine spruce, balsam and paper birches are gradually
replaced by diversified conifers, which become increasingly
stunted by exposure in the more elevated parts of the range.
At last, on emerging from the remnants of the forest, we
have gained not only a wide expanse of open country, but we
can imagine ourselves transplanted all of a sudden to the
Arctic Regions. Here and there may be gathered specimens
of Rhododendron lapponicum and Salix phylicifolia, growing
among Arenaria groenlandica, Phleum alpinum, Diapensia
lapponica, Campanula rotundifolia, Gentiana nivalis and
hosts of others, few of which can be badied elsewhere nearer
than Labrador.

Moreover, as Dr. Scudder remarked, no State in the Union
presents so striking an assemblage of animal life as New
Hampshire, where the White Mountains form so conspicuous
a feature. Swiftly running over the bare rocks of the high
plateau we notice the black spider, Pardosa groenlandica,
which, though occurring also in the Rocky Mountains, .is
otherwise confined to the White Mountains, Labrador and
Greenland.* The grasshopper, Pezzotettix glacialis, is, I
believe, peculiar to Mount Washington, while another species,
Pezzotettix borealis, is a near relative of the North Kuropean
Pezzotettix frigida. Fluttering among the arctic vegetation,
we notice the butterfly Oeneis semidea, which has never been
taken nearer than Labrador, while the moths Dasychira rossii,
Arctia quenselii and Anarta melanopa, are all well-known

* Chamberlin, R. V., “ Revision of North American Lycosidae,”’
p- 200.

_

wall

Ba
——acoemec em |
_— JZ, sa
oS ee
NG cn 0
==) ;
= | oy,
re) Ss
= =
— -:
—— . * 4s
Be:
ec ' L
+ Cm! |
ah tL
=——e ¢ ‘

Fig. 4.—Map showing the outlines of the Whité Mountain Plateau (shaded) and
Mount Washington Range (black), with an inset Map of North America,
indicating the position of the White Mountains (in the centre of small circle).

[ To face p. 36.

ORIGIN OF WHITE MOUNTAIN FAUNA 37

arctic species occurring on the White Mountain plateau.*
Among the beetles, too, and other groups of invertebrates,
there are many arctic forms, showing clearly the intimate
relationship that exists between the faunas of the White
Mountains and Labrador.+

Even among mammals we have some most interesting
boreal representatives, the White Mountain lemming-vole
(Synaptomys sphagnicola) being peculiar to this region.{ In
alluding to the mammalian fauna of Labrador I specially
dealt with this genus, and expressed the belief in its arctic
origin and subsequent southward dispersal (p. 28).

If merely a few arctic plants and insects inhabited this re-
markable plateau, the argument might be permissible that
they had been carried southward by wind currents from their
northern home at great intervals of time and had successfully
established themselves in this manner on the White Moun-
tains, because the latter proved to be uninhabitable by the
fauna and flora of the surrounding country. No one, however,
who has seriously studied this congregation of animals and
plants as a whole, can for a moment entertain such an idea.
We must therefore take for granted that a fauna and flora
similar to that now existing in Greenland, Labrador and on
the White Mountains once extended over a large portion of
Canada and at any rate the north-eastern United States. The
problem to be solved is, what were the circumstances which
led those animals and plants to extend their range so much
southwards? The prevalent theories regarding these move-
ments have already been referred to. They are simple enough.
Similar ones have been current in Hurope for many years
past. I shall quote Professor Adams§ again, as his views
seem to me to express those generally entertained on
this subject. After an allusion to the final northward retreat
of the ice which he supposed to have crept down from the
north “grinding to pieces everything beneath its awful

* Scudder, 8. H., “ Distribution of Insects in New Hampshire,”
pp. 331—341.

t+ Gardiner, F., ‘‘ Coleoptera of the White Mountains.”

¢ Miller, G., ‘‘ Mammals of New Hampshire Mountains.”

§ Adams, Charles C., ‘‘ Post-glacial Origin of the life of North-
Eastern United States,” p. 309.

38 ORIGIN OF LIFE IN AMERICA

weight,”’ if once more permitted life from the south to move
into the newly opened territory. The first wave of life, he
thinks, which became dispersed over the glaciated region, as I
have already mentioned above, was the barren-ground fauna
and flora, the types of the far north. ‘“ Hardly a trace,”
he continues, “ now remains in the eastern United States of
this pioneer class, and this class is now restricted to very
limited areas or mountain top ‘islands,’ as in the White
Mountains. The present distribution of these arctic-alpine
‘islands’ brings up a number of very interesting points. How
is it that these alpine plants and animals are now found so far
south and only upon high mountain peaks? This question
could not be rationally explained until the influence of the Ice
Age upon life became recognised, and would, indeed, be a
difficult one to answer if we did not take into consideration
past conditions of climate and topography. We must recall
that the arctic conditions which now occur outside of the arctic
regions only on high mountain tops at that time extended to
the very base of the mountains, and as the ice retreated to the
north this cold zone gradually moved up the sides of the
mountains carrying with it a characteristic flora and fauna.
Thus with the retreat of the ice the first wave of life had
two evident possibilities before it: first, to follow the ice
north, or to follow the cold zone up the mountains. By this
means small colonies of arctic plants and animals became
separated from the main body of forms, and thus became
alpine. To be sure, this segregation could only occur where
the mountain peaks are isolated. If the mountains had been
of sufficient height and had extended far to the north, a high-
way would have been retained to the original stock, and thus
the distribution would not have become discontinuous. From
the above interpretation it seems fair to conclude that the
arctic forms which now occur at alpine heights are relicts of
the former widespread glacial fauna and flora, whose dis-
tribution has become discontinuous by a change of climate.”

Very similar ideas were held by Mr. Grote.* He thought
the White Mountain butterfly (Oeneis semidea) was pushed
southwards by the advance of the great northern ice-sheet.

* Grote, A. R., ‘‘ Effect of Glacial Epoch,” p. 441.

ORIGIN OF WHITE MOUNTAIN FAUNA 39

On the decline of the ice-sheet the butterflies turned north-
ward, again returning to their native home. Some of the
specimens strayed by the way and were destined to plan”
_ colonies apart from their companions as, for example, on the
White Mountains. |

Botanists entertain analogous views. Dr. Harshberger *
argues that the tundra vegetation and other arctic species
of plants occupied during the Glacial Epoch the southern
margin of the great ice-sheet, and that when most of them
migrated north, on the disappearance of the ice, some re-
mained behind to form the vegetation of sphagnum bogs and
alpine summits of the higher mountains.

If these theories are correct, the Asiatic invasion and the
much more insignificant one from Hurope, of which Helix
hortensis is one of the most striking representatives (p. 13),
should both be more recent than the flora and fauna of the
White Mountains, for the former have not penetrated beyond
the lower slopes of these mountains.

Helix hortensis does not occcur nearer the White Mountains
than Portland in Maine, which is fully seventy miles to the
east. I have traced Oniscus asellus, a wood-louse probably
belonging to the same group, as far as the base of the White
Mountains. The earth-worm, Lumbricus castaneus, which
seems to have spread from ‘continental Europe to the Farées
and Iceland, reappearing on the other side of the Atlantic
in Canada and New England, may be a member of the same
dispersal. At any rate, I feel sure there are a great many
more of such species that have not spread to the higher parts
of the White Mountains, and therefore proclaim themselves as
more recent immigrants than those which are now in posses-
sion of the high plateau referred to. The latter are likewise
clearly older than the Asiatic immigrants, which will be more
fully deseribed later on.

But since Helix hortensis occurs in the lower Pleistocene
clays of Maine, it, as well as the whole group of European
immigrants, are pre-Glacial in age, and in this opinion I
concur with several of the authorities who have discussed,
this problem (p. 14). The members of this group arrived

* Harshberger, John W., ‘‘ North American Plant Dispersal,’’ p. 2..

40 ORIGIN OF LIFE IN AMERICA

in America before the time when the glacial drift was de-
posited, or, in other words, when the northern ice-sheets were
‘supposed to have advanced to their southern limits. The
glacial drift, I may mention again, is the mantle of clay, sand
and boulders believed to have been left by the ice as it
retreated northward. ‘Whether this drift or boulder clay really
is the product of immense glaciers, or whether it was deposited
in the sea by floating icebergs, it is evident that wherever the
country is covered by it the pre-existing fauna and flora must
have been destroyed. The evidence seems to me all in
favour of destruction rather than emigration.

The idea of a gradual southward withdrawal of the fauna
and flora, that they fled like a conquered army before an ad-
vancing foe, sounds very plausible, but is there any foundation
for such a belief ?

No evidence can be adduced from fossil specimens that
any members of what I have called the Huropean invasion
ever penetrated southward of the limits of the drift in North
America. They do not seem to have been pushed south in front
of the advancing masses of northern ice. Theoretically, they
ought to have survived the Ice Age somewhere in south-eastern
North America. If they did, they must subsequently have
reoceupied the very parts, viz., Labrador, Newfoundland and
the coast of New England, where they originally set foot
on American soil after completing their travels across the
North Atlantic land bridge. But is it possible that they
quitted the south-eastern States without leaving a trace of
their former presence there ? As Dr. Harshberger * points
out, not a single species of thirty-four plants characteristic
of the area just south of the glacial drift deposits, is a native
of Europe. On the other hand, of the plants growing on
the drift itself, about one-third are common to northern
Europe and America. All the available evidence, therefore,
points to a survival of the Huropean element within the
glaciated area.

Could any islands have existed in the midst of this glaciated
area, where this assemblage of European plants and animals

* Harshberger, J. W., ‘“‘ Comparative Age of Floristic Elements,”
De 606.

i
4
¥

NORTH-EASTERN RELICT COLONIES 41

might have survived the Ice Age, without being affected by
the Ice-sheets ? 3

Labrador was one of the areas which was believed to have
had an independent centre of glaciation, yet Professor Daly,*
after making a special study of the geology of Labrador,
remarked ‘“ nothing is more striking in the glacial geology of
the southern part of the coastal belt than the almost com-
plete absence of drift deposits.” In the Torngat Mountains of
Labrador no signs of glaciation were noticeable above 2,000
feet. That there were considerable tracts of Labrador which
were free from ice must be evident, and I presume the Euro-
pean plant and animal migrants survived the Glacial Epoch

there and also further south. The island of Newfoundland

seems to have had quite a separate area of glaciation, and the
same was probably true of Nova Scotia, according to Pro-
fessors Chamberlin and Salisbury.+

The two countries of Labrador and Newfoundland have
many species of animals and plants in common, and in both
no doubt a large part of the pre-existing fauna and flora sur-
vived the Glacial Epoch. I have urged in the last chapter
(p. 14) that the land probably stood at a much higher level
towards the beginning of the Pleistocene Period than at pre-
sent, the whole of the Bank of Newfoundland, and southward
as far as Cape Cod, being raised high above sea-level. While
I claim that the remainder of boreal North America has sub-
sequently become largely submerged, these eastern tracts are
likely to have remained above water, thus forming an asylum
for the survival of the arctic and Old World fauna and flora.
This opinion is confirmed by Professor Upham’s { remark
that the elevation of the fossiliferous marine beds lying on the
glacial drift increases as we proceed north-westward from
Boston, that is to say, inland, while along the lower St.
Lawrence it decreases again, so that in Nova Scotia actually
on the sea-coast marine deposits are wanting.

The current geological theories of the Ice Age or Glacial

* Daly, R. A., ‘‘ Geology of Labrador,” pp. 245—251.

t+ Chamberlin, T. C., and R. D. Salisbury, ‘“ Geology,’ Vol. III,
p. 336.

t{ Upham, Warren, ‘“ Marine Shells near Boston,” p. 140.

42 ORIGIN OF LIFE IN AMERICA

Epoch do not seem to me to harmonise at all with the geo-
graphical distribution of animals and plants. If we assume
that an arctic climate prevailed at that time all over Canada
and the northern United States, we are faced by numerous
difficulties. The biological evidence favours the view that the
climate in boreal North America, though much more humid
than at present, so that it led to extensive glaciation on all
higher mountain ranges, was not arctic but temperate, and
that in many parts within the so-called glaciated area there
existed islands where life was abundant and survived to the
present day.

Let us return to the animals and plants inhabiting the
White Mountains. Their relationship is almost altogether
with Lapland and Greenland, and yet that affinity has clearly
been brought about at a much earlier date than that of the
arrival of the Kuropean element in North America.

During the Pliocene Period movements seem to have taken
place resulting in an increased height of land. This need not
necessarily have affected the whole of North America. It was
probably more or less confined to the north-eastern and north-
western parts. While the closing of the North Atlantic left
the coastal districts open to the beneficial influence of the
Gulf Stream, the temperate fauna and flora must have gradu-
ally disappeared from the more inland boreal parts of the con-
tinent, thus leaving room for the expansion of the arctic
animals and plants in various directions. It was during the
Pliocene Period, I think, or earlier, and, at any rate, long
before the commencement of the Glacial Epoch, that the
animals and plants from Labrador thus found their way south-
ward to the White Mountains. However, | shall bring forward
further evidence later on which will throw additional light
on the problems I have discussed.

The theory that the animals and plants were driven south
of the ice foot or southern margin of the supposed great
ice-sheet ought to be supported by biological evidence.

Theoretically it is assumed that the barren-ground or arctic
fauna and flora lived close to this margin, as already stated,
and the temperate forms further south. The only fossil evi-
dences we possess of arctic animals having actually lived south
of the ice-sheet, or, as we might say, south of the limits of

EFFECTS OF ICE AGE ON FAUNA 43

_ the drift, are rather problematical. Most, if not all, the occur-
_ rences of reindeer and musk ox bones lie within the drift area.
_As already mentioned, animal remains have been met with in
caves and other deposits, close to the limits of the drift, and
supposed to belong to the Pleistocene Period, which seem to
indicate a climate somewhat milder than the present one.

- The most noted Pleistocene fossiliferous strata within the
drift area lie in Canada, and these contain largely the remains

' of plants. Since the first place as tests of climate has gene-
| rally been assigned to plants,* their testimony will be of
| particular value in our present enquiries. These deposits have

_ been principally studied by Professors Coleman + and Pen-

| hallow.{ Some are in the neighbourhood of Toronto near the
} shores of Lake Ontario, others further west near the Moose

| and Albany Rivers, both of which empty their waters into
| Hudson Bay.

| In dealing with the beds in the neighbourhood of Toronto,
| Professor Coleman reports that those of Searboro’ Heights
contain mosses, diatoms, a few fresh-water shells and a con-

| ' siderable number of elytra of beetles. According to Dr.
| Scudder the latter, numbering twenty-nine species, are all
| extinct, and related to species occurring in Lake Superior and

Hudson Bay regions, the fauna having a boreal aspect. The

| fossils from the Don River deposits were found to be sur-

| prisingly different. They seemed to point to a climate as

| warm as that of Toronto, if not much warmer, while the forest
| trees suggest a temperature far from glacial. Not a trace of
! - an arctic fauna or flora could be discovered. It was con-
| cluded, therefore, by Professor Coleman that both these series
| of beds were inter-glacial, that is to say, laid down during the
| mild phases which are supposed to have separated the in-
| tensely arctic ones from one another.

| ‘The plant remains from the other deposits were like those
| of Scarboro’ Heights and Montreal. They were essentially of
the same character representing a vegetation similar to that

_ of our own time, or perhaps even a little more severe.

| q _* Seward, A. C., ‘‘ Fossil Plants as Tests of Climate,” p. 10.
| ~— t¢ Coleman, A. P., “Glacial and Inter-glacial Deposits,”’ pp. 625—640.
t Penhallow, D. P., ‘‘ Pleistocene Flora of Canada,” p. 77.

t4 ORIGIN OF LIFE IN AMERICA

Four years later a valuable report on the Pleistocene fauna © )

and flora of Canada was read at the British Association Meet-
ing at Bradford by a committee which had been appointed to
investigate the subject. Of this committee, Professor Cole-
man and Professor Penhallow were members, as well as
Sir William Dawson.* The number of beetles brought to light
from the Scarboro’ Heights had now increased to seventy-two
species, of which seventy were pronounced by Dr. Scudder to

be extinct. The new species confirmed Dr. Scudder in the q

opinion, previously expressed, that on the whole the fauna
has a boreal aspect, though by no means so decidedly boreal
as one would anticipate.

No less than eighty-three species of plants were studied
from eighteen different localities, one of the plants, viz., Acer
pleistocenicum, being extinct. The abundant occurrence of
some species, such as the Osage orange (Maclura aurantiaca),
the paw-paw (Asimina triloba) and others, point to the pre-
valence of a much warmer climate than now prevails. On
the other hand, the equally abundant occurrence of boreal
types at Scarboro’ Heights suggests the existence of a cooler
climate at the time these deposits were laid down.

Once more, in 1907, Professor Penhallow + dwelt upon the
results of his researches on the plant remains of the Don
River beds, urging that the same flora must have characterised
the entiré region between Virginia and Ontario in Pleistocene
times, whilst a much warmer climate than at present pre-
vailed.

If similar evidence were brought to light from any other
deposit than the Pleistocene, there can be no doubt as to the
conclusions that would be drawn from it. The climate in
boreal North America during the Pleistocene Period, as re-
vealed by the plant and animal remains, must have been on the
whole a temperate one. Yet geologists maintain, in the face
of this testimony, that all these plant and animal remains only
represent the so-called interglacial phase of the Glacial
Epoch, during which the climate was supposed to have been
temperate or mild. The other phase of the Ice Age, they

* Dawson, J. W., D. P. Penhallow and others, ‘‘ Canadian Pleistocene

Fauna and Flora,” p. 334—338.
+ Penhallow, D. P., ‘‘ Pleistocene Flora of Canada,” pp. 443—450.

ed * . a > - aq
a ae ee ee ee - =e

ee ee ee

a a ote

ON INTERGLACIAL EPOCHS 45

argue, has left no traces of animal or plant life in all the
numerous deposits which have been examined.

_ The whole conception of these interglacial phases of the
' Glacial Epoch has given rise to a good deal of animated
discussion. Professors Chamberlin and Salisbury have
adopted Professor James Geikie’s view that there were
six great advances and retreats of the ice-sheets, sepa-
rated by five interglacial intervals, during which a mild
climate prevailed. But the evidences for these alternate
_ advances and retreats of the glaciers are by no means ad-
' mitted as valid by all geologists. Some maintain that there
_ were only three such great advances and retreats. Others
| admit only two of them. Some authorities disbelieve alto-
' gether in mild interglacial phases, and admit only one ad-
_ vance followed by a gradual retreat of the ice. Even after |
_ studying the Toronto clays, which Mr. Lamplugh * acknow-
_ ledges impressed him strongly as affording the kind of evi-
_ dence which he has sought in vain in Britain, he is still of
_ opinion, as expressed in his address to the Geological Section
_ of the British Association, that there is no proof of mild inter-
_ glacial epochs, nor even of one such epoch.

_ My own conclusions as to the nature of the Glacial Epoch,
' and the causes that produced the glacial clays, being almost
entirely based on the evidence derived from the past and pre-
' sent fauna and flora, I have no hesitation in agreeing with
_ Mr. Lamplugh’s views. There is no biological evidence in
_ North America in favour of one or more interglacial phases.
_ Everything moreover points to the fact that during the so-
- called Glacial Epoch there was no diminution of temperature,
| or if so only a very partial one, although the higher mountain |
| ranges were covered by glaciers. In many parts of North
| America there was probably a higher temperature during the
| Ice Age than obtains at present. The first to advocate the
| idea of a higher mean temperature being compatible with a
| greater extension of glaciers was, I think, Professor Lecog.+
~ Mauch more recently a similar theory was very ably main-

| ™* Lamplugh, G. W., “On British Drifts and the Inter-Glacial Problem,”
p. 26.
| + Lecoq, H., “ Des Glaciers et des Climats.”

46 ORIGIN OF LIFE IN AMERICA

tained by Professor Whitney.* and was supported by weighty
arguments, while Sir Henry Howorth + has contributed addi-
tional testimony in favour of a mild climate having prevailed.
during the so-called Glacial Epoch or Ice Age. .

That extensive glaciers existed during that Epoch in
western Europe and north-eastern North America is pri-
marily due to the closing of the North Atlantic. This pro-
duced a rise of temperature in the Atlantic Ocean and intense
precipitation over western Europe, particularly Scandinavia,
and also over north-eastern America, especially Labrador.
As Professor Whitney observes, the regions mentioned are the
only two in the world in which the topographical and climatic

conditions seem to have been considerably different during the ~

Glacial Epoch from what they are at present. The prevail-
ing opinion, however, among geologists is, that not only was ~
there a centre of glaciation in Labrador, but also in the
Keewatin district to the west of Hudson Bay. The latter being —
a perfectly flat region, without even a suggestion of a moun- —
tainous nucleus, constitutes,indeed, as Professors Chamberlin ~
and Salisbury { acknowledge, one of the most marvellous fea- —~
tures in ice dispersion. All our notions as fo the behaviour of ~
glaciers are derived from careful observations on existing ones. ©
But nowhere on earth can a glacier be seen which, having
originated on level land and developed quite independently of —
any adjacent higher region, proceeds to invade the neigh- —
bouring areas. Hence a biologist may be excused for express-
ing some hesitation in accepting so extraordinary an hypo-
thesis in spite of the fact that we are assured that the days —
of reasonable doubt as to the former existence of these almost —
inconceivably large ice-fields are past.

To attempt even to discuss all the various lines of evi-
dence which have led to the almost general acceptance of the
land-ice theory, as understood at the present day, would be —
impossible in a work of this nature. I only wish to bring —

forward some of the chief reasons which have prevailed upon —

me to reject this theory. I can scarcely venture to hope that P |

* Whitney, J. D., ‘‘ Climatic Changes,” p. 321.
+ Howorth, H. 22 ‘Ice or Water,” Vol. IL., p. 492.
t Chamberlin, T, C,, and R, D. Salisbury, “ Geology,” IIL., p. 332.

FORAMINIFERA IN THE DRIFT AT

my criticisms will be readily accepted, yet they may possibly
help in clearing up some points which hitherto could not be
satisfactorily elucidated by other methods. The vast drift
deposits which shroud the country like a great mantle of clay,
sand and stones, frequently contain the remains of the ‘ex-
_ clusively marine group of foraminifera. Mr. Joseph Wright,
a well-known European authority, has shown that the species
of foraminifera have a very wide distribution in European
boulder-clays. And it appears, on the authority of Sir Henry
Howorth,* that Mr. Wright has likewise identified foramini-
fera from American glacial clays. Samples were submitted
to him by the late Dr. G. Dawson from Saskatchewan
River, 1,850 feet above sea-level, from Selkirk in Manitoba,
and from Ottawa. The sample from Saskatchewan contained
specimens of foraminifera referable to recent species, one
of which (Nonionina depressula) is also common in Kuropean
boulder-clays.

It is quite possible that foraminifera may be found in many
other localities in the same clays ; indeed, Sir Henry Howorth

: - mentions that Sir William Dawson had found them generally

diffused in the Pleistocene clays of Canada. This fact, there-
fore, tends to support Colonel Feilden’s + contention that all
the glacial deposits which he had examined in Arctic and Polar
lands, with the exception of terminal moraines now forming
above sea-level, are glacio-marine beds.

Supposing the waters of the Arctic Ocean had risen, per-
haps in consequence of the closing of the Atlantic Ocean,
and had poured into Hudson Bay, overflowing its banks,
and had then crossed the low-lying watershed separating
this northern region from the depressions of the Great Lakes,
the latter would soon have been filled with brackish water,
killing or driving away many of those forms of life that were

4 unable to adapt themselves to this change of conditions. I
ie presume, of course, that troughs, not necessarily like the

lakes now existing, already occupied the same region in pre-
| Glacial times. Such an hypothesis of this area having been
_ invaded by the sea in Pleistocene times is supported by some

* Howorth, H. H., ‘Ice or Water,” Vol. II., p. 216.
t Feilden, H. W., “ Glacial Geology of Arctic Europe,’’ p. 57,

48 ORIGIN OF LIFE IN AMERICA

biological evidence, though it is usually argued that the ocean
crept inland through the St. Lawrence or Hudson River
Valley.

Fifty years have elapsed since Professor Lovén * first drew
attention to the presence of several crustaceans, allied to
marine forms, in Swedish lakes, and endeavoured to prove that
the latter must have been covered by the sea in recent geo-
logical times. One of these crustaceans is the fresh-water
shrimp Mysis relicta, closely related to the common Arctic
marine form Mysis oculata. Since the latter does not occur in
the Baltic, the theory that Mysis relicta is a recent immigrant
from that sea is untenable. It seems much more probable
that it gradually developed from its marine relative Mysis
oculata, when the Arctic Ocean covered the lowlands of
northern Russia, Sweden and northern Germany. This view
is confirmed by the fact that Mysis relicta has now been dis-
covered, along with other marine organisms, in several lakes,
all of which are situated within the area covered by the north
European drift. I have also alluded to its occurrence in
Lough Neagh in Ireland.}

Now it is of great interest that this small fresh-water
shrimp Mysis relicta, which is so closely related to a marine
species, should also occur abundantly in Lakes Superior and
Michigan. First discovered in the stomach of a Coregonus
taken in Lake Michigan by Dr. Hoy, it was subsequently met
with by Dr. Stimpson,f{ living in about fifty fathoms of water
in the same lake. It has since been noticed in Lake Superior
by Messrs. Smith and Verrill, but in no other of the Canadian
lakes. This is in so far significant, as neither of these two
lakes are supposed to have been invaded by the sea in Glacial
and post-Glacial times. All that geologists acknowledge is
that the sea crept up the Hudson River and the St. Lawrence,
as far as the western end of Lake Ontario. The latter and
Lake Champlain had then a marine fauna, and it is there
that we should expect Mysis relicta to occur.

But besides this fresh-water shrimp,. another small

* Lovén, 8., “ Uber einige Crustaceen.”
+ Scharff, R. F., ‘‘ European Animals,” p. 155.
{ Stimpson, A., ‘‘ Fauna of Lake Michigan,” p. 403.

Sheol Radome cee

‘ cpauiaaheblahndaneel teed

ai ——-) —- —_
3 . . 7 .
Se ole aot ge --

RELICT FAUNA OF GREAT LAKES 49

crustacean, called Pontoporeia hoyi, allied to a marine form,
inhabits the Lakes Michigan and Superior, while in the
former still another marine form (Pontoporeia filicornis) and a
remarkable fish called Triglopsis thompsoni have been met with.

Professor Peschel first applied the term “ relict lakes ”’ *
to lakes like those referred to, because they contain the
relicts of a former sea, and the word has since been largely
adopted in the sense in which it was first proposed. Never-
theless, some authorities, notably Professor Credner,+ who
treated the subject most exhaustively, maintain that these
so-called relict animals have either immigrated to the fresh-
water lakes directly from the sea, or have been transported
from their marine habitat by accidental means. He notes
with surprise the absence from all the so-called relict lakes
of marine mollusks or species allied to such, contending that
some of them ought to be found in these lakes, if the latten
had ever been covered by the sea. Professor Credner’s argu-
ments against the relict nature of such lakes as Superior and
Michigan, seem at first sight very convincing. But zoo-
logists are now well acquainted with the fact that all marine
mollusks have free-swimming larvae. ‘These being altogether
a prey to currents would infallibly be swept into the sea if
placed into running fresh water. Thus the parent marine
mollusks would ‘be unable to propagate their kind in fresh

_ water even if they could adapt themselves to it. This circum-

stance seems to account in a satisfactory manner for the
absence of marine mollusks from relict lakes. Quite apart
from this objection to the relict theory, Professor Credner’s
contention of an active migration of marine organisms to
fresh water is particularly inapplicable in the case we have
been considering, because none of the “relict species ”
alluded to occur in the lower lake of Ontario, which, moreover,

' is separated from the upper lakes by the impansable Niagara
_ waterfall. It is of interest also to note that the only other

_ locality in which the fish Triglopsis thompsoni has been
taken, besides that of the Great Lakes, is in tidal pools on the
west coast of Hudson Bay.

* Peschel, O., ‘‘ Vergleichende Erdkunde,”’ p. 167.
+ Credner, R., ‘‘ Reliktenseen,” I., p. 105.

50 ORIGIN OF LIFE IN AMERICA

Other species of fishes related to marine forms live in the
Great Lakes. But we need not suppose that typical fresh-
water fishes are absent. The family of Cyprinids, those
essentially fresh-water fishes to which the carp belongs, is
well represented there. Hence if we suppose that they were
destroyed during the invasion of that region by the sea, the
lakes must, at a subsequent period, have been freely connected
with rivers which were stocked with fresh-water fish. And
it appears that this actually has been the case.

Whether the St. Lawrence was choked by obstructing ice
masses, or whether it was filled with detrital matter carried
down from the neighbouring eastern heights, does not affect
our present inguiries. It seems that after the ice, or, if we
prefer it, after the retreating sea, had left the district, there
were only three lakes instead of the five as at present. These
three lakes, which have been called ‘ Duluth,” “ Chicago ”’
and ‘‘Maumee,’’ were independent of one another. Lake
Duluth emptied its waters into the Mississippi, Lake Chicago
excavated an outlet which has since become the Chicago
drainage canal, while Lake Maumee communicated with the
Wabash River. All, of course, eventually helped to swell the
waters of the Mississippi. Lake Maumee gradually, developed
into the huge Lake Warren. Later on the other lakes joined,
and poured their waters into Ontario, which then communi-
cated with the Hudson by means of the Mohawk River. It
was only then that the sea finally broke down the barrier
which had prevented an overflow into the St. Lawrence, and
advanced as far as the western end of Lake Ontario, one
marine channel communicating with the Atlantic by way
of the Hudson Valley.

We can easily imagine how the fresh-water fishes of the
north, which were either killed or driven south, such as the

redfin (Notropis cornutus) and Notropis atherinoides (it does —

not seem to possess a common name) managed to return to

their northern stations after the Glacial Epoch. Yet I feel .

sure that a survival even of some fresh-water fishes took place
within the drift area in some of the eastern mountain ranges.

Near Freeport in Maine, quite an isolated colony of the ©
beautiful red-bellied dace (Chrosomus erythrogaster) occurs. —
This is probably a pre-Glacial relict. Nor is it likely that —

FISHES OF GREAT LAKES 51

the silver chub (Semotilus corporalis), which only frequents
clear streams, could have spread in post-Glacial times from
the south-eastern counties to the St. Lawrence basin. ‘Two
more examples might be mentioned that are practically,
confined to the drift area and they are among the most
interesting geographical puzzles of North America.

The first of these is the mud minnow (Umbra limi), a
small minnow-like fish frequenting muddy and reedy ponds
near the Great Lakes as far east as Quebec. A closely allied
species lives in streams and ponds in the eastern States from
Connecticut to South Carolina. The only other relative of
these two little fish, in fact the only other member of the
family of mud-minnows (Umbridae), is Umbra krameri found
in Hungary. Dr. Gill* gives a most interesting account
of their habits.

Blanding’s pond tortoise (Emys blandingi) is the second
example I have in my mind. It is a small species, the black
carapace or shell being dotted all over with numerous yellow
spots. It is entirely confined to the drift region from
Wisconsin in the west to New Hampshire in the east. It
agrees with Umbra in so far as its only relation inhabits
Europe. ‘The European species (Emys orbicularis) is
common in central and southern Europe. A map of its range
is given in my work on the Huropean animals.t

A more striking instance of a case of survival within the
glaciated, or drift area, is afforded by the fresh-water pearl-
mussel (Margaritana margaritifera). Being an immensely
ancient species which no doubt originated in North America,
it has taken advantage of old land connections to invade
Kurope and eastern Asia. In North America it occurs within
the ancient eastern land-mass in several localities, notably
in Labrador, on Newfoundland and Anticosti Islands, in
the Quebec province and in New England.{ From its western
station in the lower Saskatchewan it is separated by a
tract of over one thousand two hundred miles in which
it is unknown. ‘This discontinuous distribution implies

* Gill, Theodore, “ The Umbras.”’
+ Scharff, R. F., ‘‘ European Animals,”’ p. 179.
t Walker, Bryant, “ Distribution of Margaritana margaritifera,” p. 127.

E 2

52 ORIGIN OF LIFE IN AMERICA

the destruction of the species in the drainage area of the
Upper St. Lawrence. What other cause but the Glacial
Epoch can be assigned for this partial destruction? And
in explanation of this and other similar cases it seems
reasonable to conclude that certain areas within the drift
region were entirely free from the devastating agency, be it
land-ice or the sea, which destroyed so much of the pre-
existing fauna and flora. We might argue, of course, that the
pearl-mussel had advanced northward in two independent
streams in post-Glacial times, one along the Mississippi valley
and the other along the Atlantic coast, and that they had thus
reached the northern habitats alluded to. But quite apart
from the difficulties connected with pushing its way along
the coast from river to river, there seem to me to be no
grounds for such a supposition. The fact that Margaritana
margaritifera is the only fresh-water mussel (Naiad) belong-
ing to the Atlantic river system which is now found living
within the Mississippi drainage area, shows how inconceiv-
ably slowly these mollusks spread. The fresh-water mussel
fauna, so characteristic of the Mississippi drainage area, is
believed to have descended in a scarcely broken line from that
of the Cretaceous Period, and many recent forms are only
distinguishable with difficulty from those that lived in those
remote times.

However, the question of survival or non-survival in the
drift area is not confined to the instance alluded to. Lampsilis
(Unio) borealis, Lampsilis superiorensis, Anodonta mar-
ginata,. Anodonta kennicotti, and Anodonta pepiniana are all
restricted in their range to the drift area, and are not known
to have ever lived outside it.*

There is no doubt ample zoological evidence for the assump-
tion that many species of vertebrates and invertebrates
survived the Glacial Epoch within the area commonly sup-
posed to have been covered by vast ice-masses. But there
is another important point which the geographical distribu-
tion of the fresh-water pearly mussels may elucidate. Several
times I have referred to the theory that in pre-Glacial times
the land between northern Labrador and eastern Massa-

* Simpson, C. T., ‘‘ Synopsis of pearly freshwater mussels,”

|

FRESH-WATER PEARL MUSSELS 58

_chusetts was raised to a much higher level than it is now,
and that it has gradually sunk to its present position. If this
had been the case, the rivers on the western side of this
highland would have drained westward and would have
formed part of the Mississippi drainage, while the eastern
streams would have emptied their waters straight into the
Atlantic. The latter ought therefore to show distinct signs
in the composition of their fauna of having been isolated
from the Mississippi drainage system. Dr. Simpson de-
scribes the fresh-water pearl-mussels of the Mississippi
drainage system as large, ponderous and ornamented with
beautiful and odd patterns of colour and sculpture. The
waters that drain into the Atlantic on the other hand are
inhabited by a totally different set of mussels. They are
' moderate in size, frail and not remarkble for either colour
_ or sculpture. Only very few of the eastern species extend

(q westward to the head waters of the St. Lawrence.*

| In the interesting report on the Pleistocene fauna and flora
_ already cited, there is a list of twelve species of fresh-water

- mussels that have been observed in the Don valley deposits.

_ None of them belong to extinct species, though it is a signifi-
cant fact that nearly one half of them no longer inhabit the
_ St. Lawrence drainage, being now confined to the Mississippi
and its tributaries.
_. This certainly implies that the Mississippi was more inti-
' mately connected with the upper St. Lawrence system in
_ early Glacial and probably in pre-Glacial times than. it is now,
_ for it is not unjustifiable to assume that these southern forms
_ found their way northward before the commencement of the
Glacial Epoch. It is possible that those southern species,
_ found in the Don deposits, which still have a wide range in
tg Canada, may have survived the Glacial Epoch in that country.
| Dr. Simpson { pointed out that almost all the Mississippi
_ valley species of mussels now living in St. Lawrence drain-
“age area have become more stunted and more simple in
_ outline, while their characteristic sculpture and colours are
* Simpson, ©. T., ‘‘On some Fossil Unios.” pp. 591—592.
- fT Dawson, J. W., D. P. Penhallow, &c., ‘‘ Canadian Pleistocene Flora
ES and Fauna,’’ p. 331.
|} Simpson, C. T., ‘On Mississippi Valley Unionidae,”’ p. 384.

54 ORIGIN OF LIFE IN AMERICA

nearly obliterated. This change in form is so striking,
says Dr. Simpson, that many of these northern races of
Mississippi mussels have been described as distinct species.
Dr. Simpson is of opinion that this remarkable change in
form among the Mississippi species inhabiting the St. Law-
rence drainage system has been produced since the Ice Age
began to draw to a close, because, he argues, it is almost
certain that all fluviatile and lacustrine life under the ice
sheet was destroyed.

The prevalent geological opinions as to the nature of the
Ice Age thus dominate all biological thought in reference to
problems of distribution. If we emancipate ourselves from
these pre-conceived notions in our speculations on the origin
of the existing fresh-water mussel fauna, we must arrive at
different conclusions.

Two almost diametrically opposed theories have been pro-
pounded to explain the origin of the geographical features
of the river system of north-eastern North America in pre-
Glacial times. According to Professor Grabau,* Mr. Warren
Upham and Professor I. C. Russell are of opinion that the
greater part of the Laurentian basin formerly discharged its
waters southward to the Mississippi. With this view Professor
Grabau agrees. Much of the Archaean region in north-eastern
North America must have stood greatly higher than at present,
the slope of the land being toward the south-west. Two great
rivers then existed, according to Professor Grabau, in place
of the present Great Lakes, the Saginaw and the Dundas
Rivers, both of them draining into the ancient Mississippi.
Dr. Spencer is in agreement with Dr. Grabau in so far as he
contends that the land stood at least two thousand feet higher
than at present. He differs from the other writers in his
belief that the lake region and the more north-easterly high-
lands were equally affected by the uplift, so that the rivers
which replaced the lakes in pre-Glacial times drained into
the St. Lawrence just as the waters from the lakes do now.+

The first of these two theories seems to me to explain the
origin of the eastern fauna in a satisfactory manner. The

* Grabau, A. W., ‘“‘ Geology of Niagara Falls,” pp. 42-—é4.
+ Spencer, J. W., ‘Falls of Niagara,” pp. 400-—405,

\

HISTORY OF THE GREAT LAKES 55

other does not. We may suppose that the species inhabit-
ing the Mississippi during the period preceding the Ice Age
were not precluded from advancing up stream towards the
highlands of Labrador. But only the hardiest forms, those
that could adapt themselves to waters probably brackish and
laden with mud, might have succeeded in surviving, though
not without becoming stunted in form and undergoing
various other changes. Such forms as the pearl-mussel
(Margaritana margaritifera), accustomed to pure mountain
streams, only survived in isolated localities in the eastern and
western parts of its range, becoming extinct in the central
parts, where the conditions must have been less favourable for
its survival. | |

Let us now examine the land fauna of another part of
this north-eastern Archaean land surface which is supposed
by Professors Upham and Grabau to have stood at a rela-
tively much higher level to the lake region than it does at
present. Labrador has been amply dealt with, but New-
foundland, which must have been completely isolated from
the mainland for some time past, being a large island situated
at the mouth of the mighty St. Lawrence River, ought
to contain some interesting pre-Glacial relicts. We have no
reason to assume that Newfoundland has been connected
with the mainland since the passing away of the Ice Age,
nor is there any evidence to show that mammals or other
terrestrial vertebrates have reached the island by swimming
across the Strait of Belleisle or down the St. Lawrence.
Geologists tell us that Newfoundland was not overridden
by the huge Labradorean glacier, but that it had a system
of local glaciers quite independent of those of the mainland.
Even if all the higher parts of the island had been buried
in snow and ice, tracts of land near the coast must have
remained free from ice, as in Greenland, and so have given
shelter to the survivors from pre-Glacial times. This view
is certainly strengthened by the fact that all the mammals
hitherto observed on the island belong to well-marked varieties
or species peculiar to it. The Newfoundland caribou, the
only deer inhabiting the island, has antlers differing con-
spicuously from those of other races of reindeer, and many
authorities now recognise it as a distinct species under the

56 ORIGIN OF LIFE IN AMERICA

name of Rangifer terraenovae. All reindeer are expert
swimmers, yet the Newfoundland reindeer or caribou has
never been known to cross over to the mainland. _ The follow-
ing other species of mammals are all peculiar to Newfound-
land. The Newfoundland musk rat (Fiber obscurus), the
Newfoundland vole (Microtus terraenovae), the Newfound-
land arctic hare (Lepus bangsi), the Newfoundland lynx
(Lynx subsolanus), the Newfoundland fox (Vulpes deletrix),
the Newfoundland otter (Lutra degener), the Newfoundland
marten (Mustela atrata). A bear and a wolf are also said to
occur.

The fauna of Newfoundland, moreover, is characterised by
the remarkable absence of all such mammals which we might
reasonably expect to have come from Asia in comparatively
recent geological times, such as the moose, wapiti deer, brown
bear and many smaller species. The island does not seem
to have been affected by the great stream of new-comers which
poured into the country and reached other parts of eastern
America, such as Nova Scotia.

In speaking of the present land bird fauna of Nova Scotia,
Dr. Trotter argues that it was derived from two faunal
stocks, a more primitive boreal one which occupied the region
from remote times, and a later transition fauna which in-
vaded the peninsula. since the re-elevation of the previously
sunken isthmus. He speaks of this as a “‘ venturesome state-
ment,” yet he suggests that many boreal types belonging
to the genera Pinicola, Carpodacus, Loxia, Spinus, Sitta,
Regulus, Certhia and Parus may have occupied Nova Scotia
even during the Glacial Epoch, since glaciers do not preclude
forest growth, while food must have been abundant during
the short breeding season.*

It has been my intention in this chapter to briefly direct
attention to the extreme north-east as one of the salient’
bio-geographical features of the American continent. More
than fifty years ago Professor L. Agassiz spoke of “the
zoological island of New England,” which he described as
‘encircled by a uniform combination of fresh-water animals,

* Trotter, Spencer, ‘‘ Land Bird Fauna of North-Eastern America,”’
p. 226.

Pe eee ee eee oS a H “—w

ANIMALS OF NEWFOUNDLAND 57

_ being itself isolated in character and approaching more to
_ that of the Old World.* He was then unaware that this z0o-
- logical island, which his keen insight and judgment had
- recognised, extended really far to the north of New England,
_ that it formed part, in fact, of the north-western prolongation
_ of the European continent in late Pliocene times, preserving
until the present day many characters in common with the

Old World.

* Agassiz, L., ‘‘ Fishes of the Tennessee,” pp. 363—364.

CHAPTER III
THE CANADIAN NORTH WEST

Leavine Newfoundland, the St. Lawrence and the region
of the Great Lakes on our north-westward travels, we now
enter the drainage area of the mighty Mackenzie River which
conducts its muddy waters to the Arctic Ocean. We
know from Mr. A. H. Harrison’s* recent exploit that it
is possible to journey down the one thousand eight hun-
dred miles from the Athabaska landing and reach the Arctic
Ocean entirely by boat. But we obtain a better idea of the
fauna and flora of this vast Athabaska-Mackenzie region by
crossing the country on foot, or by a perusal of the excellent
report lately published by the biological survey of the United
States Department of Agriculture. The task of furnishing
this report was entrusted to Mr. Edward A. Preble,} a natura-
list who already had the advantage of accomplishing the diffi-
cult survey of the Hudson Bay region, and who had shown
himself possessed of the necessary qualifications for such an
undertaking. :

The Mackenzie basin comprises a vast region of nearly
700,000 square miles, or about six times the size of the
British Islands. As is usually the case in regions covered
by glacial drift, the country is studded with innumerable
fresh-water lakes extending in a more or less connected system
from Lake Superior to the Arctic Ocean. With the exception
of a large area in the north, which is mainly outside the actual
drainage basin of the Mackenzie, much of this region is
entirely covered with forests. The principal trees are white
and black spruce, the canoe birch, tamarack, aspen and balsam

* Harrison, A. H., “ In Search of a Polar Continent.”
+ Preble, E. A., ‘‘ Athabaska-Mackenzie Region.” Compare also
Macfarlane, R., ‘‘ Mammals of North-West Territory.”

THE MACKENZIE BASIN 59

poplars, Banksian pine and balsam fir. ‘With these are asso-
ciated, generally in the form of undergrowth, a variety of
shrubs, some of which have a continuous distribution through
the forest zone, whereas others are more or less restricted
in range. But the whole region between Hudson Bay and
the mouth of the Mackenzie River is by no means all forested.
North of a line drawn from the mouth of the Churchill River
to the mouth of the Mackenzie, the country belongs to what
are known as the “ barren-grounds,” which have already been
alluded to in previous chapters. ‘They are largely covered
with short grass, moss and small flowering plants interspersed
with patches of sedgy or peaty soil on which grow Labrador
tea, crowberries, dwarf birches, and willows. Both flora
and fauna, in fact, remind us vividly of certain parts of Green-
land and Labrador.

The only large mammals, as in Greenland, are the barren-
ground caribou and the musk ox. The former is simply
spoken of as the ‘“‘ deer” by the northern hunters. Zoologi-
cally it belongs to the barren-ground form (Rangifer arcticus)
which, as I remarked, seems to be closely allied to the Green-
land reindeer. It is not so with the musk ox, as Dr. Kowarzik
has recently shown. After a very careful and extended ex-
amination of a number of skins and skulls of musk oxen
from this region, he was able to show that they differed from
those living elsewhere by the possession of a deep lachrymal
pit and two mammary glands. The Greenland musk ox, which
belongs to the eastern group, has no lachrymal pit and four
mammary glands. There are other minor differences clearly
proving that Dr. Kowarzik’s * Ovibos moschatus macken-
zianus is much more than a mere race. It is, in fact, a species
perfectly distinct from the one inhabiting Greenland. In
spite of these differences, the casual observer is easily misled
by the apparent external resemblances among all the musk
oxen.

The general similarity in the fauna of the Mackenzie
region and that of Greenland is by no means super-
ficial, and holds good to some extent even among the smaller
kinds of beasts. The arctic hare seems much like the Green-

* Kowarzik, R., ‘‘ Der Moschusochs und seine Rassen,”’ p. 120.

60 ORIGIN OF LIFE IN AMERICA

land hare, and the lemmings resemble the creatures we have
already met in the same country. Yet there are two perfectly
distinct kinds of lemming in these barren-grounds. In winter
they are easily discriminated since one of them does not
change its rusty brown fur, while the other (Dicrostonyx
hudsonius) becomes white all over. The former we have not
met with before. It neither occurs in Greenland nor in
Labrador, and appears to be a more recent immigrant
to North America. This supposition is strengthened by
the fact of the occurrence of this lemming (Lemmus
trimucronatus) from Alaska as far east as Melville Penin-
sula. In Alaska even another species of the same genus
(Lemmus minusculus) occurs, and on the Pribilof Islands
still another, the black-footed lemming (Lemmus nigripes)
Beyond Bering Strait in eastern Asia other kinds make their
appearance, whilst in Europe the common lemming (Lemmus
lemmus) was well known long before the days of Linnaeus.
Its remains having been discovered in many Huropean caves
along with those of other arctic animals, it is not unreason-
able to assume that the genus Lemmus is of Old World origin
and one of the many Asiatic immigrants that have invaded the
North American continent in the past, though only a few of
the latter have chosén the inhospitable barren grounds for
their home.

Another new form which we have not met with before
is the ground squirrel known as the Hudson Bay spermophila
(Citellus parryi). It is abundant all over the barren-ground
region alluded to, the earth being occasionally riddled with
their burrows. These “‘ spermophiles ” or “ gophers ” as they
are sometimes called, occupy a somewhat intermediate posi.
tion between squirrels and marmots. Numerous species are
known from North America, altogether about forty. In Asia
and HKurope there are fewer kinds of spermophiles, yet they
do occur, and this circumstance, while tending to prove once
more that Bering Strait was dry land, renders the search
for the original home of the genus more difficult. The fact
that in Europe Citellus(Spermophilus) only inhabits the east,
having invaded the continent in Pleistocene times, and then
retreated again towards the country whence it came, points
to Asia as the home of the spermophiles. On the other hand,

LEMMINGS AND GOPHERS 61

the remains of Citellus douglasi have been recorded from
Potter Creek cave in California, and those of Citellus tride-
cemlineatus from the Conard fissure in Arkansas. Both of
these deposits are regarded as Pleistocene in age.* If these
caves were in Hurope they certainly would be held to be pre-
Glacial, for about fifty per cent. of the species contained in
them are extinct, while Mastodon, Megalonyx and other
ancient forms accompany the spermophiles-in the Cali-
fornian cave. The two spermophiles alluded to are still
living in North America and have a wide range. If the genus
had invaded Alaska from Asia in Pleistocene times, it is
scarcely credible that there would have been time for the
development of the two species and their enclosure in these
distant caves within the Pleistocene Period, especially when
we consider that the whole of Canada is believed to have been
buried under a thick mantle of ice. It is possible, of course,
that there were two distinct invasions into North America of
the genus Citellus, one having entered from the west, as I
shall explain later.on, in Miocene times, the later one from
the north-west towards the end of the Pliocene Period.

Among the carnivores of the barren grounds, the barren-
ground bear (Ursus richardsoni), the wolverine (Gulo luscus),
and the barren-ground wolf (Canis occidentalis albus) are .
the most noticeable.

I have scarcely as yet attempted to bring the study of
the geographical distribution of birds within the scheme of
this present work, partly because our knowledge of their past
history is so defective in comparison with that of many other
groups, and partly because mountain ranges or narrow
channels of the sea do not as a rule afford effective barriers
to their dispersal. Occasionally, however, birds are extremely
circumscribed in their range, and there can be no doubt that a
study of their geographical distribution is well worthy of care-
ful attention. If I had not a superabundance of better material
for my purpose, I should gladly dwell a little longer on the
problems suggested by their range. Many of them, however,
are quite useless for our purpose, loons and auks, for instance,
two groups of arctic birds attached to the sea coast. Many

* Brown, Barnum, ‘Conard Fissure,” pp. 166—167.

62 ORIGIN OF LIFE IN AMERICA

others are circumpolar but too migratory. Only the genus
Lagopus is of special interest, because it occurs in all the
regions and countries so far discussed. It includes the
American and Old World ptarmigans and the Huropean
grouse, all of which are more or less permanently resident in
the countries they inhabit.

The willow ptarmigan iGagbnus albus) breeds in the
barren-grounds and further south. It has a very wide range,
inhabiting northern Asia, northern Russia, and northern
and central Seandinavia. It is not found in Greenland or
Newfoundland, being replaced there by the rock ptarmigan
(Lagopus rupestris). The latter also lives in Iceland,
western Asia, arctic America and Japan. The third American
species is the white-tailed ptarmigan (Lagopus leucurus)
which frequents the Rocky Mountain summits from Alaska
to New Mexico. It is sometimes called the “ white or snow-
quail.” Besides the willow ptarmigan, we have in Europe the
common ptarmigan(Lagopus mutus), the red grouse(Lagopus
scoticus), peculiar to the British Islands, and Lagopus hyper-
boreus of Spitsbergen and Franz Josef Land. Long ago I
ventured to express the opinion that the genus Lagopus was
of North American origin having thence spread to Europe
and Asia.*

Dr. Stejnegerf has since pointed out that, by an unfortunate
oversight, I had included Greenland in the range of the willow
ptarmigan instead of the rock ptarmigan. He also argued
that the willow ptarmigan of Scandinavia is more likely to
have originated from the British red grouse than, as I thought,
vice versa. Though I still believe that the genus had a
North American ancestry, I quite concur with Dr. Stejneger
in the view that the points he raised cannot be reconciled
with the conclusions I formerly arrived at. The subject is
certainly worthy of further careful study. At any rate, this
instance shows clearly the much greater difficulties we have
to contend with in tracing the geological history of birds
than that of mammals.

As we proceed southward from the barren-grounds we first

* Scharff, R. F., ‘“‘ History of European Fauna,”’ p. 336.
Tt Stejneger, L., ‘‘Scharff’s European Fauna,” p. 105.

AMERICAN PTARMIGANS 63

enter a belt of more or less stunted timber before reaching the
real forest. Yet even here quite a number of new forms of
animal life are met with that are quite absent in the more
northerly districts. They are mostly species occurring also
in the forest zone of western Labrador. In referring to them
in the last chapter, I alluded more fully to the geological
history of the moose(pp. 32—83), but I dwelt also on the fact
that the flying squirrel, musk rat, chipmunk, woodchuck and
others made their appearance as soon as we entered the
forest from the east. And it is precisely these forms of animal
life that make such a change in the appearance of the fauna
as we leave the Mackenzie region barren-grounds on our
way to the great Canadian forest region.

The flying squirrel (Sciuropterus sabrinus) of northern
Canada and arctic America is also found further south. Other
species of the same genus inhabit the United States. The
skin at the sides of its body extends between the limbs in
such a manner as to act like a kind of parachute, but nothing
in the nature of actual flight takes place. The flying
squirrel is rarely seen, being an entirely nocturnal crea-
ture. The distribution of these flying squirrels is decidedly
interesting. They are found from Florida to Alaska, and
are only known as fossils from the Potter Creek Cave in
California. They have almost certainly been in the country
since Pliocene times. Hence Sciuropterus yukonensis, which
is peculiar to Alaska, has, in all probability, survived the
Glacial Epoch in that country. On the western side of Bering
Strait, in Kamchatka, another species is found whose range
extends westward as far as Scandinavia. Southward, as
we cross China into Burma and India, we still encounter
species of flying squirrels, and even on the islands of
Java, Sumatra and Borneo. And all these belong to the same
genus Sciuropterus. Such an extensive distribution implies
that the genus must be an ancient one, and, indeed, we ara
acquainted with several species of Seiuropterus from the
Miocene and Pliocene deposits of France. This in itself is
no proof that the flying squirrels originated in Europe. They
may have spread there from Asia in later Tertiary times and
have subsequently died out in Europe, only to be re-estab-
lished more recently from a later Asiatic invasion. In any

>.

64 ORIGIN OF LIFE IN AMERICA

case, the presence of flying squirrels in America seems to be
due to a migration from Asia, and that this took place at a
time when a land bridge existed between the two continents
is evident. |

The musk rat (Fiber zibethicus) * derives its popular fame
chiefly from the fact that thousands of its skins are annually.
exported from North America by the fur traders. Having
adopted the more attractive name of “‘musquash”’ for these
skins, the dealers have no difficulty in disposing of them. Like
beavers, these creatures inhabit subterranean burrows on the
banks of lakes and streams, and are expert swimmers, yet they.
are really more allied to the voles. Varieties of the common
musk rat are met with from the Mackenzie River to Labrador
and southward as far as New Mexico. In the Yukon district
and westward Fiber spathulatus replaces the common musk
rat; and far to the east in Newfoundland the district dusky
musk rat (Fiber obscurus) occurs. Only two other living
kinds of musk rat are known to science. One of them

‘inhabits the State of Oregon, the other the dismal swamp |

in Virginia. This genus, therefore, is one of the most
typically North American we have noticed so far, and no
doubt it has originated in North America. This view is
entirely confirmed by fossil evidence, for no musk rat
remains are known outside North America. The common
musk rat has been observed in the Pleistocene deposits
of South Carolina, New Jersey, and Pennsylvania, while
the jaw of an extinct species (Fiber annectens) has been
found by Mr. Barnum Browny in the Conard fissure of
Arkansas. The remarkable circumstance about this jaw is
that the teeth it contains strongly resemble those of Neofiber,
a sub-genus of Microtus. Hence this cave species forms a
connecting link between the genera Fiber and Microtus, and
this fact supports the opinion I ventured to put forward
(p. 29) as to the American origin of the latter.

Before describing some’ of the other small beasts, I must
refer now to an animal which is not only the largest living
terrestrial American mammal, but likewise one that we, from

* Hollister, N., ‘Synopsis of Muskrats.”’
+ Brown, Barnum, ‘Conard Fissure,” p. 197.

Thee eet aly ;
i Sse

_
A

Fia@. 5.—Map of North America, showing the original distribution of the Bison (lightly
shaded), the range of the same animal after the completion of the Union Pacific
Railroad (darkly shaded), and the present range in Yellowstone Park (black).
(Reproduced with Dr. Hornaday’s permission.)

[ To face p. 65.

HISTORY OF THE BISON 65

a European point of view, are accustomed to associate above

all with North America, namely, the bison, or so-called buffalo.

The bison (Bison bison) is now almost extinct in its wild
state, yet here in the Mackenzie region, a little to the south of
the Great Slave Lake, are still found some wild herds of this
magnificent creature, the last remnants of the millions that
once roamed over the continent.

Dr. Howard* contributed many years ago an interesting
article to “‘ Science” on the manner in which insects and
other creatures are disseminated over the States through the
agency of man. An equally instructive paper might be written
on the manner in which man has been the means of destroy-
ing a portion of our fauna. For no one can doubt that human
agency alone is responsible for the rapid destruction of the
bison and other animals.

When the Spaniards landed in America in the year 1521,
the bison was still plentiful in Northern Mexico. In the com-
mencement of the following century the English found it in
abundance in the neighbourhood of the present site of the city
of Washington. No doubt the range of this huge ungulate
extended over about one-third of the entire continent of North
America. The extreme south-eastern limit was on the coast of
Georgia. The western boundary was in New Mexico. From
these two southern localities to the shores of the Great Slave
Lake in Canada, vast herds of bison were known to exist even
in the early parts of the last century. According to Dr.
Hornaday’s + graphic description, they lived and moved, as no
other quadrupeds ever had, in great multitudes, like grand
armies in review, covering scores of square miles at once.
They were so numerous that boats were sometimes stopped
by them in the rivers, and they threatened to overwhelm
travellers on the plains. In later years they occasionally
derailed locomotives and cars. One herd, seen by Colonel
Dodge in 1871, only forty years ago, and described by him,
extended for a distance of twenty-five miles and must have
included a million individuals. The Indians believed that
these buffaloes issued from the earth continuously, the

* Howard, L. O., ‘‘ The Spread of Species by the Agency of Man.”
+ Hornaday, W. T., ‘‘ Extermination of American Bison.”

L.A- F

66 ORIGIN OF LIFE IN AMERICA

supply being consequently inexhaustible. As long as these
wild tribes only possessed the bow and arrow, bisons were
comparatively safe from their depredations, in spite of the
great drives that they were accustomed to organise. On the
introduction of firearms, the Indians assisted civilised man
to the best of their ability in his utterly wanton destruction
of these helpless creatures. The building of railroads across
the continent naturally hastened the process of extermination,
the completion of the Union Pacific line dividing for ever
the bisons of the United States into two great herds. These
subsequently became known as the northern and southern
herds. The great slaughter of the bison really only began

in 1871. Four years later the southern herd had ceased to ©

exist. The year 1881 witnessed a similar destruction of the
northern herd, and at present this most picturesque and im-
pressive member of the American fauna is practically extinct
in its wild state, but for the small herds alluded to in northern
Canada (see Fig. 5). There are other small herds preserved
in the Yellowstone Park and in some reservations in western
Canada. In them the bison can no longer be said to live
altogether in the wild state.

I mentioned that the bison was looked upon as one of the
most typically American species. Nevertheless, we have in
eastern Hurope a bison which is closely allied to the American
species, and from the circumstance that it formerly roamed
over a large part of that continent, it might be argued that its
cousin from the New World is but a new-comer and in no way
typical of America. A certain amount of support for that
argument might be derived from the well-known fact of a
Pliocene bison (Bison sivalensis) being known from India
and Java and another from China. But in America there are
likewise bison remains (Bison alleni) which were considered
by Professor Marsh to belong to the Pliocene series, while
Professor Cope described one even from Nicaragua and
Southern Mexico (Bison scaphoceras). More recently, how-
ever, Dr. Lucas* has clearly demonstrated that Cope’s bison
is a sheep, and that Marsh’s specimens are probably referable
to the lower Pleistocene, so that it does seem likely after

* Lucas, F. A., ‘‘ Fossil Bisons of North America,” pp. 756—766.

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WAPITI DEER 67

all that the ancestors of the American bison came originally
from Asia. The exact geological period of this supposed
Asiatic invasion will be discussed in the next chapter, when we
come to deal with Alaska. Some other extinct bisons are
known from America besides those alluded to. Bison crassi-
cornis, according to Dr. Lucas, is confined to Alaska. Mr.
Lydekker,* on the other hand, considers it identical with
Bison priscus, an extinct bison which ranged throughout
arctic Siberia and a large part of Hurope.

South of the belt of stunted timber lie the vast forests
of the Athabaska and Peace River valleys, and a great zone
of warmer country abounding in animal life, as we proceed
in the same direction. A noble representative of the deer
tribe which we meet here reminds us of the Huropean red
deer. In the States it is commonly known as the elk (Cervus
canadensis), though it has no connection with the moose,
which in Europe is known by that name. In Canada it is
more generally called “ wapiti deer.” While the range of
the moose seems to be on the increase in the Mackenzie
Region, it is curious that the wapiti has become almost extinct
in the northern parts of its former geographical range, and
now only occurs there in small numbers.

Mr. Thompson Seton f tells us that originally, that is to
say about the beginning of the sixteenth century, the wapiti
was found from the Mackenzie Region as far east as Boston,
and as far south as Arizona and Alabama (see Fig. 6). Its
destruction proceeded unchecked until the year 1895, when a
change in public opinion took place. Henceforth the wapiti
was protected; and it is now actually on the increase in
Manitoba and along the Rocky Mountains from Alberta to
the borders of New Mexico and also along the Pacific States.

The wapiti has only been observed in a fossil state in
Pleistocene deposits. We know from these records that its
range extended in Pleistocene times southward as far as
Florida and from North Carolina to New Jersey and Kentucky.

The resemblance between the American wapiti and, at any

* Lydekker, R., ‘‘ Catalogue of Fossil Mammalia,” IT., p. 24.
+ Seton, Ernest Thompson, “ Life Histories of Northern Animals,” I,
p. 43.
F 2

eS ORIGIN OF LIFE IN AMERICA

rate, the eastern European races of the red deer is so close
that Dr. Caton * was sometimes at a loss to discriminate
between them. The late Professor Nehring} also drew atten-
tion to the resemblance of certain fossil deer antlers from
central and eastern Europe to those of Cervus canadensis.
As we proceed westward in Kurope the distinctive cha-
racters of the red deer become more prominent, and less so
as we travel towards America through Asia. Dr. Tcherski,t
I think, was the first to direct attention to the fact that the
wapiti was a variety of the Siberian maral. And a similar
opinion has more recently been expressed by Mr. Lydekker. §

It is many years since I argued that the Klaphus group of
the genus Cervus, to which the Canadian wapiti and thle
European red deer belong, originated in Central. Asia, and
I have not had any cause to modify my views in this respect.||

Cervus canadensis differs from all other American deer and
agrees with the great majority of the Old World forms in so
far as the proximal portions of the lateral metacarpal bones
persist. This is, as Sir Victor Brooke first pointed out, an
important structural character. In the possession of these
small leg-bones the Canadian wapiti stands entirely apart
from its more distant relations of the American Continent,
while clearly betraying its close relationship to the Siberian
maral and the Old World deer generally. Its presence in
America, therefore, forms one of the most powerful argu-
ments in favour of the view that North America and Asia
have been united by land within fairly recent geological
times. We shall meet with so many similar examples during
the course of this work, that one might almost be inclined to
say that the matter requires no further proof, that it is an
established fact. Notwithstanding, one of the most distin-
guished authorities in America is not disposed to accept the
view that there was such a recent land connection. Nor is
it expedient for us to adopt the attitude of the modern
glacialist who, in referring to the theory of the presence of

* Caton, J. D., ‘Antelope and Deer of America,”’ p. 214.

+ Nehring, A., ‘‘Tundren und Steppen,” p. 203.

t Tcherski, J. D., ‘‘ Das Janaland, &c.,” p. 496.

§ Lydekker, R., ‘‘ Geographical History of Mammals,” p. 315.

' Scharff, R. F., ‘‘ Mammiféres de la région holarctique,” p. 448.

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ORIGIN OF WAPITI DEER 69

gigantic glaciers during the Ice Age, exclaims “this is no
vain hypothesis or speculation founded on uncertain data,
no mere conjecture which the light of future discoveries may
explode. The evidence is so clear and so overwhelmingly
convincing that we cannot resist the inevitable conclusion.’’*

The Canadian wapiti deer is a typical example of a recent
Asiatic immigrant. In some previous cases it was doubtful
whether the species referred to was of truly American or
Asiatic origin. ~Again in others we were able to trace a
distinctly American ancestry, but not beyond the more recent
deposits.

I want now to mention an interesting creature whose
lineage we can follow through several geological ages, and
whose most remote ancestors had, as we might say, not
a drop of foreign blood in their veins. The species I allude
to is the Canadian tree porcupine (Erethizon dorsatus). It
is in many respects a most striking and remarkable animal.

In Europe, in fact everywhere in the Old World, porcu-
pines are ground animals, and they usually dig their
burrows in the earth. The American porcupines differ from
them in many important anatomical characters. They, more- —
over, all live on trees, and generally have prehensile tails.
We have here two entirely distinct groups, as among the deer,
though externally all porcupines have a strong family like-
ness. As far as trees grow right up to the barren-grounds the
Canadian porcupine was once abundant, but yielding whole-
some food and being easily killed it has been exterminated in
many districts. Whenever it is undisturbed itis plentiful, feed-
ing on leaves and bark, and it seems entirely unaffected by
climatic extremes. ‘The Canadian tree porcupine lives in
Canada from the Rocky Mountains in the west to southern
Labrador in the east, and enters the United States in Maine
and New Hampshire. formerly it occurred all along the
Alleghenies, through Pennsylvania into Virginia and Ken-
tucky to Arkansas. In these southern parts of its range it
no doubt fell an easy prey to the Indian hunters who were
always fond of its flesh. The destruction of forests on the
arrival of the white man hastened its northward’ retreat.

* Geikie, James, ‘‘ The Great Ice Age,” pp. 67—68.

70 ORIGIN OF LIFE IN AMERICA

There is no sign here of a post-Glacial centre of dispersal
south of the drift area. The centre of dispersal, on the con-
trary, lies in Canada and it is from there that it has spread
southward. Yet the species had already come into existence
when the sabre-tooth tiger and peculiar kinds of peccaries
haunted the forests of Arkansas, for its remains have been
found together with these extinct creatures in the Conard
fissure.* It likewise lived in Pennsylvania at a time when
the great Mylodon, Megalonyx and Mastodon still flourished
there. |

Beyond the Mackenzie Region, in the far distant Alaska,
there lives another porcupine very closely related to the
Canadian species. This yellow-haired porcupine (Hrethizon
epixanthum), as it is called, ranges from Alaska through
the Rocky Mountains and westward to the Pacific as far south
as northern Mexico, thus exhibiting the same indifference
to climatic conditions as its near relative. Both of these
North American porcupines have short tails. In Mexico,
Central and South America we meet with numerous species,
all allied to Erethizon, but with prehensile tails, which
considerably assist them in climbing trees.

Now if the genus to which these tree porcupines belong had
originated in Alaska or Canada, we should certainly expect
it to have traversed Bering Strait into Asia while the wapiti
deer and many other Old World forms poured into America.
That it has not done so does not tend to disprove the assump-
tion of the former existence of a Bering Strait land bridge.
It only implies that the genus Erethizon is of southern
origin, and has merely spread northward within recent geo-
logical times. The south-western region, that vast country
of mountains and plains which contains the most important
centre of dispersal in North America, has no doubt given
rise to the genus Erethizon. Of its past history we know
nothing as far as North America is concerned. South’ of
Mexico, as already stated, all tree porcupines possess pre-
hensile tails, and are distinguished by other minor differ-
ences from Erethizon. For these reasons they have been
placed into the distinct genus Coendu. These southern forms

* Brown, Barnum, ‘‘ Conard Fissure,”’ p. 166,

q
f
‘

CANADIAN TREE PORCUPINE 71

of tree porcupines have apparently advanced northward along
the isthmus of Central America and have reached Mexico
within quite recent times. There are no grounds, however,
for the supposition that Erethizon is a modified Coendu.
When North and South America became joined by the exist-
ing isthmus of Central America in Pliocene times, Erethizon
no doubt was already an inhabitant of the northern continent.
Since the two genera belong to the same family Coendidae,
which differs fundamentally from the Old World family
Hystricidae, we must assume that long anterior to the Plio-
cene Period North and South America, or such portions of
those continents which then existed, had already been united
and then become disconnected again. These theories are
not founded on zoogeographical data alone. Professor
Osborn * urges on palaeontological grounds that North and
South America were joined in Cretaceous and perhaps in
early Tertiary times, and then separated again until the
Pliocene.

All this ‘will be discussed in detail when we come to deal
with Central America. I only mention the matter now
because in the Santa Cruz beds of Patagonia the skeleton of
a peculiar tree porcupine has been discovered and placed
by Dr. Ameghino into the new genus “ Steiromys.’” More
recently, Professor W. B. Scott} re-examined these Steiromys
remains, and noted the remarkable fact that they are more
like the recent Erethizon of North America than any of the
modern South American tree porcupines. He even argues
that Steiromys is the direct ancestor of Erethizon.

As this implies a former land connection between Pata-
gonia and North America, independently of the remainder
of South America, it largely aided me in the theoretical
construction of an ancient land bridge between south-western.
North America and Chile.t It is on this land bridge, I think,
_ that the ancestor of the North American Erethizon wandered

northward from Patagonia in early Tertiary times. All this
will be more fully explained later on.

* Osborn, H. F., “ Progress in Mammalian Palaeontology,”’ p. 99.
tT Scott, W. B., ‘‘ Report of Princeton Expedition,” V., pp. 413—417,
{ Scharff, R. F., ‘‘ Harly:Tertiary Land-Connection,” p. 521,

.

72 ORIGIN OF LIFE IN AMERICA

It may be of interest now to inquire as to how far a group
of less mobile creatures than the mammals, the snails, for
instance, can be classified into species whose ancestors were
Asiatic, and such as were originally native to the soil. Of
course we need only consider snails resident in the Atha-
baska—Mackenzie Region. A direct European influence
among the fresh-water molluscan fauna is apparent, since
certain species such as Limnaea stagnalis, L. truncatula, L.
palustris, and Aplexa hypnorum inhabit the Mackenzie
Region as well as Hurope. How they have spread to America
is not readily ascertainable. The points of resemblance
between the two regions are clearly of long standing, but none
of these species need necessarily have come from Europe
direct, as they all inhabit Siberia as well as Canada.

Among the land snails we also meet with forms familiar
to the European conchologist, such as Pupa muscorum,
Cochlicopa lubrica, Hyalinia radiatula, H. nitidula, Euconu-
lus fulvus, Zonitoides nitidus, and others. All these are no
doubt very ancient species, too ancient in fact to help us
materially in our present inquiries. It is possible, moreover,
that they have special facilities for accidental dispersal, that
is to say for dispersal other than the ordinary mode of pro-
gression on land, although my studies have not led me ‘to
believe in the efficacy of such a mode of conveyance in
permanently stocking a country. ?

The strictly American Pupa armifera and P. holzingeri,
Vertigo ventricosa, V. ovata, Vitrina limpida, Patula solitaria,
and P. striatella are all easily transported by flooded streams,
and thus scattered far and wide. In spite of the fact that the
land and fresh-water mollusks of the Mackenzie Region
indicate that a distinct Old World influence is recognisable,
nothing points definitely to a recent land connection with
either Europe on Asia. They do not confirm the view that any
survival of the molluscan fauna through the Glacial Epoch
has taken place in that region. On the contrary, the absence
of species peculiar to the region implies, as among the
mammals, that that part of America has only recently been
stocked with animals from another portion of the continent.
Whether we assume that gigantic glaciers covered the coun-
try, or whether we argue that the ocean invaded it, the

s

SNAILS OF THE NORTH WEST 78

ultimate effect would be somewhat similar. In reality it
would not be quite the same, because in the latter case it is
conceivable that the whole Rocky Mountain chain, which lay
to the west of the flooded territory, could have supported a
fairly rich fauna and flora. Ifa huge glacier really existed
- in the Keewatin district, it is imconceivable to suppose that
any but the most scanty fauna and flora could have found a
stray asylum on the few isolated ‘“ Nunatakkr” projecting
beyond the Rocky Mountain ice-fields.

The mollusks do not favour either theory. The mammals,
on the other hand, show clearly a geologically recent invasion

_ of Old World-forms from the west, which is more compatible

with what I may call the marine theory.

Mr. Walker * contends that the Glacial Epoch was a great
factor influencing the distribution of the North American
molluscan fauna. I can only perceive signs of local destruc-
tion. The distribution of the land and fresh-water mollusks

i. in North America took place evidently long before this Glacial
‘ Epoch, and was not seriously influenced by the latter.

Both theories will be more fully dealt with in the next
chapters in which the animals, principally of Alaska, will be
described. These animals afford us more material for our
_ inquiries, being of great importance to the just appreciation
and understanding of the varied origin and development of
the American fauna.

* Walker, Bryant, ‘‘ Origin and Distribution of Mollusca,” p. 53.

CHAPTER IV

THE FAUNA OF ALASKA

Sincr Alaska came into the possession of the United States
its progress has been a rapid one. The sudden development
of the resources of this vast country attracted public atten-
tion and led to urgent demands for further exploration of its
natural wealth. This work has been actively prosecuted
within the last few years, so that we now possess some know-
ledge of the geography, geology and mineral resources of the
country. Situated in the north-westerly extremity of North
America, its area equals in size about one fifth of the United
States (see Fig. 1). It is nearly three times as large as the
German Empire.

A broad mountain belt spreads along the Pacific coast of

Alaska, its western prolongation being still recognisable in the —

chain of the Aleutian Islands. The north-eastern extension of
the Rocky Mountains curves rapidly westward on reaching the
Arctic Ocean and there forms a range almost parallel with the
north coast of Alaska. Between these two mountain systems
lies partly a plateau and partly a great plain drained by the
Yukon River, the latter sending its waters into the Bering
Sea. About one quarter of Alaska lies within the Arctic
Circle. Hence, from the standpoint of geographic position,
it must be regarded as an Arctic province. The southern
sea-board, on the other hand, which is exposed to the warm
winds and waters of the Pacific Ocean, gives a comparatively
mild climate to the entire southern portion of the territory.

Thus Dr. Brooks * draws attention to the fact, which few of

us probably realize, that the range of climate in Alaska is
greater than that between Maine and Florida.

The capital of the country, Sitka, has a slightly lower mean

* Brooks, A. H., ‘‘ Geography and Geology of Alaska,” p, 11.

> ail *
a ee

GLACIERS AND VOLCANOES 75

temperature than Scotland, but it has a much greater rain-
fall. This enormous precipitation on the Pacific coast has
a striking effect on the vegetation. The whole of south-eastern
Alaska is densely timbered with forests of spruce and hem-
lock, also red and yellow cedar and other trees, their luxurious
growth contrasting strongly with the open forests of the
interior and the more northern treeless barren-grounds. Yet
the lowlands of the interior are usually well wooded with
spruce, cottonwood, birch, willow and alder. At a height of
from about 2,000 to 3,000 feet above sea-level, forest growth
ceases altogether. Here the climate becomes continental in
character, with great extremes of heat and cold. In the
northern parts of the country the surface everywhere is
covered with dense growth of moss and grass, with an
abundance of wild flowers, whereas the ground beneath is
perpetually frozen.

Alaska possesses many other features of unrivalled interest.
The magnificent peaks clustering about Mount Fairweather
as a centre, and containing Mount St. Elias, Mount Logan
and Mount McKinley, the latter with a height of 20,400
feet being the loftiest mountain in North America, have
excited the just admiration of those who have been fortunate
enough to visit this region. Splendid glaciers here and there
descend from the great mountain valleys down to sea-level,
while further west we notice in Mount Wrangell a fine example
of an active volcano. The vast glaciers have given rise to
the popular idea that Alaska is a country of unlimited snow
and ice. Asa matter of fact they are almost entirely confined
to the Pacific mountain system.

Near the sea border the climate is, as I mentioned, much
milder than in the interior of the country, yet an abundant
precipitation from the warm moisture-laden winds here pro-
duces the extensive snow-fields from ,which the glaciers are
fed. On the land side of the Pacific Mountain range glaciers
are very poorly developed. Further inland they are entirely
absent.

Since a vast area of land in Alaska remains snonwaned by
ice, in spite of a low mean temperature, we must recognise the
dustice of Professor Whitney’s assertion, that a still greater
increase of cold would not cover those regions with ice, nor

76° ORIGIN OF LIFE IN AMERICA

bring about the conditions of a Glacial Epoch. On the con-
trary, it is evident that the opposite result would take place.
The conditions of a Glacial Epoch, says Professor Whitney,
are not to be sought for in a general diminution of tem-
perature. “ Itis true,” he argues, “ that the regions in which
the glaciers take their rise cannot be so warm that precipita -
tion takes the form of rain; but the required low temperature
must be confined to a limited area, and be brought about by
local causes, and not be something in which all the other
portions of the earth are sharers. There must be copious
precipitation, which, although locally in the form of snow,
can in reality only be the result of a high mean temperature
in other regions. In short, warmth, as a phenomenon of
general occurrence, is more indispensably necessary than cold,
because the latter may always be produced, where locally
wanted, by increase of elevation or by the shifting of the
ocean currents.’’*

We now know that the glaciation of Alaska during the
Ice Age must be regarded as an extension of the present
system of glaciers. They were no doubt considerably larger,
while glaciers also existed in the Endicott range in north-
western Alaska. Nevertheless, no signs of former glaciation
have as yet been discovered in the interior of the country.
The latter is now generally believed to have been entirely
unglaciated. If we adopted Professor Whitney’s views, and
endeavoured to picture to ourselves the conditions of Alaska in
the Glacial Epoch, we must imagine the Pacific to have been
warmer than it is now and the climate of Alaska much milder
and more humid. A more luxuriant flora would, under such
circumstances, have been able to flourish in-the interior of the
country, and consequently a richer and more varied fauna.

And how much is this conception of the Glacial Epoch at
variance with the theories generally propounded! I may be
excused, for example, for again citing Professors Chamberlin
and Salisbury’s + words, that one of the most marvellous
features of the ice-dispersion during the Glacial Epoch was

* Whitney, J. D., ‘‘ Climatic Changes,” p. 388.
+ Chamberlin, T. ©., and R. D. Salisbury, ‘‘ Geology,” Vol. III.
pp. 332—333,

ee ee = ee eee Oe a ee

ALASKA DURING ICE AGE ae’ |

the pushing out of the Keewatin ice-sheet from a low flat
centre, without even a suggestion of a mountainous nucleus,
to one thousand miles westward, while the Rocky Mountain
glaciers were thrust eastward, but little beyond the foot-
hills.

The ice from this great centre of dispersion is supposed
to have reached the mouth of the Mackenzie River close to
the borders of Alaska. Nevertheless, the same authors ac-
knowledge that the plains of Alaska were apparently free from
glaciation, even during the time when, two thousand miles
further south, the waters of the Ohio and the Missouri were
actually believed to have been turned from their courses by the
encroaching ice-sheets. How can we reconcile the co-existence
of these two extraordinary and altogether anomalous climatic
conditions in adjoining parts of the same continent ? Surely
there must be some mistake. At present there is far less pre-
cipitation of moisture in the Keewatin region of Canada than
in any of the western mountain ranges. The existing con-
ditions of land and water must consequently have been entirely
altered during the Glacial Epoch. Indeed, even our concep-
tions of the nature of climates would have to undergo some
change ‘before we can realize how this stupendous ice-sheet
in the Keewatin region came to be built up, while Alaska was
only able to form a few local glaciers. In a previous chapter
(p. 46) I ventured to make some critical remarks on the
supposed gigantic ice-sheets of the Glacial Epoch, and I hope
to show now that the biological evidences are altogether op-
posed to the views that the Ice Age was an epoch of excep-
tional cold. My criticisms on the current beliefs in the land-
ice theory are by no means new. We need only peruse the
fascinating volumes entitled “Ice or Water ” published by

_ Sir Henry Howorth, in which the claims of water as a power-

ful agent in the formation of so-called glacial deposits are
ably discussed. My object, however, in writing this work was
not to investigate the origin of the Ice Age. This short
digression into the domain of glacial geology merely serves
to acquaint the general reader with some of the special
difficulties we have to contend with in explaining certain
phenomena connected with the Alaskan fauna.

Since the beginning of the last century it was known that

78 ORIGIN [OF LIFE IN AMERICA

fossil ivory might be gathered on the shores of Alaska.
Several Russian authorities reported on its occurrence. there,
animadverting to the fact that the remains of elephants had
also been discovered on some of the Pribilof Islands. Within
recent years several expeditions have been sent to Alaska
from the United States with a view to discovering more about
these and other remains of extinct animals. The first of these
was dispatched by the Smithsonian Institution of Washington
in 1904. Mr. Maddren, who had already visited the country.
several times and had travelled extensively in the interior,
was charged with the expedition; and he issued an interesting
report on his return.

He contends that the lowest beds in Alaska in which
mammoth remains occur are the “ lacustrine silts,” which
form an extensively developed feature in the country.
Scattered through these Pleistocene deposits we find remains
of skeletons, isolated cheek-teeth, tusks and bones, the animals
to which they belonged having probably died near the shores
of the lakes in the bottom of which they became embedded.
These fluvial and lacustrine beds of Alaska, with their occa-
sional gravels, rest unconformably on the eroded surfaces
of the older formations. At the time the silts and clays were
forming Alaska was for the most part, according to Mr.
Maddren,* a low-lying country, characterised by enlarged
rivers with slow drainage, and many lakes.

The general conclusions arrived at by Mr. Maddren are,
“that while remnants of the large Pleistocene mammal herds
may have survived down to the recent period, and in some
cases their direct descendants, such as the musk ox, have
done so, most of them became extinct in Alaska with the close
of the Pleistocene. The most rational way of explaining this
extinction of animal life, says Mr. Maddren, is by a gradual
alteration of the climate from more temperate conditions, per-
mitting of a forest vegetation much further north than now,
to the more severe climate of to-day. Recent changes, while
checking the vegetation and thus reducing the food supply,
have acted injuriously on animal life, only leaving those
forms that were capable of adapting themselves to the new

* Maddren, A. G., ‘‘Smithsonian Exploration in Alaska,’ pp. 25-—28.

eee ore _— .
IA. _ e Sie ae a . ee 7 Ps *
a ee ee ee ee oe ae ee

EXTINCT MAMMALS OF ALASKA 79

conditions. Mr. Maddren urges that there are no facts to sup-
port the contention that the climates of the Arctic and
sub-Arctic regions ever had been colder than they are at
present. He thinks that there are no phenomena presented
by the past history of these regions that require a more
severe climate than that now existing to account for them.
There are no ice deposits in Alaska, he says, except those of
large glaciers, that may be considered of Pleistocene age.
There are no ice-beds, he continues, interstratified with the
Pleistocene deposits of Alaska. Finally he argues that the
various forms of land ice, together with the deposits of peat,

now existing.throughout the Arctic and sub-Arctic regions
_ of Alaska, belong to the Recent Period, and that these deposits
_ may be most conveniently and logically classified by their
_ position with reference to the Pleistocene and Recent forma-
) tions, and that the ice deposits cannot be differentiated satis-
factorily into deposits of snow or water origin by their

St physical structure and character alone.*

_ A second Smithsonian expedition to Alaska was dispatched
a few years later under Mr. Gilmore. He noticed that the

|. scattered remains of Pleistocene animals occurred throughout

| : the unglaciated region of Alaska and the adjacent Canadian
| territory in three distinct deposits, viz., in what is locally

known as “ black muck,” which is accumulated in the valleys

| of the smaller streams, then in the silt and clays already.
| referred to, and finally in the more recent fluvial and alluvial
| beds. The best-preserved remains were obtained in the muck
| deposits, and in these occurred certainly several examples of
| primary entombment. A magnificent skull with tusks of the
| mammoth was discovered in the muck forty-two feet below

the surface, near Dawson, in the Yukon territory in north-
western Canada. Mr. Gilmore} is convinced that the
determinable species of mammals found are sufficient to

| show at once that they represent, a typical Pleistocene

fauna, some of them, such as the moose, caribou, musk ox,

sheep, bear, and beaver, having persisted down to the present

day.

* Maddren, A. G., “Smithsonian Exploration in Alaska,” pp. 65—66.
+ Gilmore, C. W., ‘‘Smithsonian Exploration in Alaska,” pp. 26—88.

80 ORIGIN OF LIFE IN AMERICA

The complete list of mammals is as follows :—

Mammoth (Elephas~ primi- Extinct musk ox (Symbos-

genius). tyrelli).
Mastodon (Mastodon ameri- Bison (Bison crassicornis),
canus). », (Bison occidentalis).
Horse (Equus sp.). », (Bison alleni).
Moose (Alces sp.). Sheep (Ovis sp.).
Reindeer (Rangifer sp.). Bear (Ursus sp.).
Musk ox (Ovibos sp.). Beaver (Castor sp.).

The results of these two expeditions excited so much interest
in the United States that another was sent out to Alaska by
the American Museum of Natural History under Mr.
Quackenbush.* He was fortunate enough in discovering part
of a mammoth skeleton which still retained the flesh, skin
and hair similar to those found in northern Siberia. This
discovery is of particular interest, as it elucidates an extremely
important feature connected with the preservation of the soft
parts of mammoths in Siberia. It has been stated that the
preservation of the bodies of mammoths is due to their being
embedded in underground ice. Mr. Gilmore informs us that
fossils in Alaska have never been found in pure ice masses.
On the contrary, he makes it quite clear that the flesh, skin
and hair of the mammoth were preserved to the present time
because they had been pressed down into the soft mud by the
weight of the rest of the body. All that remained exposed
of the body rotted away. The author agrees with the previous
writers in considering the mammoth and the mammalian re-
mains as Pleistocene. He argues that the climate of this
period must have been somewhat milder than that of the
present time, because large trees had been met with associated
with these mammalian remains in regions which are now tree-
less. He also adds Bodétherium bombifrons, the wapiti deer
and the wolf to the Pleistocene species already known from
the Yukon territory of Canada.

From these three most valuable reports we can gather cer- .

tain remarkable facts which are apparently antagonistic to

* Quackenbush, L. S., ‘Alaskan Mammoth Expeditions,” pp. 125—

127.

FORMER CLIMATE OF ALASKA 81

the theory of the existence of enormous ice-sheets in dis-
tricts adjoining Alaska during Pleistocene times. All the
writers agree that the numerous mammals whose remains were

_ discovered in Alaska lived there in the Ice Age during climatic

conditions which were vastly more favourable than those now
prevailing. Evidences of a milder climate are furnished by
the abundance of mammoth remains in Alaska. Horses, rein-
deer and herds of bisons likewise roamed all over the country.
Hence rich meadows and forests must have been plentiful
to support them all with food. Nothing whatsoever has been
brought to light which would sustain the theory expressed
by some writers that this fauna inhabited Alaska during a
mild post-Glacial or inter-Glacial stage. No trace of the exist-
ence in Alaska of a cold period preceding the supposed inter-
Glacial or post-Glacial stage has been found. We must con-
clude, therefore, that Alaska and the neighbouring countries
during the whole of the Pleistocene Period hadi a temperate
climate.

These heterodox views on the climate during the so-
called Ice Age are not new. They were enunciated by
Sir Henry Howorth and supported by able arguments
more than twenty years ago. Very little was then known
of Alaska, but the remains of innumerable large mammals
had been unearthed in northern Siberia and even on the New
Siberian Islands situated in the Arctic Ocean. These dis-
} closures naturally caused a good deal of speculation. They
| led to the conclusion that the cold of the Ice Age or Glacial

a Epoch was succeeded by a warm or temperate climate during

which these animals were tempted to wander into the Arctic
Regions. After carefully examining the problem, however,
Sir Henry Howorth * expressed the conviction that this mild
or temperate epoch did not follow the Ice Age, but pre-
_ vailed during the whole of it. The creatures alluded to must,
therefore, have lived in those northern regions during the

| Pleistocene Period, which was temperate in character. Since
| the close of that period Siberia has gradually become more

and more inhospitable.
A few years later the extremely valuable scientific results of

* Howorth, H. H., ‘‘ Mammoth and the Flood,” p. 265.
L.A. G

82 ORIGIN OF LIFE IN AMERICA

Dr. Tcherski’s * expedition to the New Siberian Islands were
published by the Academy of Sciences in St. Petersburg; and
it is of interest to note that he arrived at conclusions similar
to those of Sir Henry Howorth. He contended that the causes
which produced glaciation in Europe acted in quite a different
manner on the conditions of life in northern Siberia, where
the climate remained as a direct continuation of that pre-
vailing in Tertiary times, so that this country had a higher
temperature during the Pleistocene Period than obtains at
present.

He looks upon Siberia as a country in which the processes
of general refrigeration of the northern hemisphere and the
deterioration of the conditions of existence for plant and
animal life during the post-Tertiary Period took a regular
and steady course.

Baron von Toll concurs with Tcherski and other writers in
their opinion that the large mammals whose carcases and
skeletons are now unearthed in the extreme north of Siberia
really lived there, but he urges that they did not arrive there
until after the Glacial Epoch. Underground ice, as in some
parts of Alaska, is extensively met with in northern Siberia
and in the New Siberian Islands. Its occurrence, according
to Baron von Toll, is due partly to a recent origin in crevices
and lateral infiltration, partly to a former glaciation of Siberia,
the ice having been preserved as “ relict ice ” from the Glacial
Epoch. Being a follower of those who connect that period
with a universal lowering of temperature, his contention is
that northern Siberia enjoyed a milder climate in post-Glacial
times, and that the mammoth, horse, rhinoceros and other
mammals were thereby induced to visit the shores of the Arctic
Ocean and the New Siberian Islands, which, according to

Baron von Toll,+ were then connected with Siberia and arctic
America.

The mammoth and many other animals, as I have indi- | q

cated, invaded America from Asia. Consequently, if we can
determine whether a land connection existed between the
two continents, how long it lasted, and what species made use
of it in their travels, some valuable data may be obtained as a

* Tcherski, J. D., ‘‘Das Janaland,’’ p. 469.
+ Toll, Eduard von, ‘ Die fossilen Hislager,” pp. 80—85.

ASIATIC INVADERS IN AMERICA 83

basis for discussion of some of the problems referred to.
Other attractive inquiries, such as the influence of the Glacial ©
Epoch on animal migrations, might be elucidated. With the
climatic problem alone are connected so many important geo-
logical speculations that the subject is well worthy of a most
careful scrutiny.

At a meeting of the Biological Society of Washington about
ten years ago the theme chosen for discussion was the sup-
posed former land bridge between Asia and North America.
Dr. F. A. Lucas spoke in favour of a geologically recent brief
land connection, and supported his theory by the geographical
distribution of the wild sheep and the brown bears of North
America, both of which have their near relations in Asia.
He also pointed to the remains of mammoth and bison in
Alaska as evidence of the same view. An older land connec-
tion, he thought, was indicated by the occurrence of a fossil
Nemorrhaedus in Colorado and of Elephas columbi. Dr.
Theodore Gill concurred with the last speaker, and suggested
that the presence in America of such species of fishes as the
pike and Scaphirhynchus tended in favour of the older land
connection. Mr. F. V. Coville dwelt upon the importance of
plants in sustaining the view of a transient and geologically
recent land bridge. Additional testimony in favour of an
old land connection of long duration was brought forward by
Dr. Stejneger. He particularly emphasised the occurrence
in Asia and America of the alligator and the salamander
Cryptobranchus. Dr. W. H. Dall alone dissented from the
opinions expressed, urging that such mammals as_ the
mammoth might have crossed over Bering Strait by an ice-
bridge which he thought might have joined North America
and Asia during the Glacial Epoch.*

Dr. Dall + gave no reasons for his aversion to the belief
in a geologically recent land connection between North
America and Asia; although, in acknowledging that north-
eastern Asia and Alaska have certain species of land and
fresh-water mollusks in common, he recognised the intimate
relationship existing between the two areas.

* Lucas, F. A., Th. Gill, and others, ‘‘ Former Land Connections.”

+ Dall, W. H., ‘‘ Mollusk Fauna of Alaska and Eastern Siberia,”
pp. 365—366.

a 2

84 ORIGIN OF LIFE IN AMERICA

The problem at issue is obviously not to be solved by the
application of purely geological reasoning. Dr. Brooks, in
his splendid contribution to the geology of Alaska, carefully
avoids any discussion of a former land connection with Asia.
In his brief statement that a land bridge between Asia and
North America could only have been utilised for Glacial or
post-Glacial migrations of Asiatic types, Professor Suess *
does not make us acquainted with the reasons for his supposi-
tion that the land connection did not also exist in Pliocene
times. He alludes to the striking circumstance that the
hypothetical land bridge was used apparently by Asiatic types
only, and leaves us wondering why American types should
not have taken a similar advantage of pouring into Asia.
That, however, is part of the problem which we must reserve
for a later stage of the discussion.

Dr. Matthew + does not share Professor Suess’ opinion,
for he indicates a wide land connection, and Professor Osborn
follows him in that respect, between North America ‘and
north-eastern Asia in the Bering Sea region in Oligocene,
Miocene, Pliocene and Pleistocene times.

As a rule the opinions of geologists on this problem are
based on biological evidence alone. It is the latter, there-
fore, that we have to rely upon. Curiously enough, Mr.
Knopf { maintains that all the stratigraphical testimony from
which conclusions of some positiveness can be drawn, record
only epochs of more widely-spread submergence and in-
creased separation of the continents, although he recognises
the strength of the palaeontological demands in favour of
more or less continuous inter-continental communications.
I shall endeavour, now, to critically examine the problem
from that point of view. I have already had several oppor-
tunities of expressing my own views on this subject (pp. 32
and 68), and these are entirely in favour of a geologically
recent Bering Strait land bridge (see Fig. 7). - But we require
to know more than this. We want evidence which will lead to
the determination of the geological age of the bridge and the

approximate date of its beginning and end.
* Suess, R., “ Antlitz der Erde,”’ Vol. TII., p. 764.

+ Matthew, W. D., ‘‘ Hypothetical Outlines of Continents.”
} Knopf, A., ‘‘ Probable Tertiary Land Connection,” p. 419,

De F
[USER Bites Ro bc

a. ee Se ee

a

ae Eos OT Re on ee

ee eo

ASIATIC AFFINITIES OF ALASKA 85

Dr. Allen* considers the inter-relationship of the boreal
mammals inhabiting North America and northern Asia so
intimate that it could only have been brought about by the
existence of a geologically recent land bridge connecting the
two areas. He thinks that most of the more northern forms
of mammal life on the two continents are probably the slightly
modified descendants of types which formerly had a con-
tinuous circumarctic distribution, and which have become
slowly differentiated, mainly, no doubt, since the disruption
of the former land connection at Bering Strait.

Every naturalist who casually surveys the boreal fauna
of North America and northern Asia must be struck by the
apparently large predominance of Asiatic invaders in North
America, such as the moose, bison, wapiti deer, American
wild sheep, glutton, brown bears, the now extinct mammoth
and many others, over the American element in Asia. In
fact, we scarcely recognise any signs of an exodus having
taken place in the opposite direction. ‘Typically American
mammals, such as the common American musk-rat, the por-
cupine, the black bear, and others, for example, have repre-
sentatives in Alaska, nevertheless they are quite unknown
on the western shores of the Bering Sea. At the same time
Dr. Allen draws our attention to the occurrence along the
Siberian and Kamchatkan coasts of certain mammalian types
that are of distinctly American origin. ‘These are a species
of weasel (Putorius pygmaeus) closely related to the arctic
American weasel (Putorius rixosus), and only remotely akin
to any Kurasiatic species; a spermophile (Citellus buxtoni),
closely allied to the boreal American Citellus paryi; the Kam-
chatkan bighorn (Ovis nivicola), which is more nearly related
to American forms of sheep than to Asiatic ones, and several
others.

Whether the presence of these closely connected forms on
both sides of Bering Strait proves the case of an American
invasion of Asia appears to me still somewhat doubtful,
especially as the sheep (Ovis) is, as far as we know, of Old
World origin. A sheep is known from the Pliocene Forest
Bed of England, while it only appeared in America in

* Allen, J. A., ‘‘ Mammals from North-Eastern Siberia,” p. 183.

86 ORIGIN OF LIFE IN AMERICA

Pleistocene times. Moreover, the Kamchatkan sheep (Ovis
mivicola) is generally looked upon as a very near relation
to another Siberian wild sheep also inhabiting part of Kam-
chatka, and which has been found fossil by Tcherski in the
New Siberian Islands, viz., Ovis borealis. To judge by the
recent as well as by the fossil sheep in America, the genus
Ovis, to which all sheep belong, must, I think, have pene-
trated to North America, together with the mammoth and
other mammals, in comparatively recent geological times.
I shall return to the distribution of the American sheep
later on.

I should have thought the genus to which the musk ox
(Ovibos) belongs was a better example of an American
intruder into Asia. Although no longer inhabiting the Old
World, its incursions into Asia and Hurope must have taken
place about the same time as the mammoth’s advent in
America. A still more striking instance of an American in-
vader into Asia is the camel, although Professor Osborn’s *
statement, ‘‘ in the Pleistocene the camels wandered into Asia
from America, while the bears passed them en route to
America,” can scarcely be considered as strictly correct,
since two kinds of camels are known from the Pliocene
Siwalik deposits of India. The brilliant researches of
American palaeontologists have long ago acquainted us with
the fact thatthe camel family (Camelidae) inhabited America
since the dawn of the Tertiary Hra, while the Indian occur-
rences alluded to are the earliest indications of camels having
reached the Old World. It is in Pliocene times, therefore,
or earlier even, that a land connection between America and
Asia must have existed, for no one would venture to propound
the theory that camels could have crossed from one continent
to another on an ice bridge.

Sir Henry Howorthy collected in 1892 some valuable testi-
mony showing that'the mammoth had lived in western Europe
in pre-Glacial times. In the following year Dr. Tcherski t
reminded us that a complete skeleton of the mammoth was

* Osborn, H. F., ‘‘ Faunal Relations of Kurope and America,” p. 58.
+ Howorth, H. H., “The Mammoth and the Drift.”
{ Tcherski, J. D., ‘‘ Das Janaland,”’ p. 474.

MAMMOTHS IN ALASKA 87

discovered in an undoubtedly pre-Glacial deposit at Troizkoje,
near Moscow. ;

In Alaska the mammoth is the only elephant that has been
found fossil. In the United States its remains are associated
with those of two other elephants, viz., Elephas columbi and
Elephas imperator, which, according to Professor Osborn,*
are analogous to the European Elephas antiquus, and EH.
meridionalis. The ranges of these species overlap, yet their
distribution seems to imply that the mammoth was the last-
comer, or that it became modified in structure further south,
giving rise to the two other species of elephants. The de-
posits in. which the mammoth occurs in the United States
are generally looked upon as Pleistocene. But in the Potter
Creek Cave in California it is associated with Mastodon,
Megalonyx and other types belonging to extinct genera.}
This cave contains nearly fifty per cent. of extinct species,
and if situated in Hurope would probably be classed among
Pliocene deposits.

Similar cases illustrating the invasion of Asiatic types by
way of Alaska, and their apparent modification in character
as they travelled southward, occur in almost all groups of
animals. Sometimes, however, we meet with instances that are
very difficult to explain by the assumption of their ancestors
having utilised the land bridge alluded to. The magpie (Pica
rustica), for example, is a handsome and strikingly coloured
bird inhabiting the whole of Europe, North Africa, central
and eastern Asia and western North America. Various races
and varieties are recognisable among the Asiatic magpies,
while the north African form is likewise distinct. Curiously
enough, the American variety resembles the European form
more closely than it does any of the Asiatic ones, and it occurs
from Alaska to Mexico, and eastward as far as the Missouri
River, whereas no magpies at all have been noticed in the
extreme north-east corner of Asia. The distribution is there-
fore somewhat discontinuous, the most easterly district in
Asia where it is known being southern Kamchatka. In the
extreme south-west of its American range in southern

* Osborn, H. F., ‘‘Mammalian Palaeontology,” p. 111.
+ Brown, Barnum, ‘Conard Fissure,” pp. 167—168.

83 ORIGIN OF LIFE IN AMERICA

California quite a peculiar yellow-billed magpie has arisen,
which is sometimes distinguished by the name of Pica nutalli.

It is not at all evident that the ancestors of these American
magpies entered America by way of Alaska, and yet if mag-
pies had originated in America there would probably be many
species there; at any rate, they would inhabit the whole of the
continent, and perhaps central America as well. Being con-
fined to the west, and differing but slightly from Old-World
forms, their origin points to Asia. At the same time the fact
that the American magpie is more like the European form
than the Asiatic one is a feature which cannot be lost sight
of. Dr. Diederich discusses the problem whether the
American magpies arrived in America before or after the
Glacial Epoch. In spite of the fact that magpies in America
are entirely migratory and have lived on the continent suffi-
ciently long to develop the peculiar Californian race just
referred to, Dr. Diederich * inclines to the belief that they
entered the New World in post-Glacial times. Without any
fossil or other evidence to guide us, it is difficult to express
an opinion on this subject. But it seems to me that the
magpie should be placed into one group with a good many,
other forms of animal life which reached North America long
before that event, as I shall more fully describe in one of
the subsequent chapters.

Dr. Gill, as I mentioned above (p. 83), expressed the
opinion that the occurrence of Scaphirhynchus in Asia pointed
in favour of an older land connection between that continent
and North America. ‘The fish known in America as the
shovel-nosed sturgeon (Scaphirhynchus platyrhynchus) is
abundant in the river system of the Mississippi to which it
is confined. It is now known that its nearest relatives are
two species inhabiting central Asia which are no longer classed
with Scaphirhynchus, but are placed into the distinct genus
Kessleria. All these ganoid fishes belong to a very ancient
group, most of which are extinct. The skeleton of the
ganoids is generally cartilaginous, and they retain many
other archaic characters in their anatomical structure.
Another example is the paddle-fish (Polyodon spathula). It

* Diederich, F., ‘‘ Verbreitung der Elstern,” p. 51.

THE FISHES OF ALASKA —_—89

likewise lives in the Mississippi and its tributaries, while its
next of kin, Psephurus gladius, occurs in the Yangtse Kiang
and Hoang Ho rivers in China. These also are ganoid fishes
and, like the true sturgeon and bony pike, are the only few
remaining members of a very ancient and formerly abundant
group of fresh-water fishes. The fact of their survival in
these two continental centres might tempt us to adduce these
instances in support of the theory stated above, that Asia
and North America were recently connected with one another
by land, whereas the migration of these fishes is an old story
dating back to some remote geological period when, their ances-
tors no doubt spread from one continent to the other by means
of a land connection which probably lay further south. Their
geographical distribution has obviously nothing to do with
the subject under discussion, which concerns a geologically
recent event. The cat-fishes-or horned-pouts (Ameiurus)
are possibly of a more recent origin. They swarm in every
quiet stream and pond, especially in the eastern States of
America. A single species (Ameiurus cantonensis) is found
outside the American continent, viz., in China. Finally
I may mention that the “ suckers ’’ (Catostomus), which are
very numerous in the American streams, are confined to
North America, with the exception of one species (Catog-

tomus rostratus), which inhabits eastern Siberia. The last

case certainly indicates a former land connection between

_ North America and Asia, and consequently a dispersal from

the former to the latter, at a geologically recent date. Still
in the present state of our knowledge we are unable to deter-
mine whether the passing across to Asia of these fishes coin.
cided with that of the great mammals whose dispersals I
have endeavoured to elucidate.

It is impossible to discuss the relationship of all the Asiatic
to the Alaskan groups of animals, but no matter what class or .
order we examine with a view to testing this kinship, we
find among almost all of them some indications of it. Dr.
Horvath,* for instance, recently dwelt on the large number of
species of Hemiptera (a group including bugs and allied
insects) common to Hurope and North America. He quoted no

* Horvath, G., ‘ Faunes hémiptérologiques,” p. 7.

>

90 ORIGIN OF LIFE IN AMERICA

less than a hundred and twenty-two species found in temperate
and northern Europe, and also in North America, reasoning
that since the greater number of them also live in northern
Asia they must have spread from one continent to another
across Bering Strait. He does not definitely state that he
considers the Strait to have been a land surface at the time
these species are supposed to have passed across it. Still he
emphasises the intimate relationship of the Alaskan and the
opposite Siberian shore fauna, by citing the names of four
species of Hemiptera which are confined to these two
countries.

A rather striking example clearly illustrating the gradual
advance of a genus across Asia, and its final immigration
into North America, is shown by Parnassius, a genus of
butterflies to which the European “‘ Apollo” belongs. The
Apollo group of butterflies originated, according to Mr.
Austaut, towards the latter part of the Tertiary Hra in Asia,
at the time when some of the great mountain chains of that
continent were being formed. I alluded to the HKuropean
species of Apollo in my work on Huropean Animals, gave a
map of their distribution and enlarged upon their origin. Iam
in full agreement with Mr. Austaut’s views as to the Asiatic
centre of dispersal. The only point in which I differ is with
regard to the period of its origin, which [I believe to have
been considerably earlier than Mr. Austaut* thinks likely.

In Europe we possess only three species of Parnassius,
whereas there are thirty-five in Asia, Turkestan being the
richest country in Apollos. Some species are peculiar to the
Altai Mountains in Siberia, and as we go eastward new forms
replace those with which we had become familiar. In Amur-
land there are others, and yet when we cross Bering Strait to
Alaska we still meet with an Apollo (P. nomion) which also
occurs in the Altai Mountains, while the Californian Apollo
(P. clodius) is very closely related to Parnassius clarius of
these same mountains. The Asiatic character has thus been
retained by two of the American species. ‘Two others, Par-
nassius thor of Alaska and Parnassius sminthus, are quite
distinct from any others, indicating that the passage from

* Austaut, J. L., ‘‘ Les Parnassiens,’’ pp. 62—63.

AMERICAN APOLLOS 91

Asia to America of the genus is not a recent event. It
must have taken place at a time sufficiently remote from
the present to permit the gradual evolution of the two new
species from the ancestral forms. This may possibly have
coincided with the eastward advance of the mammals referred
‘to. A land connection in the neighbourhood of Bering Strait
would certainly have facilitated the dispersal of these butter-
flies and other insects just as much as that of mammals.

In a discussion on the relationship of the Asiatic and North
American forms of another genus of butterfly (Vanessa), Dr.
Standfuss * also supported the theory of the former land con-
nection between Asia and North America in pre-Glacial times.
The Glacial Epoch, he contends, subsequently segregated
the butterfly fauna into insular districts in which many
species survived, and whence they afterwards spread to other
parts.

Before we consider the land bridge problem from the point
of view of the marine fauna, some remarks on the general
character of the present mammalian fauna. of Alaska will
be of interest. Both Labrador and Newfoundland, the two
districts in the east which seem to have been little affected by
the Glacial drift, and on which the still existing mammalian
fauna probably survived from pre-Glacial times, were found
to contain a certain number of peculiar species. We should,
therefore, expect such a vast region as Alaska, which was
also scarcely affected by Glacial drift deposits, to contain
even a larger number of indigenous species of mammals that
survived the Ice Age in the country. We do not positively
know that any mammals survived the Ice Age in Alaska, but
since we are unacquainted with any reasons why they should
not have done so, that assumption is warrantable. The num-
ber of mammals peculiar to the country, is surprisingly large,
and this alone implies that these animals inhabited the
country for a sufficiently long time to develop characters
distinguishing them specifically from those of the neigh-
bouring parts in North America. The objection has been
raised that American naturalists hold somewhat narrower
views as to specific distinctions than are current among

* Standfuss, M., ‘‘ Palaearktische Gross-Schmetterlinge,”’ pp. 296—298.

99 ORIGIN OF LIFE IN AMERICA

European zoologists, and that many of their so-called species
are nothing more than varieties or races. In many cases this
criticism is not justified, but even if we regarded the forty-
five species of mammals peculiar to Alaska merely as varieties,
the fauna still retains a remarkably distinctive character which
can only have arisen through long-continued isolation. I
herewith give a list of the species of mammals confined to
Alaska. In doing so it must be understood that I am not com-
mitting myself to any opinion as to their specific distinet-
ness. |

Alces gigas. Evotomys wrangeli.
Rangifer montanus. Lemmus minusculus.
Oreamnos kennedyi. ~ » higripes.
Sciuropterus yukonensis. Fiber spatulatus,
Citellus osgoodi. Lepus othus.

: » nebulicola. » | poadromus.

» beringensis, Synaptomys wrangeli.

» barrowensis. r dalli.

» Stonii. Vulpes kenaiensis.
Microtus operarius. » pribilofensis.

Pr unalascensis. » beringensis.

¥ kadiacensis. Ursus middendorffi.

i yakutatensis. » kidderi.

es sitkensis. Hall,

5 innuitus. » eulophus,.

a abbreviatus. », kKenaiensis.
Ochotona collaris. » emmonsi.
Tamias caniceps. Mustela kenaiensis.
Peromyscus sitkensis. » arcticus.
Teonoma saxamans, Sorex tundrensis.
Evotomys dawsoni. » glacialis.

3 orca, » pribilofensis.

The late Professor Asa Gray was the first to draw attention
to the relationship of the flora of America and that of Asia.
Hie was struck particularly with the remarkable resemblance
of some of the plants found in the eastern United States to
those inhabiting Japan. This particular feature, however,
will be discussed in one of the subsequent chapters. It was
not till much more recently that botanists became acquainted
with the intimate floristic relationship between Alaska and

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MAMMALS PECULIAR TO ALASKA — 983

north-eastern Asia. Professor Engler * cites a large number
of arctic-alpine plants, most. of which are met with in these
two regions, and extend southward in America along the
Rocky Mountain chain. He argues that some of the species
were probably capable of spreading from the one continent
to the other under the existing conditions of land and water.
Of others he does not consider that they could have drifted
across the ocean by occasional means of transport, and he
urges that only a former land connection in the north could
satisfactorily explain their presence in Asia and North
America.

Finally a few observations on the land bridge problem from |
the marine faunal aspect may elucidate some doubtful points.

Dr. Dall+ divides the existing marine fauna of the north-

eastern Pacific into three zones, viz., the Oregonian, Aleutian
and Arctic. The Oregonian extends from Monterey to the
Shumagin Islands. The Aleutian passes westward from the
Shumagin Islands, includes the Aleutian chain, and reaches

_ morthward to the floating ice in Bering Sea, bounded by a

depth of five hundred fathoms. The arctic zone stretches
indefinitely southward beyond the five-hundred-fathom line,

_ and is bounded in the north by floating ice, or water of thirty-

two degrees. Some arctic species have crept southward to the
northern islands of Japan and Cape Newenham, while a series

_ of isolated arctic colonies occur from Cook’s Inlet southward
and eastward.

Dr. Dall’s views are mostly derived from a study of the

marine mollusca, and it is interesting to note that in the

main points they are confirmed by Miss Rathbun f after an

_ examination of the northern Pacific crustacea. She states
_ that arctic species often continue southward through Bering
Strait, along the west coast of Bering Sea, to Okhotsk Sea and

the Kurile Islands. Some of them extend eastward to Puget

- Sound and even further south. Miss Rathbun noticed that in
4 exceptional cases, for instance Philyra pisum and Cancer

* Engler, A., ‘‘ Entwicklungsgeschichte der nérdl. Florengebiete,”’

pp. 22—43.

+ Dall, W. H., ‘“‘ Marine Faunal Region of North Pacific,’’ p. 206. |
{ Rathbun, Mary J., ‘“‘ Decapod Crustaceans of North-West Coast,”

94 ORIGIN OF LIFE IN AMERICA

amphiaetus, Japanese species are found to occur in approxi-
mately the same latitude on the American coast, without
obvious connection by way of Alaska.

The Black Stream of Japan, the “ Kuroshiwo,” ‘competi
to the Gulf Stream of the Atlantic Ocean, keeps outside the
island chain of the east coast of Asia, skirts the Aleutian
Islands, and then makes itself felt on the south coast of
Alaska. The fish fauna of the northern Sea of Japan has
nineteen per cent. of species in common with the south coast
of Alaska. With the Bering Sea the latter has about twice
as many fishes in common. All of these are forms frequent-
ing cold seas.*

Dr. Dall+ recently expressed the opinion, based on a
study of Tertiary marine deposits, that the conditions indi-
cated by the faunas of the post-EHocene Tertiary on the Pacific¢
coast from Oregon northward are a cool temperate climate
in the early and middle Miocene, a warming up towards the
end of the Miocene, culminating in a decidedly more warm-
water fauna in the Pliocene, and a return to cold, if not prac-
tically arctic, temperature in the Pleistocene. Further south,
on the Californian coast, the Tertiary marine faunas, espe-
cially those of San Pedro, have been very carefully studied
by Professor R. Arnold. The Pliocene fauna, he remarks,
though not quite similar to the fauna at present living off
San Pedro, still contains many species which now only occur
north of that locality. Many of these northern species are
limited in range ‘to the boreal waters north of Puget Sound.
Hence he concludes that these Pliocene deposits were laid
down in water much colder than that now found off San Pedro.
In the lower ‘beds of the Pleistocene, he continues, the cold
climatic conditions prevalent during the later Pliocene were
giving place to a warmer climate, which had its effect on
the boreal species of San Pedro. Southern species gradually
increase in number ‘while northern ones become scarcer.
Finally the upper Pleistocene beds contain 142 per cent.

of species that are only now found living south of San Pedro,

* Schmidt, P., ‘‘ Verbreitung der Fische im Stillen Ocean,”’ p. 564.
+ Dall, W. H., ‘‘ Climatic Conditions at Nome,” p. 457.

NORTH PACIFIC MARINE FAUNA 95

while 6:1 per cent. at present occur exclusively north of
this locality. Professor Arnold* is thus led to the con-
clusion that semi-tropical conditions prevailed during the
aeposition of the Pleistocene formation. He also emphasises
the fact that the later Tertiary and Pleistocene faunas of
Japan and the west coast of the United States resembled one
another much more than the faunas of the two sides of the
Pacific do at the present time.

Nothing could be more contradictory than the two state-
ments of Dr. Dall and Professor Arnold as to the climatic
conditions prevailing in ‘two portions of the Pacific coast of
North America in Pliocene and Pleistocene times. It seems
almost as if the deposits from which Dr. Dall derived his con-
clusions were not contemporaneous with those that led Pro-
fessor Arnold to pronounce the views just stated. It is
scarcely possible to conceive that, while a warm-water fauna
existed on the Oregon and Alaskan coasts in Pliocene times,
California should have had a cold climate. Arctic conditions
are then supposed to have supervened on the north Pacific
coast. On the Californian coast, on the other hand, the cold
Pliocene climate is stated to have been succeeded by a semi-
tropical one during the Pleistocene Period.

It is now generally recognised, I think, that Central
America, in its present configuration, originated by a final
union of pre-existing independent land-masses in Pliocene
times. That an inter-oceanic current, now no longer exist-
ing, might have produced altogether peculiar climatic con-
ditions on the Californian coast in Miocene times but
not later seems admissible. If we suppose that the Japanese
“Kuroshiwo”’ current formerly sent part of its warm
waters through a wider opening at Bering Strait into the
Arctic Ocean, would it have had the effect of inducing
the Mexican fauna to advance northward and the arctic
fauna to pour southward towards the coast of Oregon ?
I doubt, even under such geographical conditions, whether
the Pleistocene faunas of California and Oregon could
have differed to such an extent as described by Dr. Dall and

* Arnold, Ralph, ‘‘ Marine Pliocene and Pleistocene of San Pedro,”
pp. 65—67,

96 ORIGIN OF LIFE IN AMERICA

Professor Arnold. At any rate, it is reasonable to infer that
a rise to a higher temperature of the northern Pacific Ocean,
coupled with an increased conveyance of Asiatic species to
the American coasts and a northward advance of southern
forms must have coincided with the closing of Bering Strait.
And it was not until Pliocene times, according to Professor
J.-P. Smith,* that the marine faunas of Japan and the western
coast of America began to be remarkably similar, many species
being identical. From this fact we must conclude that inter-
migration between the two continents had set along a northern
shore line. During the preceding Miocene Period the marine
fauna of California consisted of endemic species mixed with
southern and circumboreal ones, but without any Asiatic
admixture. Consequently there was probably a wide com-
munication between the Pacific and the Arctic Ocean, favour-
ing the entrance into the latter of a warm current which
profoundly affected the Arctic Regions. The curious relation-
ship to Pacific mollusks which is noticeable among some
forms of the English Crag deposits may possibly date from
this theoretical Miocene current, which may have carried
marine species right across the Polar Seas to Europe.

At the beginning of the Pleistocene Period, the same con-
ditions existed, according to Professor Smith, as in the Upper
Pliocene. As the waters of the Californian coast gradually
became warmer, he remarks, Mexican species began to creep
northward. But this, he says, does not mean that connection
with Japan was cut off. The continuation of the conditions
that permitted Japanese species to migrate to California,
merely allowed marine animals to:.make their way up the.
American coast also. Here I must beg to differ from Pro-
fessor Smith. If a change in the fauna of the upper Pleis-
tocene of California took place as asserted, that change was
in all probability due to a gradual sinking of the land in
the north, for a moderate subsidence in northern Alaska at
any rate has been recorded by Dr. Dall ¢ during later Pleisto-
cene times. A gradual modification was thus brought about
in the disposition of land and water, the continents of Asia
and North America slowly assuming their present shapes.

* Smith, J. P., ‘‘ Periodic Migrations,” pp. 225—226.
+ Dall, W. H., ‘“‘ Neocene of North America,” p. 278,

NORTHERN PACIFIC IN THE PAST 97

I have endeavoured to show in this chapter how the more
striking instances of relationship among the animals of Asia
and North America can be explained, how they arose and
under what climatic conditions. That Alaska was once joined
by land to the opposite shore of Asia has been almost uni-
versally acknowledged by biologists and geologists. But for
our purpose we required something more definite than a state-
ment such as that of Professor Heilprin,* “ it appears likely
that the bears, swine, oxen, sheep, antelopes and elephants
originated in the Old World, whence they were transplanted,
by way of some land connection existing in the north, into
the New World.’’ Even Dr. Arldt’s + remark, “the bridge
between Asia and North America remained until the Glacial
Period,” is too vague. I think I have brought together suffi-
cient data to show that a land connection existed in the
region of Bering Strait during Pliocene times until the com-
mencement, or perhaps until the end, of the early part of the
Pleistocene Period. As far as I know, the only fact that can be
_ brought forward against such an assumption is the discovery
_ by Dr. Dall { of marine gravels at Nome, in Alaska, contain-
_ ing shells which he believed to be of Pliocene Age. Consider-
ing, on the other hand, that the gravels in question only con-
tained one distinct species, it is quite possible that they may
_ not be so old as Dr. Dall thinks. And even if their Pliocene
' age should be established by further researches, it only proves
- that the land connection was not so wide as we are apt to
believe. These gravels do not disprove the existence of the
_ land bridge, for Nome is situated to the south of Bering Strait
_ on the shores of the Bering Sea.

_ I have adduced testimony showing that Alaska, not only in
_ Pliocene times, but also during part of the Pleistocene Period,

had a comparatively mild climate. Many of the larger
| Mammals seem to have become exterminated within more
_ recent times owing to a change of climate. There is no indi-
_ cation of any wholesale destruction of the fauna during the
Glacial Epoch followed by a recent introduction from the

* Heilprin, A., ‘‘ Geographical Distribution of Animals,” p. 179.
+ Arldt, Th., ‘‘ Entwicklung der Kontinente,”’ p. 293.

{ Dall, W. H., ‘ Climatic Conditions at Nome,” p 457.

L.A. H

, ot
98 ORIGIN OF LIFE IN AMERICA

south. If such an event had happened we should not have had
such a large percentage of peculiar forms of animal life in
Alaska, and more southern forms ought to have found their
way there, such as the American deer and many others.

It would seem, therefore, as if both the Atlantic and the
Pacific Ocean became closed in the north simultaneously and.
remained so for a considerable time (Fig. 7). The southern
shores of both the great land bridges were then under the direct
influence of warm ocean ‘currents resulting in favourable con-
ditions for the growth of vegetation and the food supply
for large mammals. The northern shores of the land
bridges, on the other hand, were in immediate contact
with a closed Arctic Ocean, whose waters would naturally
have remained frozen for the greater part of the year.
During winter the snowfall all round the northern Atlantic
and northern Pacific Oceans was probably considerable.
The land being, moreover, at a higher level, this would
have resulted in the production of.local glaciers. Marine
transgressions from the Arctic Ocean then seem to have
taken place across northern Russia, as I described in my
work on the History of the European Fauna,* and across
the lowlands of arctic Canada as indicated on pp. 46—49.
My views on the Glacial Epoch and its nature are thus at
variance with those held by most geologists of the present
time. They agree with those put forward by Sir William
Dawson, and are more in accordance with the current
opinions at the time when the Glacial Epoch was spoken of
as the “ Diluvial Age.”

It is very generally believed, as I mentioned before, that the
climate in northern Kurope and northern North America was
very cold, and that all that vast region which is covered by
the deposit known as “ Glacial drift ” had been invaded during
the Glacial Epoch by thick masses of land ice, so as to destroy
practically: all life or drive it far southward of the southern
limits of the drift. I stated in another chapter (p. 77) that I
did not intend to make a special point in discussing the origin
of the Glacial Hpoch. I only incidentally bring forward a

* Scharff, R. F., ‘‘ History of European Fauna,” p. 172—184.
+ Dawson, W., ‘‘ Ice Age in Canada.”

Fia. 7.—Map of Northern portion of Northern Hemisphere, with supposed land
connections in early part of Glacial Epoch (shaded) and extent of sea (white).

[ Lo face p. 98.

1A Le ae
12m

3
.

2

y:
~

BERING STRAIT LAND BRIDGE 99

_ theory of its origin and nature which appear to me to agree
better with the geological history of the boreal fauna and flora,
as far as we are able to ascertain them, than the hypotheses
which have been so widely accepted by scientific men.
Professor Shaler * reminds us that the extension of rela-
tively warm climates which has occurred at certain stages
of the Earth’s history is perhaps explicable in an equally
simple manner as that of the Glacial Epoch. He expresses
the belief that if Bering Strait were as readily open to the
warm stream of the Pacific or “ Kuroshiwo ” as the Atlantic
is open to the Gulf Stream, the temperature of the region about
the North Pole would be lifted by at least thirty degrees above
its present mean annual. Indeed, if the Glacial Epoch had
been due to a simultaneous closing of the Arctic Ocean to the
genial influences of both Atlantic and Pacific, a mild climate
all over the Arctic Regions must have coincided with a more
copious flow of the “ Kuroshiwo ” into the Arctic Ocean. And
here apparently lies the great stumbling block to my theory

_ on the origin of the Glacial Epoch. If the warmer tempera-

_ ture in the Arctic Regions in Miocene and Oligocene times
had been due to a wider Bering Strait, and, consequently, to
the fact that a greater volume of the “ Kuroshiwo”. then
poured into the Arctic Ocean, how are we to account for the
_ faunistic affinities existing between Asia and North America
_ during this part of the Tertiary Era? There are numbers of
animals in North America which have an Asiatic ancestry, but
_ could not have entered the Continent with the great invasion
_ that I described as crossing the Bering Strait land bridge.
_ These and many other facts point to the existence of a land
_ bridge between Asia and North America in early Tertiary.
_ times. All the same, several important features imply that
before the Pliocene Period the ‘‘ Kuroshiwo ”’ really sent its
warm waters altogether to the Arctic Ocean.

As I mentioned above, no Japanese affinities are recognis-
able in the American Miocene marine fauna. On the other
hand, there is some evidence that the Miocene floras of
Sakhalin and Japan were intimately related to the Miocene
flora of North America. These apparently contradictory

* Shaler, N.8., ‘‘ Nature and Man in America,” p. 143.
H 2

100 ORIGIN OF LIFE IN AMERICA

evidences can only be due to the fact that a portion of the
Pacific coast of North America was connected by land in Mio-
cene times with Sakhalin and Japan, whereas the “ Kuro-
shiwo ”’ flowed northward between these islands and the main-
land of Asia. In the subsequent chapters the evidence which
has led me to these conclusions will be more fully dealt with.

CHAPTER V

THE ROCKY MOUNTAINS

From Alaska we retrace our steps to Canada, by that magni-
ficient mountain range popularly known as the “ Rockies.”
I have already mentioned that the Rocky Mountains prac-
tically end near the shores of the Arctic Ocean. They begin
in northern Mexico. Although we can approximately fix
the beginning and end of this vast range of mountains and
even its eastern border, the western boundaries are more
vague and indefinite. In British Columbia, which is so famed |
for its grand and impressive scenery, its rugged mountains
and great forests, the northern spurs of the Cascade Moun-
tains appear to merge into the Rockies, so that it becomes a
_ matter of some difficulty to discriminate clearly between the

_ two. Further south the Rocky Mountains cross the high
_ plateau of Wyoming, sometimes spoken of as the “ Laramie
region.” We also meet here the complex mountain groups to
which the name of ‘“ Stony Mountains” has been applied.
_ South of the plateau the mountains again grow more irregular
and lofty than to the north of it. Another great plateau covers
_ part of southern Utah, western Colorado, New Mexico and
_ northern Arizona. With a height of over 6,000 feet above
_ 8ea-level, this region has suffered great erosion, and is deeply
_ trenched by fantastic gorges which intersect it in every direc-

tion. The most famous of them, the Colorado Cafion, is a
_ clean-cut chasm, which, in the course of ages, has been slowly
_ carved by the river to the stupendous depth of 6,000 feet
in the horizontal strata.

It is not only the lover of scenery, but particularly the
- haturalist and palaeontologist who appreciate the unrivalled
attractions of the Rocky Mountains. These mountains, more

over, have been the direct means of exposing what are probably

Teas

se

fy

102 ORIGIN OF LIFE IN AMERICA

the most valuable and extensive deposits of fossils in
existence.*

As we enter the United States, proceeding along the Rocky
Mountains, we soon find ourselves in the midst of the Miocene
and the lower Oligocene beds (White River) of Montana.
Further south, in Wyoming, we come to the Wind River beds,
while on our left to the éast lie the Wasatch deposits, both
of which belong to the lower Eocene. Westward we cross
into the middle HKocene Bridger and Washakie beds of
Wyoming, and also the upper Eocene Uinta of Utah. Much
further south we finally meet with the famous Puerco, Tor-
rejon and Wasatch formations of the San Juan basin in New
Mexico, which are held to be of basal and lower Hocene age.
Owing to the labours chiefly of Leidy, Marsh, Cope, Scott,
Osborn, Wortman, Matthew, Hatcher, and others, a most re-
markable assemblage of fossils has been obtained among these
immensely rich deposits. Our knowledge of the former
inhabitants of North America has thus greatly increased
within recent years, and has aided us in tracing the gradual
changes of land and water that the continent has undergone
in past times. Great efforts are now being made to work out
the correlation of the North American mammal-bearing
horizons. I propose to return to this subject later on, and
need not dwell on it any longer at present.

Although glaciers have now almost entirely disappeared
from the Rocky Mountains, abundant proofs have been left
of their past presence in the shape of moraines, and polished
as well as striated surfaces. These signs of former glaciation
are very different from the thick mantle of drift that we
noticed in Canada, and which is likewise attributed to the
action of glaciers. Only the highest summits and the most
elevated valleys of the Rocky Mountains were ever occupied
by ice, and there does not appear to be any sign of a deposit
in the whole range resembling the northern drift.

These glaciers, no doubt, owed their existence to a greatly
increased precipitation of moisture in the Rocky Mountains
during the Ice Age, for we possess quite an unmistakable

* Russell, I. C., ‘‘ North America,” pp. 122—136.
+ Whitney, J. D.,. “ Climatic Changes,” pp. 64—72.

GREAT SALT LAKE BASIN 103

record of a past humid period in the basin of the Great Salt
Lake in Utah. All round the present lake we find a most
interesting series of terraces at varying heights, which clearly
represent ancient shore-lines. It has thus been established
that in Pleistocene times, during its greatest development,
the lake had the enormous area of more than 19,000 square
miles, that is, nearly the size of Lake Michigan, with a depth
of about 1,000 feet. This ancient ‘“ Lake Bonneville,” as it
has been called, has since been greatly reduced in size by the
slowly increasing aridity of the country. Its diminutive
descendant, the Great Salt Lake, is rapidly drying up, it
average depth being only twenty feet. Other large fresh-water
lakes existed in the Great Basin during the Glacial Epoch.
Sometimes it is customary to include the western Sierra
Nevada and Cascade Mountains under the term “ Rocky
Mountains.” Asa Gray and Sir Joseph Hooker have even
added to this area that of the Great Basin in their account
of the Rocky Mountain flora. More recently the distinctive-
ness of these two mountain systems is being more generally
recognised. The forests of the Rocky Mountains are dis-
tinguished from those of the eastern States by the prevalence
of the pyramidal evergreen conifers, whereas in the east the
trees are round-headed and mostly deciduous. The endemic
flora, consisting of thirty-three per cent. of all thé plants
found in the Rocky Mountains, forms a prominent element.*
We have noticed that some of the alpine plants inhabiting
the White Mountains are unknown in western America, for
instance, Diapensia lapponica and Loiseleuria procumbens.
On the other hand, a large number of the alpine Rocky Moun-
tain species do not occur in the east, whereas a few, such as
Rhododendron lapponicum, Arctostaphylos alpina, Rubus
chamaemorus and Veronica alpina, are common to both, point-
ing to the great antiquity of this element in the flora.+
Many of the plants occur also in Asia; others are closely
related to arctic-alpine species. Most of the endemic element
of the Rocky Mountain flora has clearly been derived from {hat

* Gray, A., and J. D. Hooker, ‘‘ Vegetation des Rocky Mountain
Gebietes,” p. 267.

+ Rydberg, P. A., “Composition of Rocky Mountain Flora,” p. 870.

104 ORIGIN OF LIFE IN AMERICA

of the lower slopes of the mountains, and to it belong the
typically American alpine species. They reach their greatest
development in the southern portion of the Rockies.

One of the most remarkable features, which I shall have
occasion to draw attention to again in another chapter, is the
occurrence in the Rocky Mountains of some species of plants,
which reappear in the southern Andes, without being repre-
sented either in the Mexican highlands or in the tropical
Andes. Among these, Professor Engler* mentions the
dwarf gentian (Gentiana prostrata), the mealy primrose
(Primula farinosa), the hoary draba (Draba incana) and
the alpine foxtail (Alopecurus alpinus). All these are
common well-known Huropean species. A few more’ have
since been added by Professor Bray t+ This small group
of species is of peculiar interest, not only because some-
what analogous instances of distribution occur among insects,
but also because this feature is by no means limited to
mountain forms. In another chapter I shall allude to .a
number of species inhabiting the arid regions of south-
western North America that likewise are quite unknown in the
moist tropical and sub-tropical belts of country to the south,
yet reappear in the extreme south of South America. Whether
all these species possess particular facilities for dispersal
over wide areas or whether former conditions of land and
water were more suitable than they are at present for dis-
persal will be discussed later on (p. 414).

The fauna of the Rocky Mountains resembles the flora in
its composition, except that among the higher animals, at any,
rate, the species are almost all endemic. Two kinds of animals
in particular are associated with the Rocky Mountains in
sportsmen’s minds, namely, the mountain sheep, or big-horn,
and the Rocky Mountain goat. The former used to be known
as Ovis canadensis. But from the systematic mill of the
zoologist, as Dr. A. E. Brown { puts it, have been produced —
seven new species and sub-species, all very closely re-
lated to one another. As already stated, the Kamchatkan

* Engler, A., ‘“ Entwicklungsgeschichte,” II., p. 256.
+ Bray, W. L., “ Relations of North American Flora,” p. 713.
{ Brown, A. E., ‘‘ Zoology of North American Big Game,” p, 69,

RAPE GE SITY SE Fae ae

- : c= ~ er
oS eet
So ee ee

AMERICAN MOUNTAIN SHEEP 105

sheep (Ovis nivicola) is more nearly akin to the American
sheep than it is to other Asiatic ones, and the occurrence

‘on both sides of Bering Strait of such near relations

forms one of the strongest buttresses for the belief in
a geologically recent land connection between Asia and
North America in the neighbourhood of Bering Sea. The
various forms of American sheep are entirely confined to the
western mountain region, where they are found from the
Alaska mountains to the mountains on the long peninsula
of Lower California, and eastward as far as Yellowstone Park.
The home of the big-horn is the loftiest rim-rock of the high
mountain plateaux, or the most rugged and forbidding bad-
lands of the middle altitudes. In summer, says Dr. Horna-
day,* its favourite pastures are the treeless slopes above the
timber-line, and in winter it paws through the snows of the
mountain meadows to reach the tallest spears of grass. When
the raging storms and deep snows of winter drive the elk and
deer down into the villages for food and shelter, the mountain
sheep makes no perceptible change in its habitat. Its agility
is nothing short of marvellous, and, from its wariness and diffi-
culty of approach, it is a favourite object of pursuit of the
experienced hunter.

If, as it seems likely, the American mountain sheep has
entered North America from north-eastern Asia within recent
geological times, the fact of its having spread to Lower Cali-
fornia and developed several distinct forms is an argument
in favour of a pre-Glacial immigration. That sheep had
already penetrated to North America in Pliocene times is
also proved by the discovery of the horn cores of a sheep
(Ovis scaphoceras) in northern Nicaragua.}

The comparatively dull-witted Rocky Mountain goat (Ore-

-amnos montanus) shares with the big-horn the almost inae-

cessible peaks and ridges of the Rocky Mountains, but, being

clumsy and slow, it rarely ventures far from its usual haunts.

Unlike the sheep, the Rocky Mountain goat has a very local

and discontinuous range.{ It seems almost as if its original

home had been in the coast ranges of Oregon and Washington,
* Hornaday, W. T., ‘ Notes on the Mountain Sheep,” p. 7%

+ Lucas, F. A., ‘‘ Fossil Bison of North America,” p. 756.
} Grant, Madison, ‘‘The Rocky Mountain Goat,” p. 9.

106 ORIGIN OF LIFE IN AMERICA

and that it had then spread northward to British Columbia
and southern Alaska, and eastward to the Rocky Mountains.
Its whole distribution is thus confined to the north-western
United States and western Canada. The term “ goat” is really
a@ misnomer. It is not a true goat, nor yet a true antelope.
We might with more justification call it a “ goat-antelope.”

In some respects it resembles the European chamois
(Rupicapra), in others the serow and goral (Nemorrhaedus)
and the takin (Budorcas). The last three are confined to Asia,
and all of them, though generically distinct from the Rocky
Mountain goat, belong to the same group of goat-antelopes.

A species of Nemorrhaedus occurs in the mountains of
Japan and northern China, and we might, with Dr. Brown,
be tempted to assume that Oreamnos has arisen in America
from some Pleistocene immigrant of the genus Nemor-
rhaedus.* But surely the genus Oreamnos, to which the
Rocky Mountain goat belongs, must be a very ancient one.
' The peculiar discontinuous range of the whole group implies
antiquity. The remains of the mountain goat have been dis-
covered in Potter Creek Cave of California, while Mr. Cragin
is said to have described a fossil species of Nemorrhaedus
from the Pleistocene of Colorado. I have not been able to
trace the description or further particulars. At any rate,
the more remote origin of Oreamnos is shrouded in obscurity.
We certainly have no definite evidence that its ancestors came
from Asia in Pleistocene times. They probably reached the
continent much earlier.

The Rocky Mountain goat occasionally falls a victim to the
cougar or puma, better known in the west as the “ mountain
lion,” which, like its prey, is a typically American animal.
From a distributional point of view it is one of the most
remarkable mammals, as it exceeds all others in the great
extent of its range. Its utter indifference to climatic condi-
tions is shown by its occurrence from southern Patagonia
right through the tropics to western Canada. It flourishes
from the plains of Florida to the regions of the permanent

snows in the Rockies and Andes. It is true that those who
take note of small differences no longer believe in one species

* Brown, A. E., “ North American Big Game,” p. 75.

oe

oe eee a De Pale ee VO
re a am, * is

7 SOD Re a ie

ROCKY MOUNTAIN GOAT 107

possessing this vast range. Like almost all other mammals,
the cougar (Felis concolor), which in all its essential habits
and traits remains the same, whether living in mountain,
open plain or forest, under arctic cold or tropical heat, has
yet been split up into several distinct species.

The nearest Old World relations of the cougar are the lion
and tiger, both of which differ from it very strikingly in size,
habit and colour. It is perfectly obvious, therefore, that it
is not a geologically recent immigrant from Asia. ‘Two very
closely allied species of large cats, moreover, have been dis-
covered in Pleistocene deposits in Argentina; while the
cougar itself has left its remains, along with those of extinct
members of the cat tribe, in the Conard Fissure. Another
large cat (Felis hillianus) has been found fossil by Professor
Cope in the Blanco formation of Texas, this being now looked
upon as middle Pliocene. Hence it is probable that the
ancestors of the cougar already flourished in North America
as well as in the southern continent in Pliocene times. The
facts of its recent distribution seem to point to its having
entered North America from the south, and it may pos-
sibly have done so in Pliocene times when the northern
continent became definitely connected with South America.
Further details as to its early history are still lacking.

As we descend the mountains through the forest belt and
finally reach the foot-hills, we meet with two large ungulates
whose acquaintance we have not hitherto had an opportunity
of making. Both of these are confined to the western States,
and are well known to the hunters of the Rocky Mountain
region. The black-tail, or mule deer (Odocoileus hemionus),

as it is often called on account of its big prominent ears,.

seems at first sight not to be very different from the American
elk or wapiti, except in size. But the latter belongs to quite
a different genus. If we examine the antlers of the two more
carefully, we notice that the brow tines are lacking in the
mule deer. There are also distinctions in the skull, while
the lower parts of the metacarpal bones of the front limbs
are retained in the mule deer. The wapiti deer is descended
from an Old World stock which, as I explained (p. 68),
crossed. over from Asia by a land bridge in Pliocene or early
Pleistocene: times. : In it only the upper metacarpals remain,

° *

108 ORIGIN OF LIFE IN AMERICA

and it differs in other fundamental characters from the mule
deer, which has apparently no near relations in the Old ‘World,
and which we may justly call the true American deer.

Fossil remains of the mule-deer have been found in the
Conard Fissure.* The fossil bones of other deer from the

Pleistocene of Illinois, Iowa, Wisconsin and Indiana, have:

been referred to extinct species of the genus Odocoileus to
which the mule-deer belongs. No Pliocene or older traces
of this genus have as yet been discovered in North America,
if we adopt the generally accepted view of the Conard Fissure
being of Pleistocene age. Altogether there are three fairly
distinct species of the type of the mule-deer in North America,
namely the one I have just described, the white-tailed deer
(Odocoileus virginianus) and the black-tailed Columbian deer
(O. columbianus).

It is of considerable interest to know that this genus lives
not only in Central America, but right to the southern ex-
tremity of South America in Chile. ‘This fact alone is remark-
able, for nowhere else in the world are deer found south of the
Equator. They are entirely absent from Africa and Australia.
However, it is by no means the only noteworthy circumstance
about this American group of deer. Those who are ac-
quainted with the habits and life history of the deer tribe
know that the young of deer with large branching antlers
at first possess no antlers. Afterwards small, simple and
unbranched processes appear on their heads. From year
to year they are shed and new ones take their place, and these
are always a little more complex than the previous ones. The
gradual development of the race seems to follow that of the
individual. It is only in the more recent geological periods
that deer with branching antlers make their appearance. As
we go back to earlier deposits the deer skulls only bear simple
antlers with one or two branches. In still older strata we
meet with deer that were devoid of antlers, while they gene-
rally possessed long canine teeth which no doubt were useful
as organs of defence. It has been rightly argued that the
complex antlers have only been developed in comparatively
recent geological times, and that deer with simple antlers

* Brown, Barnum, ‘‘ Conard Fissure,” p. 205,

— se

—

AMERICAN MULE DEER 109

which we find living here and there in isolated districts, are
more ancient in point of origin.

In South America we have still living at the present
moment deer of the type of the mule-deer, only smaller,
with simple forked antlers. Other still smaller deer possess
merely minute spike-antlers. Extinct deer, moreover, with all
the different kinds of antlers, have been observed in South
American Pleistocene and Pliocene deposits. One species
(Odocoileus avius), which, according to Professor Ameghino,
belongs to the group with complex antlers, has even been
noticed in the upper Miocene of Argentina.

Both fossil and recent evidence thus clearly points to South
America as the source of these true American deer. If we
supposed that the ancestors of the North American species
of Odocoileus had penetrated northward in Pliocene times,
when Central America assumed its present shape, we should
have a reasonable explanation for the fact that the genus
has never spread to the peninsula of Alaska, nor into north-
eastern Canada and Newfoundland.

What prevents the general adoption of the theory of the
South American origin of this group of deer? Clearly the
fact that while the deer family (Cervidae) is represented
from the Oligocene to the most recent deposits in Europe,
it only makes its appearance in South America in the upper
Miocene. ‘The original home of the family is therefore
believed to be in the northern hemisphere, and this assump-
tion is strengthened by the circumstance that nowhere except
in South America have deer penetrated to the southern hemis-
phere. Since it is inadmissible to argue that mammals so }
near akin as the Old World and New World deer should have
appeared quite independently of one another in two distinct
centres, these affinities can only be explained by migration
from the one centre to the other. According to most palaeonto-
logists who expressed an opinion on this problem, the South
American.deer could only, for the reasons stated, have entered
South America from North America. Whether they were
developed in the Old World or the New, it is evident, remarks

_ Mr. Lydekker,* that the American deer originated in the

* Lydekker, R., ‘‘ Deer of all Lands,”’ p. 245.

110 ORIGIN OF LIFE IN AMERICA

northern hemisphere, and that they are comparatively modern
immigrants into South America, where they now attain their
maximum development.

Mr. Lydekker gets over the difficulty of the simple-antlered
South American deer, or brockets as they are called, by the
admission that because they are unknown in North America,
they are not ancestral forms. ‘He thinks they should be
regarded as degraded or arrested types of the group (p. 296).

Professor Marsh * was inclined to look upon the North
American Leptomeryx as the probable progenitor of the
Cervidae. His suggestion led to further researches on the
part of Dr. Matthew} who supplied a connecting link in the
chain of ancestry of Odocoileus in the Miocene Blastomeryx.
That Dr. Matthew’s view, however, is not generally accepted
may be gathered from Professor Osborn’s { recent remark in
reference to the Pleistocene Period in North America, that
among the newly entering northern forms are Odocoileus,
Ursus and Erethizon. Professor Osborn’s § opinion is that
the origin of the Cervidae will probably prove to be Asiatic.
I quite concur in the view that they are of Old World origin,
and yet I hold that the ancestors of the North American
Odocoileus have invaded the northern continent from South
America. The remote ancestors of Odocoileus must, there-
fore, have penetrated from the Old World to South America
without attaining North America. How they have done so is
the problem I shall endeavour to solve.

_ Later on, when we come to deal with the zoogeographical
relationship of South America and Africa, I shall show that.
we possess valuable evidence for the belief in a former land
connection across the southern Atlantic between these conti-
nents. This, however, will not help us in explaining the deer
problem, because no deer have ever been found fossil in Africa
south of the Sahara, and those species which have succeeded in
establishing themselves in northern Africa have clearly done
so in recent geological times. Deer are absent from all the

* Marsh, O. C., “ Introduction of Vertebrate Life in America,”’ p. 36.
Tt Matthew, W. D., “‘Osteology of Blastomeryx,” p. 535. tia
} Osborn, H. F., ‘‘ Cenozoic Mammal Horizons,” p. 88.

§ Osborn, H. F., ‘Ten Years Progress in Palaeontology,” p. 107.

L

ORIGIN OF AMERICAN DEER 111

remainder of the continent. On the other hand, there is living
in Europe and Asia at the present time a genus of. deer
(Capreolus) which has several important characters in
common with Odocoileus and its more primitive South
American relations. The genus Capreolus, which includes
the roedeer, is distinguished from all the other Old World
deer in its tele-metacarpal front limbs, that is to say in the
possession of the lower remnants of the lateral metacarpal
bones. It resembles, as we already know, in this character
the true Americdn deer. Moreover, as Mr. Rorig* has
pointed out, this is not the only feature of resemblance be-
tween Capreolus and Odocoileus. The antlers of the former
likewise agree with those of the New World deer, rather than
with those of the Old World. Capreolus has the backwardly
directed tine of Odocoileus, and lacks the brow tine of Cervus.
Even in the period of renewal of the antlers, the roedeer
agrees with the American deer, this change taking place in
the winter months, while it occurs in all the other Old World
deer in the spring and summer. Only three kinds of roedeer
exist at present. In Miocene and Pliocene times, however,
France and Germany were tenanted by quite a large
assemblage of tele-metacarpal deer, all of which lacked the
brow tine like Capreolus. The earlier history of these deer
is largely obscured by the circumstance that only fragmen-
tary parts of the skeleton are known. Thus the Miocene
species of Dicrocerus, which is supposed to be related to the
living Cervulus, possessed antlers that can be almost matched
by some of the recent South American mountain forms of
Odocoileus, whereas other South American forms (Blasto-
cerus) remind, one of the modern roebuck.+

I venture to think that all the deer of South America have
originated from one or more ancestors which invaded that
continent direct from western Europe in early Tertiary times.
Although it is true that we possess little palaeontological evi-
dence in support of such a theory, a land connection must
then have joined Europe with South America. The prob-
able period of this migration from Europe to South America,

* Rorig, Ad., ‘‘ Wachstum des Geweihes,”’ p. 424.
{ Rorig, Ad., ‘* Phylogenie des Cervidengeweihes,”’ p. 542.

=

112 ORIGIN OF LIFE IN AMERICA

as well as the nature of the land bridge which enabled the
deer to reach western America rather than the east, will be
discussed in one of the subsequent chapters. Some of the
more primitive forms still survive in South America, where
they have now been pressed into the mountain regions. The
newer and more vigorous types must have passed into North
America as soon as that continent became definitely connected
with South America in later Tertiary times.

In speaking of the western North American fauna, Pro-
fessor Osborn * tells us that in middle Miocene the peculiarly
. American Hypertragulidae disappeared, while the Huropean
Cervidae and the distinctly American Merycodontinae took
their place. Professor Osborn alludes no doubt to Palaeo-
meryx and Blastomeryx which seem to have originated in
southern Europe, and spread subsequently eastward to India
and onward to America. Both apparently became extinct in
North America before the advent of Odocoileus from the
south.

The other large hoofed animal I alluded to as frequenting
the lower slopes of the Rocky Mountains is one of the most
peculiar creatures in existence. It is so different from other
animals that it occupies the exclusive position of being the
solitary member of a distinct family. Known among z00-
logists as the “‘prong-horn”’ (Antilocapra americana), and
among hunters as the “antelope,” this splendid animal
possesses the graceful movements of the latter, while its horns
have a superficial resemblance to the antlers of a deer. There
is not the least real likeness, however, between the antlers
of the prong-horn and those of a deer, for they are not solid,
but hollow like the horns of a goat. The horn-sheaths,
like the antlers of a deer, are shed and reproduced at regular
intervals. The prong-horn ranges from eastern Mexico to
Saskatchewan in Canada and from the Missouri River in the
east to the Cascade Mountains of Oregon in the west. Hence
it is now a peculiarly western species, while it had crossed
the Mississippi during the* Pleistocene Period, and roamed
about Illinois and Wisconsin. The closely-allied extinct
genus Merycodus (Cosoryx) made its first appearance in the

* Osborn, H. F., ‘‘ Cenozoic Mammal Horizons,” p. 77,

EE ee

eS died

oo | = a

PRONG-HORN ANTELOPE 118

“Deep River” deposits of Montana in middle or lower

Miocene, and persisted until the Pliocene. During the latter
period several new genera, viz.: Capromeryx, Platatherium
and Leptotherium, branched off from the ancestral stock, and
made their way into newly-opened areas. The last two have
occurred in recent beds in Brazil, the other in Nebraska.
Thus the family Antilocapridae to which the recent prong-
horn and all these fossils belong, originated in América and
never left it.

Among the birds of the Rocky Mountains the dippers are
very characteristic. They are quite unrepresented on any
of the eastern mountain systems, being also absent from
Greenland and Labrador. In the Old World they are more
or less confined to the mountains, but not nearly to the same
extent as in America. In my “ European Animals ”* I have
already cited Dr. Stejneger’s interesting article on the geo-

graphical distribution of the dippers (Cinclus), and I may

again briefly summarise the results of his studies. He places
the origin of the genus on the great plateau adjoining
northern India. At the dawn of the Tertiary Era the species
radiated from this centre east and west. America being then
connected by land with northern Asia, the ancestors of the
present dippers had special facilities for crossing to the New
World from Asia. They are supposed to have spread since
along the Rocky Mountains and Andes to the very furthest
end of South America. Dr. Stejneger’s theory} certainly ex-
plains the existing range of Cinclus in a satisfactory manner,
but there seems to me still another view of looking at the
problem. If, as I believe, the Atlantic Ocean was bridged
over by land in the direction of southern Europe in early.
Tertiary times, it is possible that the dippers may have been
introduced into the New World in that manner. At any rate,
the problem is worth considering from that point of view,
when the dippers come to be worked out in a, thoroughly
Systematic way. Among the older forms of both animals and
plants there are in western America a surprisingly large

number of groups which are closely related to European ones.

* Scharff, R. F., ‘‘ European Animals,” p. 200.
T Stejneger, L., ‘‘ Geographical Distribution of Cinclus,” p. 425.
L.A. I

114 ORIGIN OF LIFE IN AMERICA

In a later chapter I shall mention many of these. I would
only here draw attention to a striking botanical example
which seems to me due to direct migration from Europe to
western North America and not by way of Bering Strait.

Anemones are so much cultivated now in gardens that
almost everyone is familiar with them. Their geological
history no doubt has been a very remarkable one. Not a
single fossil anemone is known to science, because the plant
contains no part that might readily be preserved, and yet it
can be asserted that the genus must have originated in very
remote times. The occurrence of many species in isolated
mountain regions, the extremely discontinuous and wide
range of others, and especially the high percentage of
endemism, clearly imply that we have to deal with an ancient
genus. Dr, Ulbrich,* to whom we are indebted for a splendid
monograph of the genus Anemone, is of opinion that some
of its sections were already developed in early Tertiary times.
His view is, of course, entirely derived from what we might
call circumstantial evidence, just as Dr. Stejneger’s was in
regard to the age of the genus Cinclus. One of these species
of anemone (A. baldensis), a well-known alpine plant, is,
according to Dr. Ulbrich, probably of Miocene age. It grows
also in the Carpathians, the Apennines, the Pyrenees and
northern Spanish Mountains, but nowhere in Asia. Never-
theless, the same species occurs in the highest elevations of
the Sierra Nevada in California, in the Cascade and Rocky
Mountains. A very closely-allied form of anemone (A. teto-
nensis) lives at a height of over 10,000 feet in Idaho, and
another (A. jamesoni) at about the same elevation in the
Andes of Ecuador. All these nearly related forms, there-
fore, are confined to Europe and western America.

Among all the older American forms both of animals
and plants, other possible routes of migration besides the
Bering Strait one have to be taken into consideration. Re-
turning to the birds again, it seems to me that the genus
Regulus to which the European golden-crested wren belongs,
must have entered North America in Pliocene times along
with the great mammals alluded to in the last chapter. In

* Ulbrich, E., ‘‘ Geograph. Verbreitung d. Gattung Anemone,” p. 325.

et he nt Pew i b> 2

ROCKY MOUNTAIN PLANTS © 115

North America we have Regulus cuvieri, only one specimen
of which is known, Regulus satrapa and Regulus calendula.
None of these have succeeded in penetrating southward
beyond Guatemala in Central America, the genus having a
wide range on the continent. Hence it is reasonable to
suppose that the ancestors of Regulus invaded North America
from Asia by way of the Bering Strait land connection.
Among the invertebrates of the Rocky Mountains the
beetles and butterflies are probably the best-known groups.
They may be considered by some as of little importance in the
solution of such problems as we have been dealing ‘with,
because these insects are generally believed to be very lable
to accidental dispersal. One of the most powerful distri-
buting agents of insects subject to accidental dispersal is no
doubt the wind. Nevertheless many naturalists, who have
made a serious study of the geographical distribution of
animals and plants, have come to the conclusion that neither
wind nor other agencies of accidental dispersal are of such
paramount importance as we are often led to believe. The
species of a genus, even of butterflies or beetles, as a rule,
are clustered round a centre from which we can easily
imagine them to have been slowly dispersed in the course
of time. Usually we can trace an intimate relationship
between the species whose areas of distribution adjoin
one another. The conditions of dispersal, in fact, even
among winged insects, must be quite similar to those
with which we are acquainted among the higher mam-
mals. The latter spread gradually on land from their
centre of origin. Sometimes we meet with allied groups
of species among beetles and butterflies whose ranges are
separated by extremely wide areas in which no near relations
occur. We might be tempted to attribute such instances to
accidental dispersal by wind. We might suppose that an
exceptionally powerful storm had carried these frail insects
a few thousand miles away to a spot, where on alighting they
found the conditions for their future development favourable.
When similar cases of distribution occur among mammals
they are explained in a different manner. We then argue
that the related, but now widely separated or “ discontinuous,”
groups must long ago have had a perfectly continuous range

12

116 ORIGIN OF LIFE IN AMERICA

and that for some reason or other they have subsequently
been destroyed over wide areas, leaving at present only iso-
lated colonies. In some instances this theory of the origin
of discontinuous colonies of animals has been amply con-
firmed by fossil evidence. Camels, for example, or we might
say the family Camelidae to which they belong, are only
represented in South America and Asia; but since numerous
fossil members of the family occur in North America,
we possess decisive evidence that long ago the range of
the camel family was continuous. Discontinuity of range
among mammals is always looked upon by zoologists as
an unmistakable sign of antiquity. It is only when a
similar range occurs among the more easily dispersed in-
vertebrates and plants that naturalists are in the habit
of calling to aid exceptional forces of nature in explaining
their origin. The undoubted facility with which human
importations are scattered far and wide and become success-
fully established in districts remote from their original
home seems to encourage and invite speculations as to
the origin of discontinuously distributed invertebrates of
all kinds. Actual records of seeds, insects, snails, ete., sowed
broadcast by accidental agencies far from their native
land, appear to confirm the theories derived from successful
human transplantations. So much are these in vogue that
the ordinary and normal mode of dispersal is almost for-
gotten. Winds no doubt exert an influence in driving species
in the direction in which they blow. But many animals,
beasts as well as beetles or butterflies, possess the faculty
in a high degree of detecting the presence of their own kind
by the sense of smell. Winds would, and do, as we know,
convey scents from one animal to another, thus tending to
bring the sexes together. This has been very clearly estab-
lished by Mr. Webster.* The insect, being apprised by scent

of the presence of its own kind, would endeavour to travel —

in the direction contrary to that of the prevailing wind in
order to reach it. It may possibly be true that some insects
are apt to spread in the direction of the prevailing wind, as
Mr. Webster asserts. But, judging from the few examples

* Webster, F. M., ‘ Diffusion of Insects,” p. 797.

- arT x ee ae Or - : , ~ _——
> aa 7 : Pa ee ae eae , SS . —— :

yg vr P = Se - £ Te Ses ~ =_ —— r
om, Ys L, -_ pe a a — 77 7 B® |

DISPERSAL OF BUTTERFLIES 117

he quotes, I do not think there is sufficient evidence for the
belief that insects as a whole are influenced in their dispersal
by that agency. His statement that the influence of high
winds on insects is illustrated by the great number of butter-
flies that are sometimes encountered by ships at sea at long
distances from land, is somewhat misleading. As a matter
of fact, remarkably few species of butterflies have been
observed far out at sea, and these always belong to species
that are in the habit of migrating. It is a well-known
phenomenon that certain species of butterflies and moths,
such as the painted lady (Vanessa cardui), the milk-weed
butterfly (Anosia archippus) and the moth Urania leilus,
congregate into flocks or swarms and migrate in a body at
certain times of the year. And it is such swarms that are
occasionally scattered by storms and carried out to sea.
These are, however, altogether exceptional instances, and we
are not justified in drawing conclusions from them and apply-
ing them to insects as a whole, very few of which possess any
migrating instincts. On the contrary, the facts of the
geographical distribution of insects are, as a rule, quite
in conformity of those of mammals. Even the distribu-
tion of the strongly-winged Sphingidae in North America
shows a distinct division into an Atlantic and Pacific sub-
region. |

I have already alluded, on p. 90, to the range of the genus

. Of butterflies Parnassius in North America, pointing out that

it had apparently entered the continent in Alaska and had
then spread along the Rocky Mountain chain. Altogether, the
butterflies and moths of the Rocky Mountains show a close
resemblance to those of the Old World ; among them we meet
with the familiar genera Colias, Argynnis, Erebia and
Oeneis.* The main advance has apparently taken place in a
southward direction from the north along the crest of the
mountains. :

Much remains to be done before we can obtain even a
general idea of the beetle fauna of the Rocky Mountains, but
it is certain that many Old World genera and’ even species
have travelled southward along this chain for a considerable

* Pagenstecher, A., ‘“ Lepidopteren d. Hochgebirges,” p. 145.

118 ORIGIN OF LIFE IN AMERICA

'

distance. On the other hand, typically American genera, like
the oil beetles (Hleodes), have gained access to heights up to
8,000 feet in the southern spurs of the Rocky Mountains.

Of fossil insects, in spite of Mr. S. H. Scudder’s * classic
researches and Dr. Handlirsch’s splendid tréatise, we know
comparatively little. But our knowledge has been particularly
enriched by the discovery, in the midst of the Rocky Mountains
of a deposit of shales containing a wealth of the most beauti-
fully preserved specimens of insects and plants. During one
of the voleanic eruptions, which were so frequent in Tertiary
times throughout the greater part of the Rocky Mountains
region, great masses of leaves and innumerable insects were
entombed among the fine volcanic ash, and were thus readily
preserved. Over six hundred species of insects are now known
from these Florissant shales of Colorado, which, according to
Professor Cockerell 7 are not of Oligocene age, as Mr. Scudder
thought, but of Miocene age. The absence of mammalian
remains, however, increases the difficulty of estimating the
exact age of these deposits. Itis possible, moreover, that some
of the shales may be much older than others.

I cannot leave the Rocky Mountains without expressing a
few words of appreciation as to the wisdom and forethought
of the Americans in preserving large tracts of country in the
wild state. These large land reserves, as Mr. Roosevelt { so
forcibly reminds us, are mainly to keep the forests from
destruction, but likewise to preserve, for future generations,
the wild animals that live in them.

The first and most famous game preserve in the world was
established in 1872 and set apart as a public park or pleasure
ground for the benefit and enjoyment of the people. Congress
provided against the wanton destruction of fish and game, or
their capture or destruction for merchandise or profit. Asa
result of this wise enactment we find to-day thousands of
deer of various kinds in this magnificent world-famed en-
closure known as the “ Yellowstone Park,” the name being
derived from Yellowstone, the largest tributary of the Missouri

* Scudder, 8. H., ‘‘ Tertiary Insects of North America.”
+ Cockerell, T. D. A., ‘“‘ Fauna and Flora of Florissant,” p. 160.
t Roosevelt, Th., ‘‘ Wilderness Reserves,”’ pp. 23—24.

<a e

Ry eed

Se a
. ~ - 2 pe aeery :

7 >
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NATIONAL GAME PRESERVES 119

River. I need not enlarge upon the fascinating spectacles of
the hot springs or the geysers, waterfalls and other natural
wonders which attract sightseers to this district.

Since the opening of the Yellowstone Park, largely owing
to the efforts of the Boone and Crockett Club and its founder
Mr. Theodore Roosevelt, many other game and forest pre-
serves have been established in the United States. The
American Bison Society and the New York Zoological Society
also worked incessantly towards the same end, so that at pre-
sent over seven million acres in the United States are devoted
to the preservation of the native fauna and flora. The two
largest enclosures are the Yellowstone Park in Wyoming, and
the Grand Canon Game Preserve in Arizona. This growth of
sentiment in favour of protecting animals and plants from
destruction has also spread beyond the borders of the States
into Canada, and induced the authorities there to imitate these
beneficent measures. In their enthusiasm to vie with their
neighbours, Canadians have even provided game preserves
which exceed in size the largest of those referred to, for the
new Jasper Park in Alberta has an area of nearly three and a
half million acres, while Rocky Mountain Park in Alberta
has two million seven hundred thousand acres. ‘Two others
have over a million acres.

Hidden game preserves of the past life of North America,
as I mentioned before, lie among the vast accumulations of
Tertiary rocks in the same mountains that shelter the modern
representatives of the American fauna. In the beginning of
the chapter I just alluded to the names of some of the more
important deposits and the geological formations they belong
to. Hnough is now known of the remains of the animals con-
tained in these deposits to enable palaeontologists to compare
their relationship with that of fossil assemblies of animals in
other continents. Professor H. F. Osborn has recently pub-
lished an excellent summary of our knowledge of these western
beds and their mammalian fauna, and I cannot do better than
quote some of his conclusions.

The Hocene Tertiaries of the mountain region, lying in the
Rockies and west of them, were partly formed by. the post-
Cretaceous or post-Laramie uplift, accompanied by great
voleanic activity, lava flows and eruptions of volcanic dust, and

120 _ ORIGIN OF LIFE IN AMERICA

by the formation of a series of lake, river and flood-plain
basins, filled with voleanic and erosion sediments. — During
the first faunal phase of the Eocene Period a land connec-
tion with South America seems to be indicated by the occur-
rence of similar mammals in the upper Cretaceous or basal
Hocene of Patagonia. Additional evidence of South American
connection is afforded by the subsequent occurrence of animals
related to the Edentata-Dasypoda in the American middle
Kocene. A momentous change occurs, according to Professor
Osborn, during the second faunal phase of the Eocene.
Similar faunas appear almost simultaneously in south-western
North America and in western Europe. In Professor
Osborn’s * judgment this remarkable circumstance is due to
the gradual southward extension of the fauna from a hypo-
thetical northerly American-Asiatic land mass.

Not a single specimen of an Hocene mammal has been dis-
covered in northern Asia or the northern parts of North
America. Professor Osborn and many other authorities
assume the Hocene existence of a great American-Asiatic
land mass, because large tracts of land in the north certainly.
are very ancient, and must have been raised above the sea in
‘Hocene times. That is about all the evidence we possess
for the belief that the great similarity of the western European
and western North American fauna during the Eocene Period
was due to some land connection via northern Asia and
northern North America.

I should prefer to throw my hypothetical land bridge
straight across the Atlantic from western Europe ‘to North
America. In another chapter I shall endeavour to show that
we possess important zoogeographical evidence for the belief
in such a transatlantic bridge in Kocene times. Professor
Schlosser + contends that geological researches are alone
capable of yielding information about former land connec-
tions. He does not believe that much weight can be attached
to ancient reconstructions of continents based on zoogeo-
graphical or distributional data. I hold, on the contrary, that
since certain old groups of animals, even genera and species,

* Osborn, H. a Cenozoic Mammal Horizons,” pp. 19—35.
{ Schlosser, M., ‘‘ Uber Tullberg’s System der Nagetiere,” p. 748.

OO ee ee a ee

DEPOSITS OF THE TERTIARY ERA 121

have originated in the far distant past and are now scattered _
here and there in isolated colonies, their present range indi-

cates former conditions’ of land and water. By comparing

the discontinuous distribution of such old groups in the dif-
ferent continents, we come to certain conclusions as to the
conditions of the continents during the time when their range
was continuous. We have already become acquainted with
several genera and species showing discontinuous distribu-
tion. I argued, in the first and fourth chapters, mainly from
distributional evidence, that North America was connected
with north-western Europe and with north-eastern Asia in
Pliocene times. We know of relict genera and species which
represent the life and the geographical conditions of still
more remote stages of the Tertiary Era, namely, the Miocene,
Oligocene and Hocene, and even periods of the secondary or
Mesozoic Era. We thus possess in our recent fauna an invalu-
able adjunct to palaeontological research. That this state-
ment is not a mere assumption will be amply demonstrated in
the next few chapters.

Returning to Professor Osborn’s researches, he directs at-
tention to the striking diminution of Huropean types in the
last stages of the Hocene deposits. This, he argues, might
have been due to the existence of prolonged geographic or
climatic barriers between the two continents. In Oligocene
times the faunal community with western EKurope once more
becomes closer. It is important to note, Professor Osborn re-
marks, that many American lower Oligocene types are repre-
sented by more primitive forms of European upper Hocene and
partly of north African types. This stage is followed by a long
period of independent evolution and partial extinction of the
Same fauna to the close of the lower Miocene age. About the
middle of the Miocene Period another profound change in
the mammals of North America occurs. This is mainly due to
the sudden appearance of a large number of new forms of
African and Eurasiatic origin, such as the elephants, which
are believed to have come from Africa, and the rhinoceroses
and the true ruminant animals, which are supposed to have
had their home in Asia or Europe. These North American

_ middle Miocene deposits contain animals which first appear

in the lower Miocene of Europe. Hence there is distinct evi-

199 ORIGIN OF LIFE IN AMBRICA

dence for the assumption that the general movement of the
fauna has been from the Old World to the New. Finally,
in the Pliocene beds of North America, we perceive clearly
that an invasion of South American animals has taken
place.* :

‘

* Osborn, H. F., ‘‘ Cenozoic Mammal Horizons,”’ pp. 42--82.

CHAPTER VI
ANIMALS OF THE EASTERN STATES

Wen a naturalist from western Europe crosses the Atlantic,
and after landing at one of the great ports on the east coast
of the United States, takes a stroll in the country on a fine
summer’s day, a great many novel features strike his eye.
Let us suppose, for instance, that he is specially interested
in reptiles and amphibians. Although the neighbourhood of
New York and Boston abounds with ideal dry sandy banks
which would be alive with lizards if situated in France or
Germany, these reptiles seem to be completely absent. This
is actually the case. No lizards have been observed in the
neighbourhood of these cities. If he went further inland
to ascertain whether America is really devoid of lizards, our
visitor might succeed, after crossing the Hudson River, in
capturing some. ‘Two kinds of lizard have been recorded
from the western parts of the State of New York, viz., the
blue-tailed lizard (Eumeces quinquelineatus) and the common
_ swift (Sceloporus undulatus).* The first of these is a strik-
_ ingly handsome species with five vividly yellow lines along
the back and a tail of brilliant blue. It is altogether different
from the ordinary Kuropean lizards, for the scales are shiny
like those of the slow-worm. ‘The blue-tailed lizard forms
_ part, in fact, of the large family of skinks (Scincidae) most
_ of which inhabit the tropical portions of the Old World. The
genus Eumeces (Plestiodon) to which the American blue-
tailed lizard belongs, is largely confined to the south-eastern
_ and southern States of North America. A few species are
_ found in the south-west and in Mexico, while the genus is
_ entirely absent from South America and Europe. Hight
_ ‘Species are known from Asia. Now the most remarkable point

* Eckel, E. C., and F. C. Paulmier, ‘“‘ New York Reptiles,” p. 390.

124 ORIGIN OF LIFE IN AMERICA

about this blue-tailed skink is that a species, until recently
considered absolutely identical with it, is found in Japan,
being unknown on the mainland of Asia. Some differences
have now been detected between these two skinks, but they
are no doubt very closely related to one another. Weare con-
fronted, therefore, with the extraordinary problem how to
account for the occurrence of two species, so nearly akin,
in localities so distant from one another. It must be clear to
anyone who is familiar with distributional problems that acci-
dental dispersal within recent times either by man or by
any other agency is out of the question, This is a case of
geographical distribution which must be explained by the
ordinary modes of migration. If it was quite a unique
Instance of such a remarkably discontinuous range, it might
be a matter of some difficulty to discover a plausible explana-
tion to account for it. But it is by no means the only example
of such arange. Quite a number of instances are known. A
still more striking one is that of the so- called ground lizard
(Lygosoma laterale).*

The ground lizard, with its minute limbs, thick tail and
sluggish movements, reminds one more of a salamander than
a lizard. It lives, moreover, under the bark of trees or among
rotten wood, and is thus altogether different in habits from
the ordinary lizard. Now this peculiar ground lizard oceurs
in identically the same form in North America, in China and
Japan.f The most searching comparison by the best experts
has hitherto failed to elicit the slightest difference between
thé Asiatic and this North American ground lizard.

It is interesting to note that the ground lizard and
the blue-tailed lizard, both of which exhibit such a remark-
ably East Asiatic relationship, are members of the family
Scincidae. But, whereas we possess in America over thirty
species of the genus Humeces, to which the blue-tailed
lizard belongs, there are only two American species of
Lygosoma. We now have to ascertain whether these twa
genera Humeces and Lygosoma, are of American origin, or

* Cope, E. D., ‘‘ Crocodilians, lizards and snakes of North America,”
p. 622.
T Stejneger, L., ‘‘ Herpetology of Japan,” p. 219.

ee ee ee ee

LIZARDS OF THE EASTERN STATES 125

whether they have come to America from some other part
of the world. Lygosoma laterale is known from eastern
Mexico in the south-west, and from all the southern and
eastern States as far north as New Jersey. Altogether fifty
species of the division of Lygosoma, to which the American
species belong, have been described.* Five of them live in
New Zealand, twenty in Australia and the adjacent islands,
seven in the Pacific Islands, four in the Philippines and
Borneo, seven in India, two in the Nicobar Islands, one in
Mauritius, two in West Africa, one in Central America, while
a single species, as far as we have learnt, is found in China,
Japan and North America. The wide range of the species in
North America shows that it has not been introduced. It is
no doubt indigenous. Yet, to judge from the range of the
genus Lygosoma, America is certainly not its home. We may
also safely conclude, from its most discontinuous range, that
it is of very great antiquity, although quite unknown as a
fossil. New Zealand, according to Dr. Wallace,} received its
flora and fauna during the latter part of the Secondary Era,
and has not since been connected with any mainland. Since
this view has been widely accepted, it would tend to show
that the genus Lygosoma was already in existence in

4 Mesozoic times, and that it possibly gained its present

distribution towards the end of the Secondary or early in
the Tertiary Era.

The second genus Humeces may help us in our enquiry
as to the mode of entry into North America. There are about
twenty species of Humeces in North America, ranging from
Mexico in the south to Minnesota in the north, and New
Jersey inthe east, Considerably over one-half of these inhabit

€ the south-western States and Mexico. Certainly the centre

of distribution in America lies in the south-west. The various
Species seem to have radiated from this centre in all directions

' except the south. The genus must have existed in this south-
_ western centre for a very long time past, because one species

peculiar to an island in the Bay of Campéche, another to the

Island of Bermuda, and still another to southern Florida, are

_* Boulenger, G. A., “‘ Catalogue of Lizards,’ Vol. III., pp. 253—289.

+ Wallace, A. R., ‘ Island Life,” p. 506.

126 ORIGIN OF LIFE IN AMERICA _.

known to science. Eumeces must have lived in North
America possibly since early Tertiary times. The genus has
also been observed in India. One of the species ranges from
Baluchistan, right through Persia, Syria and Egypt to Tunis,
having there probably given rise to the allied form confined
to Algeria and Morocco. :

If Eumeces had already existed in south-western North
America in early Eocene times, we should expect it to have
travelled to South America during the supposed Eocene land
connection with that continent. That it has not done so may
be due to the fact that its original home is in south-eastern
Asia. This assumption is strengthened by the circumstances
that its nearest relations are the genera Tribolonotus of New
Guinea, and Brachymeles of the Philippine Islands.

Since Lygosoma, like Humeces, also occurs in the south-
western States, it may likewise have made its entry into North
America in that region, though its original home seems to have
been somewhere in the western Pacific. Being probably an
older genus than Eumeces, both may, nevertheless, have taken
the same route in reaching North America. Where that route
lay and what were the geographical features of North America
at the time will be discussed later on when more material has
been gathered from other sources.

‘I alluded above to another lizard which has penetrated as
far north as New Jersey, namely, the swift (Sceloporus undu-
latus), so called from the great activity and speed of its move-
ments.* Its scales are strikingly different from those of the
skinks. They are large and coarsely keeled, terminating in
sharp, bristly points. The swifts belong to the typically
American family Iguanidae. All the Iguanidae, and there are
many of them, are confined to North and South America, with
the exception of one genus which inhabits the Fiji Islands
and two others living in Madagascar. It is quite possible,
however, as Dr. Gadowy suggests, that the Madagascar genera
represent cases of convergent evolution from some common
ancestor.

Although a species of Iguana has been described from the

* Ditmars, R. L., ‘*The Reptile Book,” p. 123.
+ Gadow, H., ‘‘ Amphibia and Reptiles,” p. 501.

oo

a —————— a

388.

SNAKES OF THE EASTERN STATES 127

Eocene deposits of France and England, we have no reason
to doubt that the family has originated in America. The
Cretaceous genera Iguanavus and Chamops from Wyoming,
have always been considered as belonging to the Iguanidae.
Since the family scarcely enters eastern America even at the
present day, the western States must always have been its
headquarters. How the dispersal from the American con-
tinent to the Fiji Islands was effected is another siete
which I defer to a later discussion.

As for the genus Sceloporus, to which the swift (5. undu-
latus) belongs, almost all the species inhabit Mexico, that
country forming the centre of distribution. From there the
genus ranges as far south as Nicaragua. One species occurs
in the western States, while the single northern species,
Sceloporus undulatus, ranges from Guatemala to the eastern
States. Both the nearest relations of this genus, Phrynosoma
and Uta, have their headquarters in the south-western States
and Mexico. We possess, consequently, satisfactory evidence,
both from its recent as well as its fossil distribution, that
thé family Iguanidae is of North American origin, and that
the latter can be traced to the end of the Mesozoic Era.

In spite of the occurrence of these three species of lizards
in some of the north-eastern States, these reptiles certainly
are scarce in the east. It is not so with the snakes. No less
than twenty-three different kinds have been observed in the
vicinity of New York,* whereas in the whole of France there
are only about half that number. The eastern States of
America are, in fact, remarkably rich in snakes. Snakes have
even penetrated to the eastern islands, for several species, in-
cluding the dreaded rattlesnake, occur in Long Island.

The commonest of these eastern and probably of all the
American snakes, is the garter-snake (Thamnophis or Eutenia
sirtalis). It is abundant from southern Canada to Florida,
and I have met with it even on the edge of the White Moun-
tains plateau at a height of 5,000 feet. Very closely allied
to, and scarcely distinct from the genus Tropidonotus, the
garter-snakes (Thamnophis) form a most troublesome group

* Kekel, E. C., and F. OC. Paulmier, ‘‘New York Reptiles,” p. 356—

128 ORIGIN OF LIFE IN AMERICA

from a systematic point of view. Several of the species are
exceedingly variable, and all are difficult to discriminate from
one another. :

The genetic relationships of the various species and the
causes which have given rise to the differentiation of the
garter-snakes are most attractive subjects for study. Dr.
A. H. Brown * has discussed the connection between moisture
and variability, especially in the direction of colour intensity
in this group of snakes. More recently an ingenious and
novel method of carefully estimating the value of the cha-
racters commonly held to be specific in snakes has been
adopted by Dr. Ruthven. He shows that the reductions in the
number of rows of dorsal scales as the girth of the body
decreases in the individual snake, are brought about by the
dropping of certain definite rows. This leads him to the con-
clusion that specific variation in the scale rows follows the
same sequence and is also correlated with the circumference
of the body. Similarly, presence, absence or fusion of the
labial scuta are dependent on the length of the head. Dr.
Ruthven’s + assumption is that the garter-snakes started in
America with the maximum number of dorsal rows of scales
known in the genus, and that the forms resulting from geo-
graphical extension are mostly due to dwarfing in consequence
of unfavourable environment. He then traces four lines of
descent, which all emanate from northern Mexico as the centre
of origin of the genus. ‘The area inhabited by the nineteen
species of garter-snakes includes all North America and south-
ward as far as the southern boundary of Guatemala. The
genus is evidently a geologically recent immigrant to Central
America.

It is of the greatest interest to the student of zoogeography
that Thamnophis differs from its nearest American relative,
Tropidonotus, by the absence of scale pits, and by the pre-
sence of an undivided anal plate, for it seems almost certain
that Thamnophis has originated in North America from some
ancestral form of Tropidonotus (Natrix), the latter being
clearly a much older genus. Tropidonotus has a vast range

* Brown, A. E. Variations of Eutaenia.”’
+ Ruthven A. G. “ Variations of the Garter Snakes.’’

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ORIGIN OF THE GARTER SNAKES 129

from north Australia through the Malay Archipelago and
northward to Japan. Westward it extends to India, Africa
and Europe. In America the genus occurs principally
in the eastern States, but there is also a species in Cuba
and several in Central America. None have penetrated
to South America. From Dr. Boulenger’s * catalogue and
Dr. Stejneger’s description of Japanese forms,f it seems
evident that the east Asiatic forms are not very closely
related to the American ones. On the other hand, Tro-
pidonotus validus, from Lower California, Arizona and
Mexico, is nearly akin to the west Huropean Tropidonotus
viperinus, whose high antiquity is indicated by its oecur-
rence in Sardinia and Algeria. I may have another oppor-
tunity later on of dealing with this interesting genus, but
it must be conceded that although we possess no fossil
evidence, the origin of Tropidonotus must date back at least
to the commencement of the Tertiary Kra. In another chapter
I shall show how extraordinarily intimate is the relationship
of the south-west American and the West European faunas.
Evidence will then be given in support of the theory that
southern Europe and the south-western parts of North
America have been connected with one another by land, and
that we probably owe the resemblance in the animals and
plants of these two regions to that fact. The species of
Tropidonotus, in America at any rate, are semi-aquatic. They
are so much attached to water that they are popularly known
as “ water-snakes,” whereas the garter-snakes are much less
bound to the neighbourhood of water. The latter are not
uncommonly found on higher ground and in drier situations,
a change in the climatic conditions of the south-west may thus
originally have given rise to the Thamnophis branch from the
original Tropidonotus stock. The headquarters of Tropi-
donotus now lie in the eastern States, where the conditions
for its existence are more favourable than in the south-west.
All the same, it seems probable that the original centre of dis-
persal was in the south-west, for when Tropidonotus arrived

* Boulenger, G. A., “ Catalogue of the Snakes in the British Museum,’,
Vol, 1.

T Stejneger, L., “ Herpetology of Japan,” pp. 264—294.
L.A.

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130 ORIGIN OF LIFE IN AMERICA

in North America the climate of that region must have been
very different from what it is at present.
I may just mention two other examples of innocuous snakes
which frequent the north-eastern States, viz., the smooth
green snake (Liopeltis vernalis), and the rough green snake
(Cyclophis aestivus). The former is abundant in New York
State and northward as far as south-eastern Canada. South-
ward it ranges to the Gulf of Mexico and westward to New
Mexico, becoming rarer as we approach the drier and warmer
districts. The other does not extend nearly so far north. On
the other hand, the rough green snake is found westward as
far as northern Mexico and California. Both of them share
the peculiarity of being the only members known in America
of the genera to which they belong. That is not the only fea-
ture of interest about their distribution. I have just urged
that the ancestors of the American species of Tropidonotus
must have come from Hurope. We cannot claim the same
origin for the American species of Liopeltis and Cyclophis,
for neither of these genera inhabits Europe. Both,of them are
absent also from Africa. Their headquarters are in southern
and eastern Asia, but they do not extend as far north as Japan.
Formerly these snakes were classed among that insoluble
zoogeographical enigma, namely, the group of animals and
plants peculiar to eastern Asia and eastern America. Now
we have advanced in so far as we have been able to trace
some of the eastern forms to an originally western American
range. It has been made easier, therefore, for those natura-
lists who are in the habit of explaining anomalies of dis-
tribution by the convenient flotsam-jetsam theory, to bring
their views to bear upon problems such as those suggested
by the two green snakes. That these snakes could have been
. floated across the Pacific Ocean on a raft by any possible
chance, is to me inconceivable. That they should have utilised
the Bering Strait land connection, and subsequently have
become extinct all along north-eastern Asia and north-western
North America does not appeal to me either as likely. We
must only leave the consideration of the problem for the pre-
sent, us was done in the case of the lizard genera Humeces
and Lygosoma, which also apparently had an east Asiatic
origin. !

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RANGE OF RATTLESNAKES: 131

From the popular point of view, as Dr. Ditmars * remarks,
the venomous rattlesnakes are the most interesting of the
American serpents. The Old World naturalist involuntarily
associates America with rattlesnakes; and the ominous warn-
ing sound produced by the unique appendage at their tail
alone exercises a strange fascination on everyone who has
become acquainted with them. Not only is the common rattle-
snake (Crotalus horridus) abundant in some of the hilly por-
tions of New York and Massachusetts, it actually appears to
be increasing in numbers in these populous States, owing to
the decrease of its natural enemies. From a zoogeographical
point of view rattlesnakes are of considerable importance,
because, being strictly limited to the ground, they are less
liable to accidental dispersal than the members of many
other genera which are expert swimmers or fond of climbing
trees. The rattlesnakes are generally divided into two genera,
viz., the pigmy rattlesnakes (Sistrurus) and the rattlesnakes
proper (Crotalus). Both genera range almost all over the
United States, a couple of species even cross the borders

- of Canada. Southward, Sistrurus is also met with in Mexico.
_ ‘The true rattlesnakes (Crotalus), on the other hand, have a
a much wider distribution in America, one species (C. terrificus)
having been found in Mexico as well as in Yucatan, Bolivia,
_ Venezuela, northern Argentina, and southern Brazil.

Remains of rattlesnakes have been noticed in a couple of the

North American caves, otherwise they are unknown in earlier
_ deposits. Their range is confined to America, and we have
_ no reason to suppose that they have originated in any other
_ continent. Their home is, no doubt, as Dr. Brown + suggests,
in the south-western States in what he calls the Chihuahuan

district. We have no means of estimating the age of the two
genera of rattlesnakes. Yet Crotalus seems to be the more
ancient, and, like its near relation Lachesis of southern Asia,

Central and South America, has probably a remote ancestry.
_ It may possibly have inhabited North America since early
Tertiary times.

I have drawn particular attention to the fact that the

_* Ditmars, R. L., “The Reptile Book,” p. 426.
+ Brown, A. E., “Texas Reptiles and their Faunal Relations,” p. 558.

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132 ORIGIN OF LIFE IN AMERICA

great scarcity of lizards and the abundance of snakes are
_ characteristic features of the north-eastern States of North
America. But I have not yet alluded to the most remarkable
feature of the reptilian fauna of that region, as it is not a
character readily noticeable to the untrained naturalist. It
is the great wealth of land and fresh-water tortoises. In
England it is customary to distinguish the marine, paddle-
limbed kinds of Chelonians as “ turtles,” all others as “ land
and water tortoises.” In America the term “turtle” is
usually employed quite indiscriminately to true tortoises and
turtles. In adopting the common American names applied
to these tortoises, | am only endeavouring to make my
remarks quite clear to American readers.

I have had occasion already to refer to one species of
fresh-water tortoise (p. 51), sometimes called “ semi-box ”’
turtle (Emys blandingi), and to discuss the peculiar range
of the genus, which is confined to parts of Canada and the
northern States in America, and to central and southern
Europe in the Old World. We possess no fossil remains of
any members of the genus except from recent geological
deposits. Although we must assume that a migration has
taken place either from North America to Europe, or vice
- versa, in more remote times, palaeontology gives us no clue
as to the origin of Emys. We can only surmise that the
genus and species of Emys are ancient from the fact that
the genus Clemmys occurs in the HKocene of North America,
while Chrysemys has been discovered in the Kocene of
Europe. Both of these are still living genera of turtles and
closely allied to Emys. They are classed among what are
called “‘ terrapins ” in North America.

The terrapins are characterised by their broad, flattened
shell. The hind feet are extensively webbed, and they are
good swimmers. Perhaps the best known of the terrapins
is the ‘‘ diamond-back ” (Malacoclemmys centrata)* which
frequents the salt marshes of the Atlantic coast. It is in
great favour in the States as an article of diet. The less ~
familiar spotted turtle (Clemmys guttata) is of greater zo0o- —

* Ditmars, R. L., “The Reptile Book.” Siebenrock, F., Synopsis
der Schildkréten.”’

AMERICAN TURTLES _ 188

geographical interest. Four species occur in North America, |
three of them being limited in distribution to the eastern
States. Only one, viz.: Clemmys marmorata, is quite con-
fined to the rivers and ponds west of the Cascade and Sierra
Nevada Mountains in Oregon and California. In Central
and South America the genus is unknown, but in eastern
Asia we find four species. One of them inhabits Japan,

another the island of Hainan, and a couple of them China.

Far away in western Asia we meet with another species in
Persia and Mesopotamia, spreading across Asia Minor to
Greece and Turkey, while finally Clemmys leprosa lives in
Spain, Portugal and north and western Africa as far as Sene-
gambia. The genus is thus quite confined to the northern.
hemisphere. We might suppose that the ancestor of the
American Clemmys insculpta had spread northward from
eastern Asia in Pliocene times and, after crossing the Bering
Strait land bridge, had invaded Alaska and Canada, ulti-
mately reaching the eastern States of America in that
manner, and subsequently becoming extinct in the vast tract
of country which now separates the Chinese from the eastern.
American species. The south-western Clemmys marmorata
would thus have been the latest development of the genus
in America. Such a supposition seems unlikely, owing
to the unsuitability of the western States for such
turtles. The few that now inhabit the west are rather to be
regarded as ancient survivals of a long-distant age when
the climatic conditions were much more favourable for them
than at present. The earliest member of the genus indeed
(C. morrisiae), is found in a western Eocene deposit (Bridger
beds), and Dr. Hay * expresses the opinion that North
America is probably the original home of Clemmys. If so,
the genus could not possibly have spread to Asia, and thence
to western Europe in Pliocene times. The existing centres
of distribution must have become established during much

More remote geological periods. Anyhow, although the

majority of the American species of Clemmys are now con:
fined to the east, we have ample palaeontological evidence
of its having formerly lived in the west.

* Hay, O. P., “ Fossil Turtles of North America,” p. 290,

134 ORIGIN OF LIFE IN AMERICA

Besides these so-called fresh-water turtles, we have in
America even terrestrial ones. The box-turtles (Terrapene
= Cistudo), for instance, are strictly confined to the land, where
they live largely on vegetable matter and berries. The six
species are distributed from Mexico in the south-west to the
New England States in the north-east. In the more northern
habitats they burrow to some depth in soft ground and pass
the winter there. All the box turtles inhabit North America,
the genus Terrapene to which they belong being, in Dr. Hay’s
opinion, of North American origin. The oldest fossil species
(T. putnami) comes from a deposit in Florida stated to be
of Pliocene age. Dr. Hay * is inclined to the belief that the
genus arose in North America, having probably been derived
from Emys. If this should be the case, the origin of Emys
itself must have taken place at a much earlier date than the
Pliocene. Indeed it is possible that Emys is one of the most
ancient of Chelonian genera, for Dr. Boulenger + argued that
it is in many respects the least specialized of the Emydidae
and that it should be placed at the base of the family. It is
of interest to note that although box turtles lived in North
America at least since Pliocene times, they have not been
able to spread beyond the confines of the continent. This
gives us some idea of the slow rate of dispersal of these
creatures.

Of the family of snapping turtles (Chelydridae) a few
fossil remains are known from the Jurassic and Cretaceous,
though not of existing genera. ‘To judge from their distri-
bution the latter must nevertheless be very ancient. These
large fresh-water Chelonians with their proportionately huge
and sinisters heads, are, according to Dr. Ditmars, bold and
aggressive fighters, their massive, keen-edged Jaws causing
them to be the terror of most of the aquatic and semi-aquatic
creatures. ‘There are three species in North America. One
of these ranges from Mexico, east of the Rocky Mountains,
to Canada, but far to the south of Mexico the same species
(Chelydra serpentina) reappears in Ecuador. Such a very
peculiar discontinuous range is not unknown among fresh-

* Hay, O. P., “ Fossil Turtles of North America,” p. 360.
+ Boulenger G. A., “ Catalogue of Chelonia,” p. 49.

GIANT SALAMANDERS | 135

water animals, as we shall learn later on. A second species
(Chelydra rossignonii) is confined to Mexico and Guatemala.
The so-called alligator snapping-turtle (Macroclemmys tem-
minckii), which belongs to another genus, frequents the
rivers emptying into the Gulf of Mexico, being common in the
Mississippi as far north as Missouri. Now the most striking
zoogeographical feature of the family Chelydridae is, that
right across the Pacific Ocean we meet with another snapping

turtle (Devisia mythodes) in the Fly River of New Guinea,

the same river that contains the unique members of the family"
Carettochelyidae. In many other respects New Guinea has
acquired the reputation of being the home of remarkable and
peculiar types of animals, and no doubt the island once
formed part of an ancient land, most of which has long since
been submerged.

Quite as instructive and important from a distributional
point of view as the reptiles are the amphibians. We can
roughly divide the latter into tailed amphibians, such as the
newt and salamander, and tailless ones, of which the frog
and toad are examples. All these are amply represented in
the north-eastern States of North America, and we notice
among them that same curious relationship between eastern
America and eastern Asia which has given rise to so much
comment among naturalists.

Two kinds of giant salamanders are known to exist in the
world. One of these, the so-called “ hellbender ” (Crypto-
branchus allegheniensis), lives in the eastern States of North
America, the other, (Cryptobranchus or Megalobatrachus
japonicus), in the mountain streams of Japan. ‘The hell-
bender is a voracious lead-coloured slimy creature, living
in the Allegheny and other eastern rivers, where it feeds on
worms and fish. It grows to a length of two. feet, while
its Asiatic relative attains to double that size. Of the geo-
logical history of the giant salamanders we know nothing
as far as America and Asia are concerned, but in the Miocene
of Switzerland a large amphibian was discovered, which
appears to be closely allied, though now referred to the
distinct genus Proteocordylus. To suppose that these relicts
of bygone ages are no older than Miocene would scarcely be
justified. In the absence of palaeontological evidence, we must

136 ORIGIN OF LIFE IN AMERICA

depend upon the testimony based on the remarkably discon-
tinuous ranges of the two recent species. Any theory as to
the home of the giant salamanders should be founded on that
of other animals possessing a similar range.

The hellbender is not the only large amphibian frequent-
ing the rivers of the eastern States. A somewhat eel-like
creature, with feeble diminutive limbs and three pairs of
bushy external gills, inhabits many of the larger streams
and lakes in the north-eastern States.* It grows to about the
same length as the giant salamander, but belongs to quite a
different family. It is commonly known as the “ Mud puppy ”
(Necturus maculatus), and does not occur west of the Rocky
Mountains. Now in this case the nearest relation of the east
American form does not live in Eastern Asia, but, like that
of the mud minnow (see p. 51), in EKastern Europe. This
European member of the family Proteidae has manifestly
undergone a certain amount of degeneration. It possesses
only three fingers and two toes, is completely blind, and is
restricted to the subterranean waters of Dalmatia and the
neighbouring provinces of southern Austria. The “‘Olm”’
(Proteus anguineus), as it is called, is scarcely a foot long,
and quite white except for the gill bunches which are
brilliantly red in colour. It was believed that the Texas
subterranean newt (Typhlomolge rathbuni) was related to
the mud puppy. Miss Emerson,} however, has shown that
itis asalamandrid. No fossil remains of any of these amphi-
bians are known, and any theories as to the origin of the
discontinuous distribution of the members of this ancient
family, must be based on zoogeographical data. .

The family of true salamanders and newts aalasnanividest
likewise comprises certain members which seem to be of
very ancient origin; such as the blunt-nosed salamanders
(Amblystoma). Being only semi-aquatic animals, they
possess greater facilities for dispersal than the purely fresh-
water forms. Most of them are large species, the tiger sala-
mander (Amblystoma tigrinum) growing to nearly a foot in
length, and they only repair to the water in the spring to

* Cope, E. D., “ Batrachia of North America,” p. 26.
+ Emerson, E. T., “ Anatomy of Typhlomolge,” p. 72,

NEWTS AND SALAMANDERS 137

deposit. their eggs. The tiger salamander is variable in
colour. Generally of a dark brown, it is marked with
irregular yellow blotches, and is commonly met with under
stones and in decayed hollow trees. At the time when the
Spanish conquerors landed in Mexico, the natives were in
the habit of eating roasted or boiled fresh-water creatures,
which they called “ axolotls.”” It is now known that these
axolotls are nothing but the larval forms of the tiger sala-
mander, which is found from Mexico to the city of New York.
Under certain conditions, the larva, instead of losing its gills
and turning into the terrestrial salamander, retains them,
and continues its existence in the medium in which it was
born, growing into a creature somewhat resembling the hell-
bender, and breeding without leaving the water.

The genus Amblystoma is almost confined to Mexico, the
United States and Canada. Only one species (A. persimile),
which most resembles Amblystoma jeffersonianum of the eastern
States and Canada, inhabits the far distant mountains of Siam
and Upper Burmah. This represents, therefore, another
example of that curious relationship between eastern North
America and Asia. In this case, however, it is with southern
instead of eastern Asia, while the genus in North America occurs
in the south-west as well as in the eastern States.

Several smaller kinds of newts have been observed in
the eastern States. Among them there are several belong-
ing to the genus Spelerpes, which are worthy of special com-
ment. They all display remarkably brilliant colours, and
these make them more attractive than salamanders usually
are. Quite apart from this feature, their method of feeding
is interesting to watch. Like chameleons, they possess an
enormously long tongue, ending in a soft sticky knob, which
is shot out of the mouth with extreme rapidity at any insect
coming within range and likely to be a dainty morsel. About
twenty species of Spelerpes are known to science, the head-
quarters of the genus being in Mexico. Dr. Gadow* dis-
covered several of them at considerable heights. Spelerpes
orizabensis and §. leprosus ascend to 12,000 feet, and 8.
operas to 10,000 feet, above sea-level.

* Gadow, H., “ Mexican Amphibians and Reptiles,” p. 203,

138 ORIGIN OF LIFE IN AMERICA

Their earliest centre of distribution lay in what has been
ealled Sonoraland, or south-western North America, and
from here the species have spread in Miocene times, according
to Dr. Gadow, to the eastern States, to the island of Haiti
and even to Peru. The latter occurrence is of particular
importance, as we shall see later on, when we come to the
consideration of the points of resemblance between the
Mexican and the South American faunas. Still moreremark- _
able is the fact that a single species of Spelerpes (S. fuscus) is
known from some of the remaining fragments of the ancient
Tyrrhenian continent in southern Europe (see Fig. 8). Even
Dr. Gadow,* who shows little inclination for reconstructing
ancient land bridges, does not suggest that this salamander
could have crossed the Atlantic Ocean without their
assistance. He thinks a land connection joining north-
eastern North America with north-western Hurope, by way
of Greenland, might have enabled the south Huropean
Spelerpes to cross from the New World to the Old.
I coneur with Dr. Gadow in the belief of the former
existence of a land bridge in the extreme North Atlantic,
but I am of the opinion that it had not yet made its appear-
ance at the time when Spelerpes undertook its journey to
Europe.

This short’ review of some of the characteristic north-
eastern reptiles and amphibians has clearly revealed a
relationship of some of the older forms with those of southern
and eastern Asia and also of southern Europe. In several
instances it was demonstrated that the eastern States were
not the original home of the genera, but that the North
American centre of distribution lay in the south-west. Hence
it seems possible that the south-west was in remote times, say
about the commencement of the Tertiary Era, the great centre
from which reptiles and amphibians wandered eastward.
Owing to subsequent changes in the climatic conditions. of
the south-west, some genera, and even families, probably
became extinct there, thus obscuring the original relation-
ship of that part of North America with Asia and Europe.
Without fossil evidence to guide us, it would seem as if these

* Gadow, H., “ Mexican Amphibians and Reptiles,” Ip. 244,

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AFFINITIES OF EASTERN PLANTS 139

speculations were based on somewhat unreliable foundation.
We may therefore call to our aid another branch of the geo-
graphical distribution of living organisms, namely that of
plants, so as to test the validity of these theories.

Professor Asa Gray * was the first to direct attention, in
1859, to the striking similarity of the flora of eastern Asia
to that of the eastern States of North America. In a popular
account of the distribution of the North American flora, Sir
Joseph Hooker again alluded to this feature more recently,
stating that there is actually specific identity in about two
hundred and thirty cases, and very close representation in
upward of three hundred and fifty: What is most curious, he
says, is that there are not a few very singular genera of which
only two species are known, one in east Asia, the other in
east America. In some of these instances the Asiatic species
is a widespread plant in east Asia, whilst the American is an
extremely scarce and local plant. This and other conditions
render it conceivable, according to Sir Joseph Hooker,f that
the Asiatic element in east America is dying out.

Still more recently Professor Engler discussed the same
subject very fully. He believes that the number of species
common to the eastern States and eastern Asia is far less
than Sir Joseph Hooker thought. Some of these occur also
in the north, others in western North America. Yet there
are certain plants which exhibit extraordinarily discontinu-
ous distribution, quite comparable to what we have noticed
among reptiles. Monotropa uniflora and Phryma lepto-
stachya, for instance, occur only in the eastern States, in
Japan and the Himalayan Mountains. Professor Engler
looks upon these as relicts of a flora which was uniformly dis-
tributed in Tertiary times between the Himalayan Mountains
and North America. Of the genera Liquidambar, Ostrya,
Platanus, and Castanea, we know that they lived further north
in Tertiary times than they do now. We have also learned
from the Pliocene and Miocene beds of the Rocky Mountains,
as Professor Engler points out, that the flora west of these
mountains was formerly not so distinct from that of the

* Gray, A., “ Relations of Japanese Flora.”
+ Hooker, J. D., “North American Flora,” p. 573,

140 ORIGIN OF LIFE IN AMERICA

eastern States as it is at present. A more pronounced
climatic differentiation between the two parts of North
America supervened, he thinks, in later Tertiary times, and
while many of the species became extinct in the western
States owing to the gradually increasing dryness of the
climate, new forms better adapted to the altered conditions
arose. Hence certain types of plants are represented in the
western States by many, and in the eastern by few species.

It is evident that Professor Engler* favours the view that
the western States were once much more nearly related in
their flora to eastern and southern Asia than the eastern
States, and that the present similarity between the latter.
regions has arisen as a secondary character. . Professor
Engler, moreover, believes—and in this respect my views
differ from his—that Japan, western and eastern America
were connected with one another in the north during the
Tertiary Era and probably even in Cretaceous times, forming
three great peninsulas of land joined at their northern bases.
At any rate, the distribution of plants in America seems to
offer a certain amount of support to the view suggested, that
the relationship of the east American and east Asiatic faunas
is due to the recent geological changes in south-western North
America having obliterated the more striking features of
resemblance between the latter and eastern Asia.

In connection with the character of the north eastern flora
just referred to, I might offer a few remarks on the subject
of the supposed former eastward extension of the land. This
subject was discussed towards the end of the second chapter.
I then maintained that, although the north-eastern States
had been under water in Pleistocene times, unsubmerged
land existed to the eastward quite close to, and including
portions of the present shore-line.

Probably one of the best recognised and most characteristic
elements of the eastern North American floras, as Mr. Hollick
remarks, is the one generally known as the “ Pine-barren
flora,’ which is such a prominent feature throughout the
eastern and southern parts of New Jersey and southward.

* Engler, A., “ Entwicklungsgeschichte d. Florengebiete,” I., pp. 22—
37.

| ian

PINE-BARREN FLORA 141

Now this flora has a curiously discontinuous range further
north-eastward. It disappears from the mainland almost
entirely, but reappears on Staten Island and Long Island.
Still further east comes a stretch of eighty miles of sea,
beyond which the pine-barren flora once more is in evidence
on Martha’s Vineyard and Nantucket Islands. On a limited
stretch of the opposite mainland, near New Bedford, the same
flora again makes its appearance. Further north, isolated
members of the flora such as Magnolia glauca, from near
Cape Ann, are known from certain coastal tracts.

It might be argued that this discontinuous distribution is
due to marine currents or winds, but both the prevailing
winds and the currents set in from the opposite direction.
It would not explain the fact, moreover, that the pine-barren
flora is almost limited to the islands. Hence it seems more
likely that Long Island was connected by land with Cape
Cod, forming @ continuous strip of land, which was separated
from the mainland by a broad river or a lake, as Mr.* Hollick*
suggests. Mr. Hollick’s theory not only explains the method
of dispersal of the southern pine-barren flora, it gives us a
clue to the problem why the northern Helix hortensis, which
has evidently survived as a relict form, should be almost
confined to the islands off the coasts of Maine and Massa-
chusetts. However, while I believe that much of that land
which lay off the Atlantic coast remained unaffected by the
Glacial deposits, and that the southern flora survived the
Glacial Epoch on these islands, Mr. Hollick considers the

eastward extension of Long Island, and with it the pine-

barren flora, of post-Glacial age.

I have mainly dealt with reptiles and amphibians in this
chapter, because they form a very characteristic feature of
the north-eastern States. Besides no opportunity occurred
of mentioning them in the earlier part of this volume.
The mammals, on the other hand, scarcely need further
comment here. Only comparatively few species are peculiar
to this province. Nevertheless, there is an order which

has not hitherto been alluded to, and which contains

some remarkable forms confined to the eastern States. The

* Hollick, A., * Plant Distribution,” pp. 191—201.

142 ORIGIN OF LIFE IN AMERICA

order is that of the Insectivora or insect-eaters. They are
distinguished externally by their small size and soft dense
fur, while many of them are adapted for an underground life
and possess specially modified front limbs for the purpose
of digging.

_ Five different genera of moles (Talpidae) are known from
North America, and three of these are restricted in distribu-
tion to the eastern States. One of them, containing but a
single species, the star-nosed mole (Condylura cristata), has
its headquarters in the north-eastern States, extending north-
ward as far as Hudson Bay, and southward to North Carolina
(Fig. 9). The name was given to it from the fact that a
ring of riband-like appendages surrounds the end of the
muzzle, in the middle of which are situated the nostrils. Like
its European relative(Talpa europaea), it constructs extensive
galleries underground, throwing up a ridge of loose earth
along the line of the tunnels. No fossil remains of the star-
nosed mole having ever been discovered, palaeontology
furnishes no evidence as to its past history, and we must
assume that it has originated. in north-eastern North America.

What is often known as the common mole (Scalops
aquaticus) in the States, is no near relation of the European
species of that description. It is more appropriately called
naked-tailed mole. The Latin name aquaticus was given to
it because its webbed hind-feet led to the inference that it
must be a water animal, whereas it actually lives underground
in dry sandy soil. Two species of Scalops are known, one of
them oecurs from Massachusetts to Florida, the other further
west, in the Indian Territory.

Still another eastern species is the so-called hairy-tailed
mole (Parascalops breweri), whose habits are very similar
to those of the other moles, though it is readily distinguished
from them by its thickly-haired black tail. Its range extends

along the Atlantic coast, from New Brunswick in the north

to North Carolina in the south, and inland to the shores of
the Great Lakes. It is even said to occur on Martha’s Vine-
yard Island off the coast of Massachusetts, which locality is
of interest in connection with the view expressed above as
to this island having formed part of an ancient land surface
now partially submerged.

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STAR-NOSED MOLE 148

As for the geological history of these forms, a number of
insectivores with talpoid dentition have been met with in the
middle Eocene (Bridger) of North America, and referred to
the mole family (Talpidae), but, according to Dr. Matthew,
most of them are incompletely known and of doubtful
affinities.* The first undoubted member of the family (Pro-
scalops) makes its appearance in the Oligocene beds of
Colorado, being apparently related to the modern Scalops.
Owing to their subterranean habits, the moles are rarely
found fossil, except in fissures such as those of La Grive
St. Alban in southern France. Palaeontology does not aid
us materially in solving the problem as to the place of origin
of the Talpidae, or the geological period during which the
moles have wandered from one continent to the other. We
are also entirely in the dark as to the route they have taken
on entering the New World from the Old or vice versa. They
may possibly have spread eastward from the western States,
but a careful comparative study of the living American moles
seems more likely to elucidate this problem than palaeonto-
logical research.

* Matthew, W. D., “ Carnivora and Insectivora of the Bridger,”’ p. 536.

CHAPTER VII bis

THE CONTINENTAL BASIN

‘

Bounpbep in the east by what might collectively be termed
the Atlantic Mountains and in the west by the Pacific Moun-
tain system lies the immense continental basin. It is open
to the sea both in the north and south, extending in one
continuous series of plains and plateaux from the Gulf of
Mexico to the Arctic Ocean. The northern portion of this
great interior basin has already been briefly described in the
second and third chapters. The rivers of this part of the
continent drain eastward to the Atlantic Ocean and northward
to Hudson Bay and the Arctic Ocean. The drainage of the
southern portion is supplied almost entirely by the Missis-
sippi, and is thus discharged into the Gulf of Mexico. It is
this southern section of North America and its fauna with
which I propose to deal very briefly in this chapter.

The low-lying and gently seaward-sloping belt of land
bordering the Gulf of Mexico is known as the “ gulf plains.”’
It.is here in this rich soil that sugar-cane, cotton and rice are
cultivated. ‘The west-central part of the continental basin
is occupied by the “ prairie plains.” By the term “ prairie”
we recognise a level region, either a plain or a plateau, with-
out forests, but clothed in a carpet of luxuriant grasses and
flowering annuals. On their eastern and northern border
these prairie plains merge into the adjacent forested plains,
while in the west they gradually pass into the more elevated
and drier high plains, where bunch grass, with bare intervals
between the scattered tufts, takes the place of the continuous
sod of the true prairies.

There is a widespread popular beliag in Kurope that the
whole of the vast American continental basin is one extensive
prairie or pasture land. This is quite a mistake. As we
approach the Mississippi River from the west we gradually

THE PRAIRIE REGION 145

pass from the treeless prairie to the forest region, which is
continued eastward as far as the Atlantic Ocean. In the
prairie region a struggle has been in progress for thousands
of years between the conditions favouring tree growth and
those adverse to them. The increase in the mean annual pre-
cipitation from west to east is the determinant factor in forest
production. The main cause, therefore, of the absence of trees
in the prairies lies, according to Professor Russell,* in the
climatic conditions, and principally in the lack of sufficient
rain during the long, hot summers.

A thorough survey of the fauna of the prairie region has
still to be made. Dr. Merriam + devotes only a short para-
graph to it. Most other writers have confined themselves ta
a description of one or two typical prairie forms. The sole
attempt to give us a more lucid impression of the general
features of the vertebrate life of the region was made by
Dr. Ruthven.t He noticed that the peculiar conditions of the
prairie region had an effect on the fauna in modifying the
species as they entered this region from the adjoining ones.
Yet he thinks that there is a great difference in the extent
to which the species of eastern North America push westward,
or the plains-forms eastward, into the prairie region, before
becoming modified or checked. Dr. Ruthven’s studies lead
him to the conclusion that the prairie region is an extensive
area of transition between the plains and eastern forest
regions, but he expresses the opinion that the conditions of
environment are either not intensive or not extensive enough
to mould the animals into a peculiar fauna.

What was once the most characteristic animal of the prairie
region is now practically extinct in the United States in its
feral condition. I need no longer dwell on the history of the
extinction of the bison, the animal I am alluding to, for it
has been sufficiently described in the third chapter (pp.
65—67). When discussing the question of the bison’s origin,
I suggested that its ancestors might have invaded North

* Russell, I. C., “North America,” pp. 89—96.

+ Merriam, ©. H., “ Life in North America,” p. 20.

{ Ruthven, A. G., “Faunal Affinities of Prairie Region,” pp. 390—
393.

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|

Me ORIGIN OF LIFE IN AMERICA

America from Asia in pre-Glacial times. Long before the
advent of the European conquerors in the New World, herds
of another large ungulate, the horse, roamed about these same
prairies and no doubt shared the abundant fodder with the
bison. When the Spaniards landed in America in 1521 it was
already extinct, and the natives had not any knowledge even of
the former existence of the horse in their continent. Yet even
in Pleistocene times several different kinds of wild horses
still lived in North America and were probably contem-
poraneous with early man. One of these (Equus giganteus)
| seems to have exceeded in size any known race of horse either
living or extinct.* What caused the sudden extinction of the
wild horse all over America we do not know. Professor
Osborn} suggests that a disease of the nature of the African
“ rinderpest ’’ might have done it. The “ tse-tse fly ’’ renders
thousands of square miles of Africa uninhabitable for horses,
and the invasion of a similar pest into America might pos-
sibly have swept away the whole of the equine stock in a short
time. But the interest aroused among zoologists by the dis-
covery of fossil horses in America was not only connected with
their unexplained disappearance in modern times, it yielded
what was thought to be absolutely demonstrative evidence of
the theory of evolution. Fossil forms no doubt had already
been discovered in Europe which seemed to indicate that
the remote ancestors of the existing horse had five digits on
every foot while intermediate stages with three fully deve-
loped toes were known. In America, horses, or at any rate
animals possessing all the essential characters of a horse,
have been brought to light from very early Tertiary deposits,
possessing four toes and a rudimentary fifth on the hind foot
and short-crowned teeth. These are succeeded in Oligocene
and Miocene strata by others with three toes and short-
crowned teeth. In still more recent deposits, horses occur
with three toes and long-crowned teeth which are finally
followed by horses of the modern type with one toe and long-
crowned teeth.

* Gidley, J. W., “ Revision of North American Species of Equus,”

p. 137,
+ Osborn, H. F., “ Causes of Extinction of Mammalia,”’ p. 835.

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GEOLOGICAL HISTORY OF HORSE 147

In a revision of the American Kocene horses, Mr. Granger*
distinguishes twenty-six species, all the three genera to which
they belong being distinct from the early horses found in
Europe. The American Eohippus appears to be closely re-
lated to the Old World Hyracotherium, while Epihippus ap-
proaches Lophiotherium. We thus have a somewhat parallel
series in the two continents.

In the Oligocene deposits the horses are still small, some
of them less than eighteen inches high at the withers.
Twenty-eight species, belonging to the two genera Mesohippus
and Miohippus, have been described by Professor Osborn.t
Sixty more species are mentioned by Mr. Gidley$ as having
been procured in the Miocene and Pliocene beds, and over half
a dozen more from Pleistocene strata. Thus we know from
America already about one hundred and twenty different kinds
of fossil horses. They gradually increase in size as we pro-
ceed from the older to the newer deposits. The species with
many toes are replaced by others with fewer toes, until we
come to the highest form of specialization in the modern
horse. All that remains of the outer toes is a splint-bone left
on each; side of the single toe, while the teeth which originally
possessed short crowns have now long ones. There is ap-
parently a gradual evolution from smaller and simpler forms
to larger and more complex ones, as we glance from the older
horse remains to the recent ones. And yet nota single gradual
transition from one genus to the other seems to be known.
No wonder that one of our foremost palaeontologists exclaims :
“The supposed pedigree of the horse is a deceitful delusion,
which simply gives us the general process by which the tri-
dactyle foot of an ungulate can be transformed in various
groups into a monodactyle foot in view of an adaptation for
speed, but this in no way enlightens us on the palaeontological
origin of the horse.” § ,

Considering the extraordinary abundance of horse remains
in North America, and even in the south of South America,

* Granger, W., “ American Eocene Horses,” p. 233.

Tt Osborn, H. F., “ New Oligocene Horses.”

t Gidley, J. W., “Miocene and Pliocene Horses of North America.”

§ Depéret, C. H., “ L’évolution des Mammiferes Tertiaires,’ OXL.,
p. 1517.

L 2

148 ORIGIN OF LIFE IN AMERICA

it would seem as if the family Equidae had originated in
America’ and had sent certain offshoots to the Old World
during such times when America was connected by land
with either Asia or Europe. Professor Depéret * certainly
_takes the view that both Anchitherium and Hipparion
reached Kurope by means of a land connection with America,
and that the two continents were several times joined to one
another by land during the Tertiary Era. ‘This opinion is
amply supported by the most weighty zoogeographical evi-
dence, as will be shown in one of the succeeding chapters
(pp. 226—231). There is, indeed, a very general agreement
among palaeontologists on this point. The only difference of
opinion concerns the exact location of the site of these ancient
land bridges.

One of the most characteristic animals of the great plains
is the so-called ‘ prairie dog ” (Cynomys ludovicianus). The
name has been applied to it on account of the peculiar barking
sound it emits when alarmed. Otherwise it has nothing to do
with the dog family, being more nearly related to the ground
squirrels and marmots. It loves the sunshine and a dry
atmosphere, and becomes less and less numerous as we ap-
proach the humid prairies from the west. The prairie dog is
a social creature living in colonies, and these, according to
Dr. Merriam,yf are sometimes from twenty to thirty miles in
length. The damage done to crops by these animals is enor-
mous, while their increase is greatly favoured by the spread
of agriculture. The cultivation of the soil enables them to
support larger families, whereas the cultivator further pro-
tects them by destroying their natural enemies.

The prairie dog inhabits a vast area between Montana in
the north and southern Texas in the south. Altogether seven
species of Cynomys are known, some of which range into
Arizona and Mexico, whereas none occur in the eastern or
extreme western States of America. No fossil remains of
Cynomys from Tertiary deposits have been identified, except
from the Miocene Republican River deposits of Kansas and
Nebraska, and even they only doubtfully belong to the genus.

* Depéret, Ch., “‘ Transformations of the Animal World,” p. 313.
+ Merriam, C. H., “ Prairie Dog,” pp. 258—263.

PRAIRIE DOGS 149

Cynomys, however, is certainly of American origin, though
some of its near relations, as T have shown, have probably an
Asiatic ancestry.

The coyotes or prairie wolves have been described as the
most inveterate enemies of the prairie dog. They are small,
graceful creatures hunting in packs like other wolves, but
living in burrows on the plains. Not long ago only a single
kind of coyote (Canis latrans) was recognised. More than a
dozen species are distinguished now; some of them on rather
slender grounds.* All these occur west of the Mississippi.
The presence of wolves in the Arctic regions of America has
been alluded to (p. 11 and p. 61), but I have not hitherto
made any remarks on their past history and origin.

The dog tribe (Canidae), to which all wolves belong, is
more widely spread in the world, that is to say, it has a larger
geographical distribution than any other family of carnivores,
one species being even found wild in Australia. Judging
merely from the extent of its range, the family Canidae should
be a very ancient one, and this assumption is fully borne out
by the knowledge we have obtained from fossil remains of the
dog tribe.

According to one of the most recent views, it would seem
as if the Cretaceous ancestors of the Carnivora, the great,
order to which the dog tribe belongs, were a group of small
arboreal mammals resembling the opossum in size and
habits, while more nearly allied to the primitive Insectivora.
The most. strictly terrestrial types, such as the Canidae and
Hyaenidae, have departed widely from the primitive skeletal
structure. In the Kocene we already find several families
of the Carnivora fully developed, one of which, the Miacidae,
is regarded by Dr. Matthew + as the precursor of the dog
family.

The latter originated in Oligocene times, but it was not until
the Miocene. Period that the genus Canis marked its first
appearance in America and Europe simultaneously. Since
it is highly improbable that the same genus should have arisen

* Merriam, OC. H., “ Revision of the Coyotes.”
+ Matthew, W. D., “ Carnivora and Insectivora of the Bridger,” pp. 328
—350,

150 ORIGIN OF LIFE IN AMERICA

independently in two different continents, the genus Canis
must have originated either in America or Europe. Dr.
Matthew* directs attention to the fact that the modern repre-
sentatives of the Canidae living in the Oriental region and in
South America are more akin to the Oligocene and lower
Miocene species than are the true wolves, jackals and foxes.
Assuming the original centre of evolution to have been some-
where in Europe or North America, we might argue that the
older types of dog-like creatures spread into distant parts and
were preserved there, while they were superseded in their
ancestral home by more modern types.

But we are apt to forget that the two species of Canidae
which live furthest from our hypothetical centre of origin
are most nearly related to what we generally look upon as the
most modern of the dog tribe. I am alluding to the wild dog
of Australia (Canis dingo) and to the Falkland island wolf
(Canis antarcticus). It is a most remarkable fact that the
latter is not nearly related to a single South American species
of the dog tribe, whereas it really belongs to the coyotes which,
as we have noticed above, are confined to western North
America. Similarly the Australian dog, which is now gene-
rally considered a truly wild species and not a recent human
introduction, is akin to one of the European Pleistocene dogs.
There is a wild dog in the mountains of Java (Canis teng-
gerana) which also appears to be nearly related to the dingo
of Australia. These two anomalous cases do not seem to fit
in with any of the existing theories. Dr. Wallace + main-
tained that it must have been as far back as the Secondary
Kra of geological history that Australia was in actual con-
nection with the northern continents, and received from the
latter the ancestors of the present fauna. There was no
subsequent land connection, according to Dr. Wallace, so that
from that remote time until now the Australian lands have
thenceforth evolved the various Marsupial and Monotreme
types which we now find there.

It is evident that Dr. Wallace did not believe in the indi-
genousness of the Australian dog when he made these remarks,

_ * Matthew, W. D., “ Lower Miocene Fauna from Dakota,” p. 180.
t+ Wallace, A. R., “Geographical Distribution,” I., p. 465.

DISTRIBUTION OF RACCOONS 151

Yet even those who do are at a loss to account for its presence
in Australia. Professor Weber * favours a very early human
introduction, even in Pliocene times. I myself have been
unable to form a definite judgment on this subject.

The origin of the Falkland island wolf is in so far a very
much more difficult problem to solve, as none of the species
of the dog tribe living on the opposite mainland of South
America are at all nearly related to it. Dr. Wallace} and also
Mr. Lydekker ¢ express the opinion that the Falkland islands
were evidently connected with the mainland at no distant date.
Dr. Wallace believed that this wolf was closely allied to a
Patagonian species.

Later on (p. 430) I shall have some further remarks to
make on this subject. I only mentioned these two instances
of distribution to show the difficulties which we frequently
have to contend with.

The raccoon (Procyon lotor) is by no means a typical in-
habitant of the prairie, still as it occurs here and there and
is very characteristic of North America it may as well be
mentioned here. By nature a forest animal, the raccoon, with
its omnivorous propensities and great adaptability, easily ac-
customs itself to the most diverse surroundings, and as a
rule thrives and breeds well in confinement. It inhabits the
whole of the United States and southern Canada and belongs
to a family (Procyonidae) which is quite confined to North
and South America, and always has been. We need not hesi-
tate in this case in attributing its origin to America. The
raccoon family has the same ancestors (the Karly Tertiary
Miacidae) as the dog family, according to Dr. Matthew, § one
of the members of the former, Cercoleptes (Potos), being
actually the nearest in its skeletal construction to the Eocene
Miacidae. It has been stated by Dr. Matthew that the lower
Miocene Phlaocyon from Colorado is approximately, though
not exactly, ancestral to the raccoon; but in view of the fact
that both Dr. Ameghino and Dr. von Ihering || emphatically

** Weber, M., “ Der Indo-australische Archipel,”’ p. 40.

+t Wallace, A. R., “ Geographical Distribution,” II., p. 49.

{ Lydekker, R., “ History of Mammals,”’ p. 140.

§ Matthew, W. D., “Carnivora and Insectivora of the Bridger,” p. 331.
|| Ihering, H. von, “Siidamerik. Raubtiere,” pp. 159—160.

152 ORIGIN OF LIFE IN AMERICA —

support its being one of the dog tribe (Canidae), we should
hesitate before accepting the earlier opinion.

The genus Procyon, to which the North American raccoon
belongs, only makes its appearance in the Pleistocene Period.
Nevertheless, it is quite possible that cave deposits, such as
that described from McCloud River in California containing
the new species Procyon sinus, may eventually be placed in
the Pliocene series.* At any rate, the genus Procyon must
have existed before Pliocene times, and it seems to me prob-
able that it originated either in South America or in some
western lands which have long since subsided. Dr. von
Ihering + believes that the Procyonidae have undoubtedly
come from eastern Asia. Why he should think so I cannot
imagine, for neither recent nor fossil species are known from
that continent.

It is now generally admitted, as I mentioned already
(p. 95), that Central America assumed its present shape and
contours at some time during the Pliocene Period (compare
p. 243). As soon as this land bridge became habitable for
terrestrial animals, northern species are supposed to have
poured across it into South America. We possess strong
evidence certainly that a steady stream of southern animals
invaded the northern continent in Pliocene and even in
Pleistocene times and that northern ones piepeeden in reach-
ing the south.

The group of the so-called toothless mammals (Hdentata),
comprising the ant-eaters, sloths and armadillos, are almost
entirely confined to South America; and that epnititiens no
doubt is their original home. A few penetrated in some
mysterious manner to North America in Kocene times, as I
shall explain more fully in another chapter. Shortly after-
wards they seem to have become extinct again in North
America, for no traces of edentates have yet been discovered
in the succeeding Oligocene deposits. It is only in the
Miocene beds of North America that we again meet with
examples of this curious group. They were representatives
of the huge Megalonyx which is closely allied to a southern

* Gidley, J. W., “ Fossil Raccoon from Californian Cave.”
+ Ihering, H. von, ‘‘ Siidamerik. Raubtiere,” p. 160.

CAVES AND THEIR CONTENTS 153

genus. Megalonyx and Mylodon, ‘which follows in Pliocene
times, were giant ground sloths almost the size of elephants,
while Glyptotherium, another Pliocene species, had a great
shield-like bony armour covering the whole body. The plio
cene species were accompanied by a great peccary (Platy-
gonus), a llama of a very large size (Pliauchenia) and a
number of other interesting creatures, all of which have now
completely vanished from the northern continent.

In the succeeding deposits from the great plains and moun-

tain regions, which have been classified by Professor

Osborn * as belonging to the lower Pleistocene series, we
notice the remains of two large elephants (Hlephas columbi
and EK. imperator), a true camel(Camelus)and two other mem-
bers of the same family, the great peccary Platygonus and the
two large ground sloths, Mylodon and Paramylodon. The

rivers were tenanted by beavers, otters, musk rats and a

curious semi-aquatic creature about the size of a bear, called
Castoroides. Related to some of the groups of South American
rodents, the latter suddenly makes its appearance in the

a Pleistocene beds of eastern North America.

Now we come to the cave deposits, which I have alluded to

' already on several occasions, and which Professor Osborn
' includes in the middle Pleistocene or Glacial series. The
| Port Kennedy cave in Pennsylvania contains no less than
| four species of the great edentate Megalonyx, also a Mylodon,
| two kinds of sabre-tooth tigers, a Mastodon, four species of
_ peccaries anda tapir. In the Potter Creek cave of California
| were discovered, among others, four species of Megalonyx, a
ie camel and a Mastodon. Finally, the Conard fissure of
| northern Arkansas revealed two species of sabre-tooth tigers,
_ three kinds of peccaries and numerous small animals. Apart
_ from a few deer bones and the remains of the curious Symbos,

an animal allied to the musk ox, it contained no traces of large
ungulates. Their presence in the district adjoining the fissure

_ is, nevertheless, indicated by the sabre-tooth tigers.

What I wish to make clear is that huge creatures requiring

| an abundance of vegetable food poured into North America,
_ not only in Pliocene but also in Pleistocene times. Many

* Osborn, H. F,, ‘‘ Cenozoic Mammal Horizons,” p. 85.

|

154 ORIGIN OF LIFE IN AMERICA

other mammals apparently had their original home in this
continent. Peccaries and tapirs, which, as we know, require
a hot and moist climate, lived as far north as Pennsylvania
even during the time when vast glaciers were supposed to have
covered the whole of Canada and a substantial slice of the
United States. We are told that the fauna of this period
clearly reveals the state of the climate. If the remains of the
animals above referred to indicate anything, they show us un-
doubtedly that the climate was mild, with an abundance of
vegetation and animal life. In common with most other geo-
logists, Dr. Hay believes that the climate of the Glacial
Epoch must have been cold in North America, because he
assumes the certain existence of vast ice-masses at that time
even in New York, in Indiana and in Missouri. If we deal
with this climatic problem from an independent standpoint
and endeavour to reconstruct the conditions prevailing during
the Glacial ‘Epoch from purely faunistic evidence, our con-
clusions cannot point to the prevalence of an exceptionally
cold climate. Proof of the existence of a cold climate in the
United States during the Pleistocene Period seems to be fur-
nished, says Dr. Hay,* by the occurrence of the three genera
of mammals, Rangifer, Bodtherium and Symbos.

The name Bodtherium is now applied to an extinct large

sheep-like creature, viz., B. bombifrons, whose remains have —

been discovered in Pleistocene deposits of Kentucky. Accord-

ing to Dr. Kowarzik (see p. 7), Bootherium was probably —
the direct ancestor of the northern genus Ovibos, which has ~
never been found in any Pleistocene beds in the United States.
Bodtherium can scarcely be claimed as an exponent of a H
cold climate, because it has never lived north of the United ©
States. The latest discoveries seem to indicate that a number «
of sheep-like animals originated in the United States towards j
the latter part of the Pliocene Period, and left their remains —
in various parts of the country. Thus the extinct Hucera- .
therium, first identified by Dr. Sinclair and Mr. Furlong from —
a cave in California, and Preptoceras from another ge

cave, are both allied to Bodtherium and Ovibos. Hence Ovibos |
is the sole member of this group which has survived, having”

* Hay, O. P., *‘ On the Changes of Climate,” p. 372.

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ON REINDEER AND CLIMATE 155

succeeded in adapting itself to an arctic habitat. The avail-
able evidence is all in favour of a gradual advance having
taken place of those large sheep-like forms from a more
southern to a northern habitat during late Tertiary times.
Mr. Osgood* has now discovered another extinct relation of
the musk ox in the Yukon Territory of north-western Canada.
He first described it as Scaphoceros tyrelli (including Ovibos
cavifrons of Leidy in. the same new genus), and suggested
that Scaphoceros may be ancestral to Ovibos. According to
Mr. Barnum Brown, the name Symbos has now been substi-
tuted for Scaphoceros. Hence Symbos is known from Indian
Territory, -Iowa, Missouri, Ohio, Pennsylvania, Kansas,
Arkansas, from Yukon Territory and from Alaska. Yet even
its former presence in Alaska cannot stamp Symbos as a cold-
loving animal, for close to its remains were dug up those of
a Mastodon, and who would be prepared to argue that the
Mastodon is an indicator of a cold climate ?

Lastly, Dr. Hay claims that the reindeer (Rangifer) having
occurred so far south of its present habitat (Fig. 10) in
Pleistocene times is a proof of the existence of a cold climate
at that time in the United States. I have discussed this pro-
blem once before (pp. 8—6), but I may add a few remarks.
If the drift area of North America had been covered largely by
the sea, as I believe it was, during part of the Glacial Epoch,
the country which was still habitable for the reindeer must
have been greatly reduced. Hence a southward emigration
was the only possible chance of survival for some herds of
reindeer. Driven out of their home by the stress of circum-
stances, they would have passed into a district, even if the
latter had been unsuitable to their requirements. At any rate,
we know that reindeer can live perfectly well in a temperate
climate and that they still inhabited Scotland in the twelfth
century long after the Glacial Epoch had passed away. I
cannot therefore consider its former presence in the United
States a proof of a cold climate. That it could only have
penetrated south in small numbers is indicated by its
total absence from all the North American caves hitherto
examined except one, and from almost all the other Pleisto-

* Osgood, W. H., ‘‘ Scaphoceros tyrelli,” p. 178.

156 ORIGIN OF LIFE IN AMERICA

cene deposits. On the other hand, we have noted that pec-
caries lived in the United States during the Pleistocene and
the preceding geological periods. They were not exterminated
by the severity of the climate. Representatives of the peccary
family not only survived the Glacial Epoch, they even showed
their indifference to it by invading the area which had only
just been forsaken by the supposed Wisconsin glacier, for
their remains, as Dr. Hay tells us, were found in deposits
overlying the Wisconsin drift at three different localities.
In the single cave in which the reindeer occurred its re-
mains were mingled with those of a species of peccary
(Tayassus tetragonus) very closely allied to that still living
in the Southern States and in South America. Nor was the
Glacial Epoch any more trying to the great ground sloth,
Megalonyx, for it also survived it and invaded the area covered
by the drift. The remains of a species of that giant edentate
were found some years ago, according to Dr. Hay, in an old.
filled-up pond, just within the alleged outermost moraine of
the Wisconsin glacier near Millersburg in Ohio. My own
views as to the nature of the climate prevailing during the
Pleistocene Period, and particularly during that phase of it
known as the “ Glacial Epoch ”’ or Ice Age, are derived from
a careful scrutiny of the living and extinct fauna and flora.
This study of the animals and plants does not reveal to me
that the Pleistocene Period was a period of extreme cold.
On the contrary, as I remarked before, the climate seems to
have been milder in a large portion of the northern
hemisphere than it is at present. An apparent increase of
temperature after the passing away of the “Ice Age”’ is
supposed to be indicated by the appearance of forms of animal
and plant life requiring a higher temperature than is com-
patible with the arctic condition believed to have prevailed
during the height of the Glacial Epoch. It is really due, I
think, to that perfectly natural re-occupation of tracts of
country on which both plants and animals had been destroyed.
The destructive agent, in my opinion, was not ice but water.

Glaciers no doubt existed on all the higher mountains near
the Atlantic and Pacific coasts. They owed their presence,
however, not to cold, but principally, as I mentioned before,
to the higher temperature of the eastern and western oceans,

HELICINA IN NORTH AMERICA 157

Towards the latter part -of the Glacial Epoch, when the
existing geographical conditions of the northern lands were
gradually brought about, the temperature of the Atlantic and
Pacific Oceans decreased, causing a diminution of precipita-
tion on the continents. With slight climatic oscillations the
conditions almost all over the northern hemisphere gradu-
ally seem to have grown less favourable for the survival of
Tertiary animals and plants than they were during the Ice
Age. Warmth and moisture-loving species are almost every-
where being replaced by others that can support greater
extremes of temperature, and the former only exist here and
there in diminishing colonies as relicts of the past. _

In the United States we have evidence of such a course of
events, not only among the higher groups such as the
mammals; some of the more slowly-moving invertebrates
are even more trusty indicators of the past geological history
of the country.

Three species of an operculate snail belonging to the family
Helicinidae inhabit the United States. One of them(Helicina
chrysocheila) occurs in Texas near the mouth of the Rio
Grande. Another (H. orbiculata) has a wide range from
Florida and Texas as far north as Arkansas and Tennessee.
A third (H. occulta) lives in isolated colonies among loose
leaf-mould in well-wooded districts from Carolina to Wis-
consin and Minnesota. Though inhabiting States where
severe winter frosts are common, it is amply protected against
them by its mode of.life. Mr. Cooke* maintains that all
operculate land mollusks are exceedingly sensitive to cold,
and that the whole group is undoubtedly a product of tropical
or semi-tropical regions. This view is borne out by the range
of Helicina. Far to the west of North America, beyond the
Pacific Ocean, a few stragglers occur in Burma and on the
Nicobar islands. As we.advance eastward they increase in
number in certain parts of southern Asia. Almost throughout
Polynesia we meet with some species, and also on the West
Indian islands (Fig. 11). That the genus is a very ancient
_ one must be evident from its geographical distribution. It had
ig already reached America in early Tertiary times, for Dr. Dall

* Cooke, A. H., ‘‘ Molluscs,” p. 24.

158 ORIGIN OF LIFE IN AMERICA

describes a species from the Oligocene Silex beds of Tampa
in Florida apparently related to a Helicina still inhabiting
the Bahama islands. Considering that the genus Helicina is
almost confined to tropical and semi-tropical countries, we
may assume that it spread northward at a time when very
mild climatic conditions prevailed in the northern United
States, and that a few more hardy species have survived in
isolated colonies wherever they could obtain sufficient pro-
tection against frost. This view is confirmed by the fact
that Helicina occulta, now an extremely rare shell, is abun-
dant in the Pleistocene loess beds of Indiana, Iowa and
Nebraska. Mr. Shimek * likewise expressed the opinion that
the still existing northern colonies of Helicina occulta ap-
pear to be the remnants of a once common race which is
evidently dying out.

A family which resembles the Helicinidae, in so far as it is
largely confined to tropical and sub-tropical regions, is that
of the Phasmidae.t They comprise orthopterous insects of
the shape of a small twig, and hence are known as “ walking
sticks,’ also “ prairie alligators ”’ or “ stick-bugs ’’ in America.
All the species found in the United States are wingless. They
are thus not liable to accidental transport except perhaps by
water. All are vegetable feeders, and over a dozen kinds
inhabit the southern States. Among these walking-stick
insects there is one which has a remarkably northern range,
viz., Diapheromera femorata. I met with it on Goat Island,
above the Niagara Falls. It has also been observed near
Toronto, and several other places in southern Canada. We
possess no fossil evidence of the geological history of the
genus Diapheromera; nevertheless, the fact that the family,
Phasmidae was already represented in Jurassic times, accord-
ing to Dr. Handlirsch,{ justifies the assumption that Dia-
pheromera originated and began to spread northward in pre-
Glacial times, and that it may be regarded as a southern relict
in its present northern habitat. |

Two well-known instances of survivals of southern species

* Shimek, B., ‘‘ Helicina occulta.”
t+ Caudell, A. N., ‘‘ The Phasmidae of the United States,” p. 874.
{t Handlirsch, A., ‘‘ Die Fossilen Insekten,” p. 1191.

Fig. 11.—Map of North and South America, showing the distribution (in black and
within the area surrounded by small circles) of the snail Helicina,

a

[ Zo face p. 158.

TURKEYS AND PARROTS 159

of birds in northern habitats occur to me. Strictly speaking,
they should not be quoted, because they are now extinct in
their northern habitats. But as their extermination happened
within historic times, and has been caused by human interfer-
ence, I may venture to include them in this group of southern
invaders. They are the turkey and the Florida parrot.

The wild turkey (Meleagris gallopavo) belongs to a dis-
tinctly southern group of birds. In the time of the early
settlers it was common as far north as Massachusetts, and
extended westward to Colorado and southward to Mexico and
Florida. Being a much-prized luxury of the pioneer hunter,
it was soon exterminated in the more populous districts. It
still occurs in some of the southern States, while an allied
species is known from Central America, The genus Meleagris
was already an inhabitant of North America in Oligocene
times, for Professor Marsh described a species from the White
River deposits in Colorado. No doubt it has lived in North
America ever since those early Tertiary times. All we know
from fossil evidence is that the remains of two other species
were identified from Pleistocene deposits in New Jersey, while
the bones of the wild turkey itself have been noticed in a cave
in Pennsylvania. Like the edentates and peccaries this
southern genus of birds flourished in the northern States
throughout the Glacial Epoch and survived there until his-
toric times.

The Florida parrot (Conuropsis carolinensis) is the only
example of the large parrot tribe indigenous to the United
States. It is now restricted to the comparatively small area
of the Gulf States and the lower Mississippi Valley. Yet the
early settlers noticed this bird even near the shores of the

4 _ Great Lakes, and occasionally it was observed near the cities

that were springing up in the eastern States. No doubt it
survived in these northern districts from remote times, al-
though we possess no fossil evidence of this fact. It cannot
be contended that the parrot left its former habitat through
persecution ; nevertheless, man in his agricultural pursuits,
must have interfered with it, possibly by reducing the birds’
food supply.

I wish now to make a few remarks on the sla bitamin of
the mighty river and its tributaries flowing through the

160 ORIGIN OF LIFE IN AMERICA

continental basin, as they are of such importance in tracing
the geological history of the fauna. The Mississippi lies
wholly within the boundaries of the United States, and drains
more than two-fifths of their area. Originating in Lake Itasca
in Minnesota, the Mississippi receives during its long course
four great tributaries, the Missouri, Ohio, Arkansas and Red
River, and a large number of smaller ones. The two prin-
cipal groups of animals inhabiting this great river system are
the fishes and fresh-water mussels. Some of the fishes are
able to live in brackish water, others spend part of their
lives in the sea, so that they are not of such extreme im-
portance from a zoogeographical point of view as the fresh-
water mussels.

Fresh-water mussels, or Naiades as they have been called,
all die quickly if immersed in salt water or if removed to thie
land. Their distribution being world-wide, they have been
looked upon by some naturalists as among the best indicators
of former changes of land and water over the globe. Others
have urged that the wide range of these mussels may be due to
accidental conveyance by birds or fishes. It was thought
that the eggs or the newly-hatched fry of the mussels had
been thus transported. Many species immediately after their
fry has been hatched from the eggs, develop hooklets on the
temporary shell, by which the young mussels can attach
themselves to foreign objects. It has been argued that such
larval mollusks might become attached to the feet of aquatic
birds and be carried by them in their flight from the fresh
waters of one region to those of other regions and there be set
free. Theoretically, such an accidental transport would seem
quite a possible one from time to time, certainly much more
likely than a similar conveyance of the fry by fishes from; one
river system to another. In a country like North America,
where millions of migratory birds pass annually north and
south, and to some extent east and west, the effects of a con-
veyance such as suggested should be clearly discernible in the
composition of the North American fresh-water mussel fauna.
Yet although there are over four hundred different kinds of
fresh-water mussels in the Mississippi drainage area, some
of them having existed there almost unchanged since Cre-
taceous times, the fauna to the east and west of that area is

<<. "so s

FRESH-WATER MUSSELS 161

entirely different.* The geographical distribution of fresh-
water mussels in North America thus constitutes a practical
demonstration of the correctness of the view so ably main-
tained by Dr. von Ihering,t and supported by Dr. White,
that these mollusks are not appreciably affected by chance or
accidental dispersal.

The family Unionidae, to which all the North American
fresh-water mussels belong, first appeared during the Triassic
Age. Their principal diffusion over the globe may possibly
have been effected in Secondary or Mesozoic times. During
the closing period of the Mesozoic Era, the Cretaceous, the
family attained an extraordinary development, particularly
in the Laramie strata. The remarkable feature is that many
of the species in these beds are so nearly like the living
species that according to Professor Whitfield £ they are to all
intents and purposes the same. There were at that time
(the Cretaceous Period) two great land masses in place of the
North American continent viz., one in the east, the other
in the west. The fresh-water mussel fauna occupied then
as far as we know, mainly the eastern flank of the western
land-mass. The latter was probably connected, as I shall
endeavour to show later on, with some old land-masses on
the west coast of South America. South America may thus
have acquired its Unionidae in Mesozoic times.

The two great families of fresh-water mussels, Unionidae
and Mutelidae, have been recognised for some time past, also
the restriction in distribution of the latter family to Africa
and South America. It was not until the year 1891 that
Dr. von Ihering § made the striking discovery that all the
Unionidae begin their existence on hatching from the egg, as
so-called “‘ glochidium ”’ larvae, while the Mutelidae have an
entirely different ‘‘lasidium’’ larva. The Unionidae, of
which about one thousand species are now known, have since
been subjected to a thorough critical revision by Dr. Simp-

* White, Charles A., ‘‘ Ancestral Origin of North American Unionidae,”
pp. 77—79.

t Ihering, H. von, “‘ Najaden von 8S. Paulo,”’ pp. 133—140.

{t Whitfield, R. P., ‘‘ Fossil Unionidae from Laramie Clays,”’ p. 624.

§ Ihering, H. von, ‘‘ Anodonta and Glabaris.”

L.A. M

162 ORIGIN OF LIFE IN AMERICA

son,* as a result of which we now recognise sixty-one
genera.

To return to fie strictly North American fresh-water
mussels, it has been found that a common assemblage
inhabits the entire Mississippi drainage basin, and that a
considerable number of the species have a distribution cover-
ing the greater part of this area, as well as ‘the whole of
Texas and even parts of eastern Mexico. The streams which
fall into the Atlantic are peopled by an entirely different set
of forms, the Appalachian chain seeming, according to Dr.
Simpson, to act as a sharp barrier between the two regions.
In the greater part of Mexico and Central America a totally
different fresh-water mussel fauna is found. ‘Two Unios,
one Margaritana and some half-a-dozen Anodons, are all that
have hitherto been credited to the immense region on the
Pacific slope of North America. One of the Unios, says
Dr. Simpson,y has been recorded in error, the other is a
form of the most abundant and most widely distributed Unio,
viz., U. luteolus. The causes which led to this striking
difference between the fresh-water mussel fauna of the
Central basin and that of the Pacific slope will be discussed
in another chapter. I may only mention that a somewhat
similar-disparity between the two faunas has been observed
among the fresh-water fishes. Before dealing with these
there is one other matter of importance that I should like
to refer to in connection with the geographical distribution
of fresh-water mussels.

The far-reaching results of the study of the geographical
distribution of such a group as the fresh-water mussels is.
exemplified in a striking manner by the following physio-
graphic problem. In discussing the origin and recent history
of the physical features of the southern Appalachians
Messrs. Hayes and Campbell advocated the theory that the
upper Tennessee river, now a tributary of the Ohio, formerly —
flowed into the Gulf of Mexico by way of the existing Coosa
and Alabama Rivers. The conclusions were based entirely

* Simpson, ©. T., ‘‘Synopsis of the Naiades.”’

+ Simpson, ©. T., “Relationship and Distribution of Unionidae,”
pp. 354—358.

BONY-PIKE AND BOW-FIN 168

4 upon physiographic evidence—such as the character of the

Tennessee-Coosa divide, the nearness of the gorge below
Chattanooga, and the general arrangement of the drainage
lines.* Now it is a remarkable fact that Dr. Simpson has quite
independently come to a similar conclusion from a study of
the fresh-water mussels. The upper Tennessee and also the
Alabama River abound in species of the genus Pleurobema,
which is quite absent in the lower Mississippi. The species,
moreover, found in these two rivers are very closely allied, so
that this and other characters led Dr. Simpsonf to the con-
viction that at some time in the middle or later Tertiary, the
Tennessee River must have flowed southward into some of
the streams of the Alabama drainage, discharging its waters
in this manner direct into the Gulf of Mexico.

In the fourth chapter (p. 88) I cited some ganoid fishes
of the Mississippi in illustration of the zoological relation-
ship existing between eastern North America and eastern
Asia. Two other well-known and very remarkable ganoid
fishes live in the Mississippi basin, viz. the bow-fin (Amia
calva) and the bony-pike (Lepidosteus osseus). The former
is-the sole surviving member of the family Amiidae. Long
ago, in early Tertiary times, the genus Amia inhabited middle
and western Europe, while it is amply represented in the
Eocene (Bridger) deposits of Wyoming. Bony-pikes lived in
Europe from Eocene to Miocene times. In America they
likewise appeared in the Eocene period, and persisted until
the present day. It is evident that both the bow-fin and bony-
pike are extremely ancient types, which have managed to
survive a great many geological changes of the American
continent. Their ancestors must have travelled to Europe
in the dawn of the Tertiary Era, assuming of course that
_ North America was the birthplace of these genera. Did
they travel from river to river and from lake to lake across
North America and Asia to Europe, or did they utilise the
fresh-water streams of a shorter direct land bridge to

Europe? These are problems to be solved. The zoological.

* Hayes, O. W., and M. R. Campbell, “ Relation of Biology to Physio-
_ graphy,” p. 131.
+ Simpson, ©. T., “ Evidence of Unionidae,”’ pp. 134—135.

mM 2

\

164 ORIGIN OF LIFE IN AMERICA

affinity between Europe and North America is so strong,
and already so many instances of this relationship have been
referred to, that nothing short of a wide and convenient land
bridge with lakes, rivers and mountains will suffice to ex-
plain the meaning of the palaeontological facts. All we know
is, that in early Tertiary times these fishes multiplied and
migrated from their original centre of dispersal. The genus
of the bow-fin is all but extinct. Only a single species
remains. The bony-pikes exhibit a little more vitality, no
less than three species being still living. The common form
(Lepidosteus osseus) ranges from the Great Lakes to Vermont
in the east, and from there south-westward as far as Mexico.
A much larger bony-pike lives in the southern States, in
north-eastern Mexico and in the island of Cuba, while a
smaller species (L. tropicus) has been observed in Tabasco,
Guatemala, Nicaragua and Panama.* If Lepidosteus were a
fish directly limited to fresh water, we might argue that at
some remote time in the past, a land mass extended from
Mexico to Cuba and southward to Panama, but being ocea-
sionally met with in brackish water it is possible that bony-
pikes can traverse short distances by sea. We cannot for this
reason base any conclusions regarding minor changes of land
and water on the present distribution of these fishes. Never-
theless it is a significant fact that the western States ‘are
devoid of bony-pikes and perches as they almost are of fresh-
water Unios.

Besides the Mississippi fauna, the curious dwellers of sub-
terranean waters in the Mississippi drainage area throw a
certain amount of light on the past conditions of the country.
A brief account of them at any rate will be of interest before
concluding this chapter.

I believe Mr. Putnam f was the first to exhibit a collection
of blind fishes and crustaceans from the Mammoth Cave to a
scientific meeting. In doing so he expressed the opinion
that most of the animals inhabiting the cave are of compara-
tively late introduction, since they are closely allied to forms

* Regan, ©. Tate, “ Biologia Centrali-Americana,”’ p. 181.
+ Putnam, F. W., “ Mammoth Cave and its Inhabitants,” pp. 194—
195.

BLIND ANIMALS 165

living in the vicinity of the cave. Nevertheless he claimed
for the blind fishes and some of the invertebrates a different
origin, because the former had no immediate relations among
fresh-water forms, while the lernean fish parasité was a
more decidedly marine than fresh-water form. He took these
facts to indicate that part of the great cave system was
supplied by marine life. .

Professor Packard * makes no allusion to Mr. Putnam’s
view in his account of the origin of the subterranean fauna
of North America. Mr. Putnam’s theory indeed appears to
be searcely tenable. His remark that the blind fishes of the
Mammoth and other caves have no immediate relations among
fresh-water forms has to be modified in accordance with our
existing knowledge of fishes. The blind fishes, all of which
belong to the family Amblyopsidae, are no doubt a very
ancient group, and, as Drs. Jordan and Evermann7 suggest
they are probably descendants of the eyed genus Chologaster,
or at least forms very closely allied to it. Now one species
of Chologaster inhabits swampy marshes in the southern
States, and two others live in the subterranean streams of
Tennessee, Kentucky and Illinois. The most typical blind
fishes, T'yphlichthys subterraneus and Amblyopsis spelaeus,
are met with in the underground streams of Indiana and
Kentucky.

Professor Garman { expressed the opinion that the blind
species observed in the caves-were already blind prior to the
formation of the caves, and that they only collected there
from various directions owing to the favourable conditions
for their requirements. Whether this theory is based on sound
evidence need not be discussed, but his statement that
Typhlichthys subterraneus has a very wide range has been
questioned by Professor Higenmann,§ who showed that the
apparently identical species from Missouri is really quite
distinct from that of the Mammoth Cave. Professor Higen-
mann points out that we have to deal with a remarkable and

* Packard, A. S., “ Origin of subterranean fauna.”’

tT Jordan, D.8., and B. W. Evermann, “ Fishes of North America,”
Vol. I., p. 702. .

{ Garman, H., “ Origin of Cave Fauna,” pp. 240—241.

§ Eigenmann, C. H., “ A Case of Convergence,” p. 281.

% 7 S

166 ORIGIN OF LIFE IN AMERICA

instructive case of convergence. The two very distinct forms
have converged because of the similarity of their environ-
ment, and especially owing to the absence of those elements
in their environment that lead to external protective
adaptations.

- The family Amblyopsidae is confined to North America,
and its nearest relations are no doubt the Poeciliidae, a group
of fresh-water fishes with a wide distribution in America,
southern Europe, Asia and Africa. There are therefore no
grounds for the supposition that the blind fishes of the sub-
terranean waters of North America are seseonded from
marine ancestors.

CHAPTER VIII
THE SOUTH-EASTERN STATES

Tue inhabitants of the south-eastern States, which I shall
endeavour to describe in this chapter, form, in many respects,
a great contrast to those of the continental basin. The greater
humidity of the Atlantic States produces that characteristic
wealth and profusion in floral life which constitutes so at-
tractive a feature as we approach the ocean from the west.
And no one can fail being struck by the change in vegetation
even in travelling southward through the Atlantic States from
the north. The oaks, chestnuts and hickories become more
varied, evergreens of all kinds increase in number, new and
magnificent magnolias make their appearance, while vines
and creepers mingle their foliage with that of shrubs and
trees. The splendid white pine of the north is replaced in
the south by the long-leaved yellow pine, whose hard, strong
and durable wood serves such a wide range of uses. . We also
notice an entirely new conifer, the cypress, which, like the
tamarack, sheds its leaves in the autumn. Further south in
Florida, still greater changes await us, and in the extreme
tip of that peninsula we are surrounded by tropical vegeta-
tion. Low fan palms and the palmetto grow even further
north, but here we meet for the first time with the royal palm,
which for height and grace of shape is unequalled, and many
other characteristic denizens of the tropics. Indeed, as Mr.
Brendel * points out, the flora of southern Florida should not
be looked upon as part of the North American flora but as a
link between it and that of the West Indies. Over two hundred
and thirty species of plants do not extend north of Tampa,
whereas southern Florida has one hundred and eighty seven
in common with the West Indian Islands.

This affinity between the floras of southern Florida and

* Brendel, F., ‘‘ Notes on the Flora of Florida,” p. 449.

ce,

168 ORIGIN OF LIFE IN AMERICA

the Antilles is generally believed to be due to accidental dis-
persal. The seeds of these plants are supposed to have been
conveyed to southern Florida from the West Indian Islands
by winds, ocean currents or migratory birds. Professor
Engler,* for instance, argues that a direct land connection
between the West Indies and North America by way of Florida
could never have eixsted, because the latter had been sub-
merged beneath the sea until the end of Tertiary times,
and that seeds are easily conveyed to Florida by the branch
of the Gulf Stream sweeping along the northern shore of
Cuba in a north-eastward direction, carrying quantities of
vegetable matter and often even tree trunks. Winds could
only transport such seeds that are specially adapted for long
_ flights. As regards migratory birds, which are popularly
believed to carry seeds to great distances in their crops
and among their feathers, it may be pointed out that
the main highway for birds travelling between the eastern
States and South America is by way of north-western
Florida and Cuba, and not by southern Florida.; If
birds had any special influence in the transport of seeds, not
the southern portion of Florida but the northern one should
show affinities in the flora with the West Indies. If the
resemblance in the vegetation of southern Florida and the
Antilles were mainly due to the Gulf Stream, we should expect
to find the most pronounced similarity between the two floras
among the strand plants of Florida. This is not the case.
The great majority of the flowering plants now known to be
common to the West Indies and North America occur in what
is called the “ hummocks” of the southern extremity of
Florida. ‘These hummocks consist of isolated groups of hard-
wood trees, shrubs and vines, and are scattered like islands
in the everglades and pine forests, instead of being surrounded
by the ocean. Moreover, the flora of southern Florida is by
no means exclusively West Indian in character. About forty
species of plants are peculiar to southern Florida, and over
twenty are found elsewhere only in Mexico.t{

* Engler, A., “ Entwicklungsgeschichte d. Florengebiete,” IL, p. 215.

t+ Cooke, W. W., “New Facts about Migration of Birds,” p. 376.

{t Harshberger, J. W., ‘‘ Floristic Elements of Eastern North America,”
p- 612.

VEGETATION OF FLORIDA 169

A West Indian fauna, too, is associated with the flora in this
portion of the United States, as will be shown later on. The
problem presented by the origin of this tropical element in
the North American flora at any rate is not quite so simple
as it appears at first sight. Dr. Harshberger is of the opinion
that the hummock lands on which the tropical flora principally:
grows represent part of an ancient system of islands which
existed at a time when the Gulf Stream passed right across
the then submerged portion of northern Florida. We might,
therefore, make further enquiries as to whether this theory is
supported by geological or other evidence, before taking for
granted that the tropical element in the fauna and flora of
Florida is of purely accidental origin.

Professor Shaler * informs us that along the coast of
Florida, both on the eastern or Atlantic and the western or
Gulf side, there arise from beneath the sea a number of
submarine springs. They thus discharge great tides of fresh
water, originally gathered on the land, through openings on
the floor of the ocean. He argues that these springs probably
shed their waters along the margin of the sea above high water
level, and remarks, ‘“‘I cannot conceive any such under-
ground waterways to have been produced under the existing
conditions of land and water.” Heassumes consequently, that
Florida, or a certain part of it at any rate, must have stood
at a higher level in relation to the sea than it does now within
comparatively recent geological times.

Through the discovery of a submerged system of drainage-
valleys off the coasts of Florida and fhe Antilles, Dr.
Spencer is led to believe in an elevation of this area during
the earlier part of the Pleistocene Period to the extent of
8,000 to 12,000 feet or more. During a subsidence which
followed, according to the same author, the greater part of
the existing peninsula of Florida was submerged. Dr.
Spencer ¢ does not specify what parts of it remained above
water, but presumably the whole of the southern Florida
which is low-lying was included in the submerged portion. If

* Shaler, N.S., “Nature and Man in America,” pp. 104—106.
T Spencer, J. W., “ Reconstruction of Antillean Continent,’’ pp. 128—

129.

170 ‘ORIGIN OF LIFE IN AMERICA

the tropical flora had gained admission to southern Florida
during its supposed land connection with the West Indies
in lower Pleistocene times, it would have been all destroyed
again subsequently. If Dr. Spencer’s theory were substan-
tiated, the tropical flora of Florida should owe its origin to
accidental transport.

When Dr. E. A. Smith * visited Florida in 1880 he made
some geological notes on the peninsula which do not bear out
Dr. Spencer’s views. He maintains that Florida was elevated
_ nearly to its present height above sea-level after the deposi-
tion of the Vicksburg limestone, that is to say, after the
Eocene Period, and that this elevation persisted until the
Pleistocene, when the country was partly submerged.

No one, however, has done more practical geological work
on the peninsula than Dr. Dall,+ who, in his monumental
treatises on the Tertiary fauna of Florida, presented us with
a masterly survey of the past life of that portion of the United
States. His opinion on the geological history of Florida
deserves, therefore, most serious consideration, and it may be
stated at once that he is strongly opposed to Dr. Spencer’s
views, declaring them to be “ incompatible with every geologic
and palaeontologie fact of South Florida which has come to
my knowledge.”

As the result of his researches Dr. Dall expresses the
opinion that the peninsula of Florida, together with the larger
Antillean Islands and the Middle American highlands, were
uplifted, and the two Americas thus united in Oligocene
times, that is to say, during the early part of the Tertiary
Era.

Professor Gregory { had a similar idea, except that he did
not specify any geological period.

When Florida again became disconnected from this Antil-
lean continent is not clearly stated, but Dr. Dall thought
that it formed a peninsula of the southern continent as it.
does now of the northern. Florida, according to the same
author, became definitely united to North America towards

* Smith, E. A., “Geology of Florida,” p. 306.
+ Dall, W. H., ‘‘ Tertiary Fauna of Florida,” IV., p. 1546.
| Gregory, J. W., “Geology of West Indies,” p. 309.

GEOLOGICAL HISTORY OF FLORIDA 171

the end of the Miocene Period, while a slight depression
occurred in Pliocene times, and little change since. Whether
the tropical flora of southern Florida, or part of it at any rate,
is the relict of an Oligocene invasion from the south is left
undetermined by Dr. Dall’s researches. Yet, from the fact
that a species of the terrestrial mollusk Glandina occurs in
the Pliocene Caloosahatchie beds of south-western Florida,
we might be led to infer that other southern forms might
have survived on the peninsula till Pliocene and possibly
recent times.

Dr. Hill coneurs in so far with Dr. Dall’s conclusions
as he establishes in Jamaica signs of a tremendous orogenic
movement in late Oligocene or Miocene times, resulting in an
uplift whereby many of the West Indian Islands and pos-
sibly an insular southern portion of Florida became united
with one another. In Miocene or early Pliocene the islands,
according to Dr. Hill,* were severed from one another by
submergence, assuming gradually their present outlines which
they have since retained.

That some kind of union of the island of Florida with the
West Indies took place in Miocene times is likewise indicated
by Dr. Matthew f in his attempt to delineate the hypothetical
outlines of the continents in Tertiary times, for he distinctly
unites southern Florida and Cuba by land.

According to Dr. Vaughan,{ the Florida plateau already
existed in pre-Oligocene times, but it was only towards the
end of the Oligocene Period that a portion of the plateau rose
above the sea and apparently remained so ever since.
Although this constituted only a small island (“ Orange
island ’’ as he calls it), the deposits of the whole plateau are
full of sand and arenaceous material implying proximity of
land.

From the opinions cited on the geological history of Florida
it is evident that there is nothing distinctly antagonistic to
the view that part of the tropical flora of southern Florida
is a relict from Tertiary times, many of the species being

* Hill, Robert T., “Geology of Jamaica,” p. 224.
+ Matthew, W. D., “ Continents in Tertiary Times,” p. 366.
{ Vaughan, T. W., “ Geologic History of Floridian Plateau.”’

172 ORIGIN OF LIFE IN AMERICA

probably the descendants of those which passed northward
from the Antilles at a time when a land connection (possibly
in Oligocene times) joined the latter with the old island of
Florida. The fauna of Florida lends some support to this
view. At any rate, it gives us more solid foundations for
estimating the nature of the physical changes which the —
peninsula has undergone within more recent geological times.

In the last chapter I alluded to a species of parrot
(Conuropsis carolinensis) which in historic times still ex-
tended its range as far north as the Great Lakes, and which
seems at present to be retreating towards its original centre
of dispersal in the south-east. Now this Carolina parrot,
as it is generally called, has no near relations. Its
closest ally, Conurus, is a genus of parrot ranging from
Paraguay and eastern Bolivia in the south to Mexico
and the West Indian Islands in the north. The fact
of its occurrence in the West Indies alone implies that it is
an ancient genus, for these islands have undoubtedly been
separated from the continent for a long time. Moreover,
Cuba, Haiti, Mona Island off Porto Rico, Jamaica and St.
Thomas all possess distinct species of Conurus. It seems not
unlikely that Conuropsis is an eastern offshoot of the older
Conurus, just as Rhynchopsittacus has originated from it in
the west. The occurrence of this parrot on the mainland does
not necessitate the former existence of a land bridge to the
West Indies, but, if other facts point to it, the presence of the
Carolina parrot in the south-eastern States and its subsequent
invasion of the northern States is more readily explained
by it.

I also made allusion before to the newt Spelerpes, a genus
confined to America and southern Europe. One of its peculiar
characters is that its tongue can be jerked out toa considerable
distance. Only one other newt peculiar to Florida and Caro-
lina, viz., Manculus, agrees with Spelerpes in the nature of
its tongue, and, like it, must be an ancient genus. Another
very peculiar amphibian is Amphiuma means, an eel-like
creature with tiny limbs, inhabiting the ditches of rice-fields
and swamps of the south-eastern States. No fossil remains
of this interesting species are known, but there can be no
doubt that it is a very old form. Pseudobranchus lateralis, —

REPTILES OF FLORIDA » S4T8

another most primitive amphibian, is likewise confined to
the south-eastern States, while Siren lacertina has its head-
quarters in the same region. A very striking amphibian is
the Florida tree frog (Hyla gratiosa), the largest tree frog of
North America, which is common in Florida, extending from
there across the borders of Georgia and Mississippi.

The most remarkable member of the fauna of Florida, from
a zoogeographical point of view, is one of the worm-lizards
(Amphisbaenidae). The Florida worm-lizard (Rhinema
floridana) is a limbless, blind, worm-like creature which
spends its entire existence under ground. It is no doubt of
immense antiquity, and the only member of the family known
from North America.

Whether the curious glass-snake (Ophisaurus ventralis) has
originated in the south-west or south-east is a difficult pro-
blem which future researches may help to solve. Professor
Cope * speaks of an eastern and western type, and it may
possibly have spread northward from two independent centres.
I need scarcely mention that the glass-snake, like the Huro-
pean slow-worm, is a limbless lizard. Anyone may convince
himself of this fact by examining the eyes, which possess
well-developed eyelids, while the presence of ear openings
also distinguishes these creatures from true snakes. ° The
particular point of interest in the presence of the glass-snake
in America lies in the circumstance that a closely allied
species (O. apus) inhabits Maroceo, the Balkan Peninsula
and Asia Minor, while a second glass-snake is known from
the eastern Himalayas and Burma. This extremely discon-
tinuous range denotes great antiquity. The glass-snakes,
moreover, live principally underground, and, like the worm-
lizard, are not liable to accidental conveyance by any of the
occasional means of dispersal that we hear so much of. Their
occurrence on both sides of the Atlantic gives great weight
to the evidence, cited in previous chapters, of the former exist-
ence of a land bridge right across the middle of the Atlantic.
I need not discuss the subject any further now, because it will
be amply dealt with in some of the succeeding chapters, when
new arrays of facts in support of my contention will be sub-

* Cope, E. D.,-“ Crocodilians, Lizards and Snakes,’’ p. 496.

174 ORIGIN OF LIFE IN AMERICA

mitted. We may as well collect the facts tending to support
this theory as we proceed, since a great accumulation of
material in one place might appear wearisome.

The distribution in America of one of the genera of earth-
worms (Diplocardia), on which glass-snakes largely live,
somewhat resembles that of the glass-snakes in America.
There is a species in Florida and three in Carolina. Further
north the genus appears in Illinois and Nebraska and we also
have a couple of species in Mexico and Lower California.

It was Professor Adams,* I think, who first directed atten-
tion to the presence of two very distinct and powerful centres
of dispersal, one in the south-east and one in the south-west.
Although I am by no means so impressed, as Professor
Adams and Dr. Brown are, by the significance of the south-
eastern centre of dispersal as compared with the south-
western one, which is incomparably more important, I quite
concur in their opinion that the former faunistic centre is
perfectly recognisable. These writers moreover discuss the
problem which I have dwelt upon so many times above, viz.,
that of the climate during the Ice Age.

Having adopted the current views of the existence of giant
glaciers in the northern United States accompanied by
an arctic climate Professor Adams + and Dr. Brown { were
obliged to search for suitable “ biotic preserves” where the
pre-Glacial fauna could have safely weathered the Ice Age.
These they discovered in the two centres of dispersal alluded
to, in the south-east and south-west, and from them they sup-
pose the waves of migrants to have streamed forth northward
after the Glacial Epoch was over. The presence of a few
stray remains of northern animals south of their present
habitat lent a certain amount of credence to the theory in a
southward extension of the arctic climate. But we must
remember that these northern creatures, when actually
pressed out of their boreal home by a restriction of
their habitats, found themselves in the northern United

* Adams, ©. C., “South-Eastern States as a Centre of Distribution,”
p. 121.

+ Adams, ©. C., “ Post-Glacial Dispersal of North American Biota.”

{t Brown, A. E., ‘ Post-Glacial Nearctic Centres of Dispersal.”

CENTRES OF DISPERSAL 175

States among an almost semi-tropical fauna of colossal
sloths, peccaries and other southern forms that have long
since vanished, and which lived through it all in close proxi-
mity to the supposed ice-sheets and arctic climates. The great
majority of the Pleistocene deposits in the north indicate that
the country had a milder climate during the Ice Age than at
present, and this is particularly shown by those containing
plant remains. As plants are supposed to be more trust-
worthy guides than animals, as indicators of former climatic
conditions, I will give one more example of a Pleistocene
deposit from the southern States which has come to my know-
ledge. :

A Pleistocene deposit in north Carolina examined by Pro-
fessor Berry * yielded no boreal or even cool temperate
plants. Hence it may safely be concluded, he thinks, that
the temperature of the Pleistocene Period in the same latitude
was not lower than it is now. If anything, he says, it was
slightly higher. Additional facts pointing to the same general
conclusion are the former more northward extension of the
cypress (Taxodium distichum) and of Planera aquatica. That
these plants did not flourish during mild inter-Glacial phases
of the Glacial Epoch, remarks Professor Berry, is indicated
by their being associated in Maryland with ice-borne boulders
of considerable size.

To return once more to southern Florida, we find that what
we observed among plants, namely, the tropical element, is
likewise recognisable in the fauna. According to Dr.
Merriam + the semi-tropical insect fauna of southern Florida
comprises in all not less than a thousand species of Antillean
insects, half of which are beetles.

Among the mollusks there are a number of Antillean genera
represented in southern Florida, such as Chondfropoma,
Liguus, Cepolis, Varicella, and others spoken of by Dr.
Pilsbry as Mexican genera, such as Eglandina, Praticolella
and Drymaeus (dormani type). Dr. Pilsbry regards only the
last group as genuine natives of the soil. He believes that
their ancestors entered Florida at the close of the Miocene

* Berry, E. W., “ Pleistocene Flora of Carolina,” p. 347—348.
+ Merriam, ©. H., ‘ Distribution of Life in North America,” p. 53.

176 ORIGIN OF LIFE IN AMERICA

Period by a land passage, but does not state clearly whether
they came by a more direct route than exists at present. All
the other snails are considered by Dr. Pilsbry * to be waifs
and strays derived from Cuba and the Bahama islands, by the
agency of hurricanes, drifting trees and the like.

I do not know why Dr. Pilsbry should make this reserva-
tion in favour of Drymaeus, as one of the species found in
southern Florida (D. dominicus) is also known from Haiti
and Cuba, besides the Mexican habitat. On the other hand,
we must not forget that Dr. Dall + discovered a number of
species of the land-snails Bulimulus and Cepolis in the
Oligocene Silex beds of Tampa in Florida. Both of these have
come from the south, for Bulimulus, though extinct in
Florida, still lives on the island of Fernando de Noronha in a
species almost indistinguishable from one of the Floridian
ones. Cepolis still inhabits Florida, but is not found else-
where in the United States. It has its headquarters in the
West Indies, and was a European resident, according to
Sandberger, in early Tertiary times. Of the land snail genus
Oxystyla, allied to Drymaeus, the species O. undata has a wide
range in the West Indies, and is also known from southern
Florida. Yet the Floridian specimens both belong to varieties
peculiar to the peninsula.{ Similarly, the Cuban varieties
of Liguus fasciatus are not the same as occur in Florida.

The tropical forms of mollusks alluded to by Dr. Pilsbry
as inhabiting southern Florida are by no means the only ones
that have been collected there. The southern genera
Choanopoma, Truncatella, Microceramus, Cerion and Veroni-
cella (Vaginulus) have also entered this region. One of the
Urocoptidae lived in Florida already in Oligocene times, and
it is quite possible that Microceramus pontificus and M. flori-
danus, which are peculiar to southern Florida, have existed
there ever since. Among many groups of invertebrata long
specific persistence is much more common than is generally
realised. The fact that some of the Floridian species are

* Pilsbry, H. A., “ Origin of Molluscs of South Florida,” p. 193.
+ Dall, W. H., “ Tertiary Fauna of Florida,” Part IV., p. 1565.
t Pilsbry, H. A., “Manual of Conchology (Pulmonata),” Vol. XII,

pp. 109—110.

—
~

CS ee

<p NE Pe

MOLLUSKS OF FLORIDA 177

identical with West Indian ones does not necessarily imply a
recent introduction. Some mollusks, at any rate, seem to have
preserved their specific characters unchanged through several
geological periods. On the other hand, although there cannot
be the slightest doubt that a certain number of species intro-
duced by human agency thrive in other localities besides their
native homes, I am not convinced that mollusks spread across
any wide expanse of sea by other accidental transport. With
Mr. Bryant Walker * I prefer to attribute the tropical land
mollusks of Florida largely to a former land connection
between the then island of Florida and a larger southern land-
mass. I cannot, however, agree with Mr. Walker’s view that
this event took place in comparatively recent times. Dr.
Simpson urges that the Floridian area must have been joined
to the greater Antilles by way of the Bahamas in Eocene
times. Nevertheless, he does not derive the tropical species
of Florida from the southern invasion which must have taken
place at that time. He favours a recent colonisation by acci-
dental transport. The rich fauna, of the Bahama islands seems
to him entirely derived from the greater Antilles in that
manner.}

There are certain geological grounds for the supposition
that an ancient Archaean land-mass trending north-eastward
from the northern end of the Andes once existed, and that
traces of it are still recognisable in Guatemala, Cuba and

~ Haiti.t Much of this early land may still have stood above

sea-level in early, and perhaps middle, Tertiary times, form-
ing a centre from which the North American continent de-
rived part of its present fauna.

Dr. Ortmann § demonstrated in a very convincing manner
that the fresh-water crayfish belonging to the genus Cambarus
originated in Mexico, spreading from this centre of dispersal
into the United States at the beginning of the Tertiary Era.
The centres for the more advanced forms of the sub-genus
Cambarus, and for the sub-genera Faxonius and Bartonius,

* Walker, Bryant, “ Origin of American Mollusca,’’ p. 56.

+ Simpson, C. J., “Land and Freshwater Mollusks of West Indian
Region,”’ pp. 447—448.

{ Frazer, T., “History of Caribbean Islands,” p. 398.

§ Ortmann, A. E., “ Affinities of Cambarus,” pp. 124—125.”

L.A. N

178 ORIGIN OF LIFE IN AMERICA

are situated in the southern States of North America. It is
suggested by Dr. Ortmann that the south-eastern centre of
the early forms of Cambarus originated from the more ancient
south-western one by a process of migration across the present
continent. May not these early forms have travelled eastward
from Mexico towards Cuba and Florida when the latter were
connected directly by land with Central America? A species
of Cambarus still lives in the rivers of Cuba.

Instead of mollusks or crayfish we may take almost any
group of North American invertebrates and readily discover
among them certain ancient forms, which are either confined
to small areas in the south-eastern States or have evidently
spread northward from a south-eastern centre.

Scorpions, for instance, are universally acknowledged to be
a very ancient group. The genus Centrurus has its head-
quarters in the West Indies and Central America. Now
four species of Centrurus are known from Florida, viz., C.
gracilis, C. carolinianus, C. margaritatus and C. hentzi, the
latter being peculiar to Florida. ‘The allied genus Tityus,
which is rather more southern in distribution than Centrurus,
has one endemic species in Florida, viz., T. floridanus.*
Altogether the southern part of Florida shows marked affini-
ties with the West Indies. There are also some species in
Florida such as Cupiennius sallei, Keys, not yet recorded from
the Antilles, which are known from Central America. Quite a
similar southern relationship has been noticed among many of
the Floridian Orthoptera + and the Coleoptera.t One of
the most noteworthy genera of beetles recorded from Florida
is Rhopalomesites. It has spread northward as far as Dela-
ware, and reappears across the Atlantic in western and
southern Europe.

As regards the dragon-flies and their allies (Neuroptera), a
few species are common to the West Indies and the northern
continent. Some of these may have flown, or have been con-
veyed by astorm, from one region to the other. Such a method
of colonisation, however, cannot have been used! by Enallagma,

* Banks, Nathan, “ Arachnida of Florida,” p. 142.
+ Rehn, J. A., and M. Hebard, “ Orthoptera of Florida.”
{ Schwarz, HE. A., “ Coleoptera of Florida.”

ae ee ee ee

SCORPIONS AND DRAGON-FLIES 179

according to Prof. Kolbe,* on account of its feeble development
and weak flight. Taking into consideration the general dis-
tribution of this genus, he favours the view of a former
ancient land connection between the Antilles and North
America.

In its butterflies and moths Florida is united to Central
America and the Antilles, and it is from the latter that such
genera as Heliconius, Dione and Agraulis gained a foothold in
the northern continent.+

An exceedingly ancient group are the woodlice (Isopoda) or
“sowbugs ” as they are sometimes called in America. In
eastern Europe at Odessa, and again in north-western Africa,
an interesting very peculiar species occurs which is known
as Tylos latreilli. The same species has been met with in
southern Florida and in the Bermuda islands. A case of that
kind is generally set down at once as an instance of human
importation. The possibility of the survival of such a species
through several geological ages is not even discussed. But
in southern Florida a second species of Tylos has been dis-
covered which occurs elsewhere only in Bermuda. This
species, known as Tylos niveus, is white in colour and pos-
sesses structural differences distinguishing it from the other.
Of the genus Cubaris, which is widely distributed through the
Antilles and westward to Mexico and California, a single
species (Cubaris pisum) occurs in Florida, and is peculiar
to it. |

All these, it may be objected to, are inconspicuous creatures
that might have been overlooked elsewhere. Too much im-
portance, it might be urged, should not be placed on their
occurrence in Florida. We may return, therefore, to more
conspicuous objects.

Everyone in America knows, or has heard of, the alli-
gator (Alligator mississippiensis), though it is only found
in the southern states of North America. Its distribu-
tion in fact is rather limited. From Florida it extends
northward to Carolina and westward as far as the Rio

* Kolbe, H. J., “‘ Neuroptera der Antillen,”’ pp. 157—158.
+ Pagenstecher, A., “ Verbreitung der Schmetterlinge,” p. 359.
{ Richardson, H., “ Isopods of North America.”

N 2

180 ORIGIN OF LIFE IN AMERICA

Grande. Only one other species of alligator is known, viz.,
Alligator sinensis from the Yangtse River in China.* ‘This
enormously discontinuous range is significant, and implies
great antiquity. Fortunately we possess most valuable
palaeontological evidence as to the alligator’s antecedents.
Even the most pronounced advocate of accidental dispersal
would not venture to apply the usual methods of wind, waves
or hurricanes to explain the origin of this example of dis-
tribution. The generally accepted theory, I believe, is that
some ancestor of the American alligator has travelled north-—
ward, and succeeded in crossing the former land bridge across
Bering Strait to north-eastern Asia, thence wandering south-
ward to China. We possess no fossil evidence for such a
belief. All we know is that the rather generalised alligator
Diplocynodon lived already at the very commencement
of the Tertiary Era both in North America and in Kurope,
and that it persisted in Kurope until Miocene times. Hence
it seems likely that the modern genus Alligator originated in
early Tertiary times either in Europe or North America, and
spread thence to Asia. That America was probably the centre
of dispersal is indicated by certain characters the Chinese
alligator has in common with the South American caimans.
An equally remarkable fact of distribution is that the true
crocodile has succeeded in obtaining a footing on the North
American continent in one single small area, namely, in that
in which I have already signalled so many tropical species,
in southern Florida. We are apt to associate crocodiles with
Africa, Yet they have a much wider distribution. The genus
Crocodilus occurs in Africa, Syria, India and eastward as far
as northern Australia. Westward it reappears in South
America, the West Indies and Central America. The species
alluded to (Crocodilus americanus) is the only member of the
family inhabiting the West Indian islands, and it also occurs
in Central America, Columbia, Ecuador and Venezuela.
Remains of crocodiles found in the Hocene of Wyoming
and the eastern States have been referred by Leidy, Cope
and others to the genus Crocodilus. The presence of croco-
diles in America dates back, then, to the very beginning of
the Tertiary Era, and it seems surprising that they have not

* Barbour, Th., “ Chinese Alligator.”

ee

» i 4eo

HEWN SEE OR ne

failn ees

ALLIGATORS AND CROCODILES 181

spread more widely in America. Although the American’
crocodile is fond of salt marshes, and some of the eastern
crocodiles actually frequent the sea coast, I cannot for a
moment believe in the possibility of a crocodile crossing an
ocean such as the Atlantic. Only a land connection between
America and the Old World in early Tertiary bemies can
explain its present geographical distribution.

Of West Indian mammals none have so far been observed in

Florida, unless we include the raccoons among them. It isa
most remarkable fact that a raccoon (Procyon maynardi)
inhabits New Providence, one of the Bahama islands. At
the first impulse we might think of a chance introduction by
floating trees from the mainland of Florida. But Florida lies
one hundred and seventy miles west of New Providence, and is
separated from it by a swift current flowing northward.
Raccoons occur nowhere else in the West Indian islands,
and the New Providence species differs from that of the main-
land. In the last chapter (p. 151) I contended that the
whole family Procyonidae was certainly of American origin,
and I thought the genus Procyon might have arisen in Plio-
cene times. Possibly it is much older, though we possess no
palaeontological evidence in support of such a supposition. If
the Bahama islands had still been joined to Florida when the
latter had already become a peninsula of North America, we
should expect a good many of the smaller mammals to have
crossed over to the Bahamas, which they have not done. So
far, the occurrence of this species of raccoon in the Bahamas
is a complete puzzle to me.
- Before concluding this brief survey of the south-eastern
fauna I should like to dispel the impression I may have given
that the tropical element forms any great share in the verte-
brate fauna of Florida. On the contrary, the majority of the
genera and species undoubtedly poured into the peninsula
from the north and north-west, and they appear to be gradu-
ally displacing the southern element. Atany rate, 1 look upon
the latter as a relict of the Tertiary Era.

There are many species of mammals peculiar to Florida,
but not so many as we might expect from the favourable
climatic conditions of the country. On the whole, the
mammalian fauna of the peninsula bears the impress of a

182 ORIGIN OF LIFE IN AMERICA

newly emerged land which has been populated from the north
within recent geological times. The most noteworthy species
that might be mentioned is the Florida water vole (Microtus
alleni). It is not alone the only North American water vole,
but also the sole member of the sub-genus Neofiber, and thus
forms a connecting link between the genera Microtus and
Fiber, that is to say, between the meadow voles and the
musk rats.*

I have endeavoured to describe in almost every chapter the
range of some typically ‘North American mammal. Some have
not yet been alluded to, among them the opossum. ‘Two
species are now often distinguished in North America,} one of
which is supposed to extend its range into South America. As
a matter of fact the northern and southern forms are
extremely difficult to discriminate from one another, and
many authorities are of opinion that they merely represent
varieties of one species (Didelphys marsupialis) which thus
has an enormously extensive distribution in North and South
America.

The existing marsupials, or pouched animals as we may call
them, are generally regarded as modern survivors of one of the
ancient groups of mammals, which apparently spread almost
all over the globe before the superior beasts of more recent
times had made their appearance. It is believed that at the
time of their prime, Australia became separated from the
mainland of Asia, so that this southern continent now forms
the headquarters of the group, while in other parts of the
world they succumbed in the struggle with superior and better
fitted animals. Yet in America, where competition with the
more highly developed and more aggressive beasts ought to
be very keen, opossums, which belong to the marsupials,
are by no means on the verge of extinction. On the

contrary, they hold their own perfectly against the more —

modern competitors. The genus Didelphys is much more
abundantly represented in South America than on the
northern continent, and other genera of marsupials occur

there besides opossums. ‘To judge from these modern repre-

* Bangs, Outram, “ Mammals of Florida and Coast Region.”
+ Allen, J. A., “ North American Opossums.”’

!
:
7
4
‘

THE ISLAND OF BERMUDA 183

sentatives of the marsupials, it would not be unreasonable to
argue that the opossums had invaded North America from the
southern continent. Mr. Lydekker’s * conclusion is that
opossums are only recent immigrants from the south,
although he does not believe that South America was their
original home. He (p. 55) selects south-eastern Asia as the
birthplace of the opossum family (Didelphyidae), urging that
the latter scattered from this centre towards Kurope and North
America. He also contends that the allied family Dasyu-
ridae originated in southern Asia, spreading thence to
- Australia, and by an antarctic land connection from there to
South America. I shall return to this subject in some of the
subsequent chapters (p. 283 and p. 866).

_ There is still another problem of exceptional interest which
I wish to enlarge upon, namely, that of the origin of the
Bermudan fauna. The island of Bermuda has certain
faunistic affinities with Florida, and we may therefore con-
sider the origin of its fauna as an appendix to this chapter.
It consists in reality of a series of about one hundred
islands and islets, their total area being less than twenty
square miles. The island of Bermuda, as we may call it for
the sake of brevity, lies approximately seven hundred miles
eastward of North Carolina, being apparently surrounded on
all sides by a depth of from 1,500 to 2,000 fathoms.
Dr. Wallace,f who gives us a brief description of the
fauna and flora of the island, concludes that Bermuda
furnishes us with one of the most instructive facts as to the
power of many groups of organisms to pass over seven
hundred miles of open sea. There is no doubt whatever,
he remarks, that all the indigenous species have thus reached
the island. ,

I may as well say that my own views differ entirely from
those of Dr. Wallace as regards the origin of Bermuda and of
its indigenous fauna and flora. I believe the island to have
formed part of a wide belt of land, which extended northward
from the West Indies, joining the mainland of North America
somewhere near Massachusetts, at a time when most of the

* Lydekker, R., “ Geographical History of Mammals,”’ p. 108,
t Wallace, A. R., “Island Life,” p. 273.

|

|

eae eS

184 ORIGIN OF LIFE IN AMERICA

existing coast line of the Atlantic States south of Massachu-
setts was submerged (Fig. 14). I look upon the indigenous
animals and plants of Bermuda as relicts of an ancient fauna
and flora. I hold, moreover, that Bermuda furnishes us with
one of the most instructive facts of the exceedingly slow
change that many species of animals and plants undergo
through successive geological ages, and that it does not sup-
port the theory advocated by Dr. Wallace that many organisms
possess the power of crossing seven hundred miles of open
sea.

The geology of Bermuda, so far as the visible structure is
concerned, is identical with that of the Bahamas, except that
the coral reefs are of greater importance in the latter. The
rocks in both are limestone, and red clays resulting from its
decomposition. Nearly all the rocks of Bermuda above
sea-level, and to a considerable depth below it, are made up of
wind-drifted shell sand with very little material derived from
corals and other organisms. These materials, according to
Professor Verrill, when consolidated, form a true aeolian lime-
stone. The island is surrounded by coral reefs in such a
manner as to give it the appearance of an atoll of the Pacific
Ocean. It was actually regarded as such by Professor Rice.*

The greater Bermuda or ‘“ Pliocene Bermuda ”’ as it has
been called, which was once dry land, had an area of about two
hundred and thirty square miles. That this greater Bermuda
represents an older land surface was revealed during the exca-

> vations made in 1870 for harbour works. These extended to

over fifty feet below sea-water level. At a depth of forty-
six feet, as Mr. Jones 7 tells us, a stratum of peat and red
earth two feet thick was found, containing the vertical stumps
of cedar trees. This again rested on hard aeolian limestone,
containing fossil land shells of the genus Poecilozonites.
There is clear evidence, therefore, of a subsidence of the
land to the extent of at least fifty feet. A re-elevation to
that extent would nearly restore the island of greater
Bermuda. Beyond this, in a south-westward direction, several
shallows have been detected, all being surrounded by great

* Tice, W. N., “ Geology of Bermuda,’’ p. 9.
+ Jones, J. M., “ Recent Observations in Bermudas,”’ p. 262.

GEOLOGY OF BERMUDA 185

depths, yet indicating that they represent a range of drowned L
mountains. |
According to Professor Verrill it is now generally admitted
that Bermuda is the flattened and greatly eroded summit of a
vast submarine voleano, and he thinks it most reasonable to
suppose that its last activity corresponded in time with the
last great volcanic eruptions of the nearest American main-
land. This, as he remarks, would imply that the Bermuda
voleano was formed or completed during the Triassic Period
or at its close. Immense outbursts of volcanic material took
place all along the eastern coast of America at that time,
giving rise to enormous trap-dykes. In Nova Scotia these
dykes have a nearly north and south direction, and they may
have had some direct relation with the voleano of Bermuda.
It is estimated that the latter had a height of about 15,000 feet.*
The whole surface structure of Bermuda reminds us vividly
of the Bahamas. The latter owe their configuration to the
same process of waste which has been going on during their
subsidence. The coral reefs surrounding the Bahamas form
but an insignificant part of the topography of the islands.
_ ‘The same aeolian rocks as in Bermuda cover all the visible
parts of the Bahamas, and we find an intercalation of similar
_ red earth. Altogether there is, as Professor Agassiz points
out, clear evidence of the comparatively recent subsidence
of at least three hundred feet of the Bahama Bank.t
A slightly greater elevation would have had the effect of
shutting out the Gulf Stream from the northern Atlantic,
for it now pursues its swift northern course through the
shallow channel lying between the Bahama Bank and Florida.
Now it is interesting to note that the ancestral Gulf Stream
|

did not flow where it does now, but across northern Florida,
thus separating the northern from the southern portion of the
peninsula. Not only were northern Florida and Georgia sub-
merged. Tertiary marine deposits are known even as far north
as New Jersey. The sea covered a vast area of the present
southern Atlantic States. That a strong current flowed
through the channel of north Florida is evidenced by the fact

* Verrill, A. E., “ Bermuda Islands—Geology,’’ XII., pp. 47—82.
+ Agassiz, A., ‘‘ Reconnaissance of Bahamas,” p. 7.

186 ORIGIN OF LIFE IN AMERICA

that during early Tertiary times Antillean species were carried
even as far as New Jersey. At no succeeding Epoch, says Dr.
Dall, do we find such tropical and semi-tropical mollusks
extending northward to such a distance from their present
range. All these Tertiary deposits cease north of the Hudson
estuary, and I have shown in a previous chapter (p. 41)
that in later Tertiary times, at any rate, the coasts of New
York, Massachusetts and Maine extended far out into the
present Atlantic. The hypothesis of the latter land extension
having once joined Bermuda and the Bahamas, etc., seems to
me supported by a variety of circumstances which I shall
allude to later on. This would have excluded the Atlantic
Ocean either partially or wholly from the Gulf of Mexico and
the southern Atlantic States. Some time during the Miocene
Period, or earlier, a sudden influx of northern species into the
area hitherto occupied by southern forms occurred. Dr. Dall
and Mr. Harris * endeavoured to account for this phenomenon
by the supposition that the course of the Gulf Stream was
gradually turned more off shore than it was before or is at
present.

If we assume, however, that a belt of land such as above
described had hitherto existed, the gradual breaking down of
its northern portion might have admitted the Atlantic waters
into the sea which covered the southern States and have
brought with it the new fauna, which had meanwhile deve-
loped in the northern Atlantic Ocean (see Figs. 14 and 16).
For a time these northern, cooler inshore waters were even
able to penetrate into the Gulf of Mexico. Even if we grant
the correctness of Messrs. Dall and Harris’s supposition of the
altered course of the Gulf Stream, the cause of this deflection
is more likely to have been produced by a change in the con-
figuration of the northern land-masses than by that of Florida.

Let us now study the flora and fauna of Bermuda, and _
endeavour to ascertain whether it supports in any way the
theory IL have advocated.+ It is quite evident that the existing
flora of Bermuda is only a remnant of the original one, before
the early settlers, accompanied by hogs and rats, played havoc

* Dall, W. H., and G. D. Harris, “ Correlation Papers,’’? pp. 185—187.
+ Heilprin, A., “ ‘The Bermuda Islands.”’

FLORA OF BERMUDA 187

with it. The old records speak of thousands of palmetto trees
that were cut down, and of cedars used for the construction
of ships and buildings. The palmetto (Sabal blackburniana)
is a species of palm much like that of southern Florida, but
differing sufficiently to form a distinct species. All the islands
were once thickly covered with the cedar (Juniperus bermu-
diana), and it also occurs in a semi-fossil condition in the
red earth. Among the one hundred and fifty six kinds of land
plants now considered native to Bermuda, about fifty species
are very restricted in their distribution, most of them being of
West Indian origin. Altogether one hundred and eighteen
species are native of the West Indies. Of these ninety are
also found in Florida, the remainder being only met with in
the West Indies. About the same number of plants as are
common to Bermuda and the West Indies only, are also
peculiar to Bermuda and continental North America. A few,
such as the blue-eyed grass (Sisyrinchium bermudianum),
have their nearest relatives in the north-eastern States. Most
of the botanists who have investigated the Bermuda flora,
especially Mr. Hemsley, Mr. Moseley and more recently Pro-
fessor 8. Brown, Dr. Harshberger and Professor Verrill * are
agreed that all the native plants of the island have been: intro-
duced by natural agencies prior to the advent of man. Pro-
fessor Verrill is of opinion, and I feel sure his view is
almost generally accepted, that migratory birds have prob-
ably always been the chief agencies for these introductions
of plants, especially those from north-eastern North America.
Currents, floating timber and hurricanes are also supposed
to have had their share in transporting plants from various
parts of America to Bermuda.. [am among tthe few who do not
recognise the potency of these agencies of transport. That
seeds are occasionally cast by currents upon the shores of
lonely islands like Bermuda has been amply proved, but there
is no evidence available to show that migratory birds distribute
seeds on siuch islands, or that hurricanes carry seeds across
seven hundred miles of sea and safely deposit them on an
island. These theories are very widely accepted, but I think
on insufficient grounds.

* Verrill, A. E., ‘‘ Bermuda Islands,” XI., pp. 587—é88.

188 ORIGIN OF LIFE IN AMERICA

Dr. Wallace * makes the statement that the few species of
birds which are resident in Bermuda and breed on the island
are so constantly crossed by individual migrants of the same
species from the mainland that none of the former have
acquired any special peculiarity constituting even a distinct
variety. It is perfectly true that the resident land birds
are very few in number, but the opinions of most recent autho-
rities differ very considerably from those enunciated by Dr.
Wallace.

Only ten species of land birds are resident on the island,
and three of these have been introduced by man. The indi-
genous fauna includes, therefore, seven kinds of birds,
namely, the ground dove, the Florida gallinule, the crow, the
white-eyed Vireo, the blue bird, the cat bird and the cardinal.

Of these the Bermuda ground dove (Columbigallina bermu-
diana) is described as a species very distinet from the
American C. passerina. ‘The Florida gallinule (Gallinula
galeata) does not seem to differ from the continental form.
The crow of Bermuda is probably separable from the American
crow, but has not been sufficiently studied. The white-eyed
Vireo (Vireo bermudianus) is described by Messrs. Bangs
and Bradlee as very different in all its ways from its shy,
retiring, continental relative, V. noveboracensis.+ The blue
bird is not usually recognised as distinct from the continental
form, but Dr. Sharpe of the British Museum held that ‘its
characters were certainly striking enough to deserve specific
recognition, and he described it as Sialis bermudianus. Now I
may mention that the blue bird belongs to one of those genera
which seem to have retained their generic characters for very
long ages past, probably throughout several geological periods.
We know nothing of its past history from palaeontological evi-
dence, but its present geographical distribution, and that of
its nearest relative, are so peculiar as to suggest their being of
great antiquity. Sialis, with its three closely-allied American
species, has its nearest relative (Grandala) in the Himalayan
Mountains. I only mention this fact so as to show that the
apparent specific identity of the Bermudan and the continental

* Wallace, A. R., ‘‘ Island Life,” p. 269.
t Bangs, O., and T. S. Bradlee, “‘ Birds of Bermuda,” pp. 249—257.

BIRDS OF BERMUDA 189

blue bird need not necessarily be adduced as an argument
for the recent geological origin of the former. The Bermuda
catbird (Galeoscoptes bermudianus), though closely resem-
bling the continental species, is considered distinct by Messrs.
Bangs and Bradlee and by Dr. Sharpe. Finally, the Bermuda
cardinal (Cardinalis bermudianus) can at once be identified
from its continental relative by its characteristic bill.

Dr. Wallace alludes to the Bermudan lizard as being the
only vertebrate animal which exhibits any peculiarity. But
much more can be said about it. It is a member of the family
of skinks (Scincidae), which is of cosmopolitan range and
undoubtedly of great age. The Bermudan skink (Humeces
longirostris) is said to be nearly related to the American blue-
tailed lizard (Kumeces quinquelineatus), still we must remem-
ber that the latter has long been considered identical with the
Japanese skink (Eumeces latiscutatus) from which it can
be separated only by very careful study.* It may safely be
argued, therefore, that the Bermudan skink has originated in
early Tertiary times (compare pp. 123—126).

Dr. Rehn + records twenty-eight species of Orthoptera, two
of them, viz., Paroxya bermudensis and Gryllus bermudensis,
being peculiar to the island. If we exclude the cosmopolitan
and circumtropical forms which the author regards as prob-
ably introduced by commerce, the remainder are more closely
related to continental than to Antillean species.

Only a single ant is peculiar to Bermuda, viz., Prenolepis
kincaidi, because some of the more active recently introduced
warlike species have no doubt exterminated the greater part
of the older resident ant fauna. {

Mr. Pocock § recognised two species of myriopods from
Bermuda as doubtfully distinct, though he described them as
new species. These are Lithobius provocator and Lithobius
bermudensis. Altogether he believes that only six species
of centipedes and millipedes are native to Bermuda, and that
three of them belong unquestionably to the Mediterranean

* Garman, Sam, “ Reptiles of Bermuda,” p. 287.

+ Rehn, J. A. G., ‘‘ Orthoptera of Bermuda,” p. 3.

t Wheeler, W. M., ‘‘ Ants of Bermuda,” p. 347.

§ Pocock, R. I., ‘‘ Myriopoda of the Challenger Expedition,” pp. 128—
124.

190 ORIGIN OF LIFE IN AMERICA

fauna. This is a point of considerable interest and import-
ance, and requires to be more closely studied in a recon-
sideration of the true relationship of the members of other
groups of invertebrates.

This relationship is clearly recognisable among the ter-
restrial Isopods or wood-lice, which have been described
by Miss Richardson. Tylos latreilli, as already quoted,
is a typical Mediterranean species, which has been dis-
covered in southern Florida, where also another species,
Tylos niveus, occurs. Both of these are now recorded from
Bermuda. The European genus Porcellio is represented by
two species, one of them (Porcellio parvicornis) new to
science. Metoponorthus sexfasciatus, a typically Mediter-
ranean species, also found in the Canaries and Azores, occurs
in Bermuda, but nowhere else in America. Another species
peculiar to Bermuda (Philoscia bermudensis) is closely
related to the west European Philoscia couchi. The
American affinities are likewise surprisingly interesting.
Uropodias seems to be related to the West Indian genera
Haplarmadillo and Sphaeroniscus, and this strikingly distinct
genus is quite confined to Bermuda with the one species, Uro-
podias bermudensis. The truly archaic Actoniscus ellipticus,
which is only known from Bermuda and from the coast of the
mainland near New Haven and Long Island Sound, is one
of the only two members of the family Trichoniscidae. Its
distribution is suggestive of a former land connection towards
north-eastern North America. The other Actoniscus is con- —
fined to California. Finally, Leptotrichus granulatus, also
peculiar to Bermuda, may be mentioned as the only occurrence
of a very ancient Old World genus in America.*

The only native spider which, according to Dr. Verrill,+ was
mentioned by the early writers, was the great silk spider
(Nephila clavipes). The enormous webs which this spider —
constructs between trees at a distance of fifty feet from one
to another excited their admiration, and suggested to them
that the threads might be used in the manufacture of silk
tissues. This has actually been done in Brazil, I believe,

* Richardson, Harriet, ‘‘ Isopods of Bermuda.”
+ Verrill, A. E., ‘‘ Bermuda Islands,”’: XI., p. 829.

WOOD-LICE AND SPIDERS 191

where this spider occurs. The silk spider is known from
Brazil, from Central America as far north as Texas, and from
Southern Florida. Professor Dahl* argues that the group to
which this species belongs already had a wide range in Cre-
taceous times. Its nearest relation, Nephila clavata, is pecu-
liar to China and Japan. It is quite possible, therefore, that
the American form may have existed since early Tertiary
times. But, as Dr. Marx + observes, the spiders introduced by
human agency have not only acclimatised themselves; they
have also, in a more or less marked degree, driven away and
exterminated the indigenous spider fauna. Yet among the
remnants of that ancient fauna we recognise four species that
are peculiar to Bermuda. Most of the remainder are identical
with American forms.

One of the most noteworthy animals that might be adduced
in favour of the theory that Bermuda represents the remnant —
of a large land surface once connected with the mainland is
the land nemertean Geonemertes agricola. This very pecu-
liar worm is found in abundance at several distinct localities
in Bermuda. It might be said that this worm is not of much
zoogeographical value, since it is able to resist immersion in
sea-water for some time. On the other hand, it must. be re-
membered that land nemerteans have an extremely discon-
tinuous range on ancient land surfaces. Hence their distribu-
tion is suggestive of great antiquity. Nine species of the
genus Geonemertes are now known from Australia, New Zea-
land, New Guinea, Pelew Islands, Rodriguez Island, the
Seychelles and Bermuda. ‘To suggest that Geonemertes
agricola owes its presence in Bermuda to an accidental intro-
duction would be quite inadmissible, because it has never
been found elsewhere.{

Of greater importance than any of the foregoing inverte-
brates are the land and fresh-water snails inhabiting
Bermuda. Dr. Pilsbry distinguishes autochthonous species,
drift waifs from the West Indies, and snails imported by the
agency of man. ‘The last group we need not consider here,

* Dahl, F., ‘ Verbreitung d. Spinnen,”’ p. 278.
t+ Marx, G., ‘‘ Spiders of Bermuda,” p. 100.
t Coe, W. R., ‘* Geonemertes agricola,” p. 534.

>.

192 ORIGIN OF LIFE IN AMERICA

although some members of it are probably indigenous. The
remainder include several snails, only once recorded, and
not again found on the island in recent times. he
so-called waifs from the West Indies are of greater signific-
ance. Dr. Pilsbry identifies Succinea bermudensis with
S. barbadensis, yet acknowledges that the shells of this
genus are peculiarly uncharacteristic, and that species of
different regions frequently resemble each other. All con-
chologists, however, are agreed that the semi-amphibious
amber-snail (Succinea), with its almost world-wide distribu-
tion, must be a very ancient one. The mere fact of several
Bermudan species being identical with West Indian ones
is no proof that they were conveyed to Bermuda by accidental
means of transport. I have argued this point again and again,
but it is a widespread assumption which can only be effectu-
ally disproved by palaeontological evidence. No such evidence
is available in the majority of cases. Yet of someof these sup-
posed accidentally and recently introduced species of Bermuda
I might mention Rumina decollata. It is certainly native in
the Mediterranean region, where it exists,as a relict ofthe, past,
and I have given a map of its range in my work on European
animals.* The family Stenogyridae, to which it belongs, is
an entirely tropical one. Rumina decollata has adapted itself
to the HKuropean climate, though its shape has remained un-
changed since Oligocene times. It has been known to exist
outside Europe in Cuba, South Carolina and Bermuda. Are
we justified in the assumption that this exceedingly old
member of a tropical family of snails has been accidentally
introduced into these localities? I think not, and yet this
surmise is received by almost everybody as an established
fact.

The really interesting members of the Bermudan fauna of
mollusks are those styled “autochthonous ’”’ by Dr. Pilsbry,
viz., Helicina convexa, Thysanophora hypolepta, all the
species of Poecilozonites, and the slug Veronicella schivelyae.

I have already dwelt upon the distribution of the genus
Helicina (p. 158), and on its occurrence in the Oligocene
Silex beds of Tampa in Florida, and have indicated that it

* Scharff, R. F., ‘‘ Huropean Animals,”’ p. 222.

ee eee

SNAILS OF BERMUDA 193

represents a relict of early Tertiary times. The ancestors of
Helicina convexa, which is peculiar to Bermuda, reached the
island presumably in the Oligocene Period, when we know
that the genus inhabited the island of Florida.

Thysanophora is a member of the large family of Helicidae.
It is most characteristic of the West Indian region and Central
America, and Dr. Pilsbry * declares that it represents the
oldest stock of the West Indian Helix fauna. The ancestors
of Thysanophora hypolepta may well have wandered to the
Bermudan area from the West Indian region in early Tertiary,
times. This suggestion is strengthened by the fact that along
with Succinea and Poecilozonites it is found fossil in the
“red earth.” The genus Poecilozonites, with its four
Bermudan species, is peculiar to Bermuda. Recently Pro-
fessor Boetiger + again drew attention to the intimate rela-
tionship existing between this genus and the German lower
Miocene Helix imbricata, in spite of Dr. Pilsbry’s plea that
the German savant was only chasing an “ ignis fatuus.” Dr.
Pilsbry { prefers to derive Poecilozonites from an old
American stock, arguing that it is related to Gastrodonta. To
trace the exact affinity of a recent to a fossil form is always
a matter of considerable difficulty, but since several: other
Huropean palaeontologists have dwelt upon the remarkable
and undoubted relationship existing between the present West
Indian fauna and the fauna of the European early Tertiary
deposits, and as I shall be able to bring forward additional
evidence in favour of their views, I am certainly on Professor
Boettger’s side in this controversy. That Poecilozonites is
not a recent arrival from elsewhere, quite apart from the fact
that it is unknown outside the Bermudan area, is likewise
indicated by its fossil occurrence in the red earth, which
is held to be of Miocene or Pliocene age. Dr. Gulick § records
eleven species and sub-species of Poecilozonites from the red
earth, as well as Succinea bermudensis and a number of
genera that have since become extinct.

* Pilsbry, H. A., ‘‘ Manual of Conchology,” Vol. IX., p. 56.
+ Boettger, O., ‘‘ Helix-Arten aus d. Tertiir Europas,” p, 103,
{ Pilsbry, H. A., ‘‘Mollusks of Bermuda,” pp. 491—609.
§ Gulick, A., “ Fossil Land Shells of Bermuda.”

L.A. 0

194 ORIGIN OF LIFE IN AMERICA

Mr. Vanatta * recently made the interesting discovery that
several typical fresh-water species inhabit Bermuda. Among
them there is a Physa, two Planorbis, one Ancylus, a Palu-
destrina and a Pisidium. All are new to science.

The genus Veronicella (Vaginula), of which a species (V.
schivelyae) inhabits Bermuda, includes slug-like creatures
which should certainly not be suitable for accidental dispersal
by the usually quoted agencies. It is of interest, therefore, to
note that Messrs. Robbins and Cockerell + record a variety of
the Bermudan Veronicella from the Bahama islands, and
direct attention to its close relationship with the Mexican
Veronicella moreleti.

From the foregoing brief survey of the Bermudan fauna it
is manifest that although that most destructive of all creatures
““man,” has played havoc with the native animals and plants,
largely exterminating them, a recognisable residue has sur-
vived from remote times. ‘As far as the ancestry of this relict
fauna can be traced, it seems to be derived from the south-
eastern and north-eastern States of America, from the West
Indies and even from southern Europe. Many species, par-
ticularly such as are unfit to take advantage of accidental
modes of transport, namely, the Bermudan skink, the
terrestrial nemertean worm, and various kinds of terrestrial
isopods and snails, are peculiar to Bermuda. Is there any
reason for the supposition that these animals, all of which
bear the impress of vast antiquity on them, were conveyed
to Bermuda in the past by accidental means ? We have no evi-
dence whatever that terrestrial invertebrates are transported
alive across seven hundred miles of sea and subsequently pro-
pagate their kind except through the agency of man. Why
should we assume, therefore, that Bermuda has received its
entire fauna and flora by accidental means such as winds,
hurricanes or ocean currents? It is evident that the great
depths of the ocean surrounding the little group of islands is
the chief, if not the sole, stumbling block to the acceptance
of the survival theory. Yet in view of the fact vouched for by

* Vanatta, E. G., ‘“‘ Bermuda Shells,” pp. 668—672.
+ Robbins, W. W., and T. D. A. Cockerell, ‘‘ Veronicella,” p. 383-—

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ORIGIN OF BERMUDA 195

Professor Suess, that a subsidence of land amounting to
10,000 feet has taken place between the island of Rhodes and
the mainland of Syria in post-Pliocene times, whereas marine
deposits of late Pliocene age occur in the southern Andes at
a height of 5,000 feet, is it really such an unlikely theory that
the supposed ancient belt of land connecting Bermuda with
a southern land-mass has subsided to a similar extent within
comparatively recent geological times ? I need not dwell any
longer on this problem. When I come to deal with the
Antilles and the origin of their fauna further allusions to it
will be made. !

0 2

CHAPTER IX

SOUTH-WESTERN NORTH AMERICA

THE region to be dealt with in this chapter is of enormous
extent. To speak of it vaguely as south-western North
America is apt to give the impression as if only Texas
and the adjoining western States were being considered.
What is described here under that designation contains almost
the whole of the western States with Mexico in addition.
There is material enough for several chapters. Nevertheless,
the profound zoogeographical importance of this portion of
North America will be more readily realized, I think, if the
leading facts are compressed into one brief essay. The Rocky
Mountain fauna, moreover, which enters largely into the
south-western region, has already formed the substance of a
special chapter.

The term “ Sonoran Region” was first applied by Pro-
fessor Cope to part of this important south-western life area,
because he recognised the striking difference it presented as
compared with other parts of the United States. In one of the
previous chapters I alluded to the scarcity of lizards in the
eastern States in comparison with western Hurope. I might
have said “‘ western States of North America” instead of
western Europe, for lizards especially, and reptile life in
general, abound in the region we are now considering.

The term ‘‘ Sonoran,’’* derived from Sonora, a province of
northern Mexico, is now often applied to the fauna of the
whole of North America except the boreal portion; and Pro-
fessor Carpenter + supports the contention that the continent
can be readily divided into two faunistic sections, one of which
is distinctly autochthonous, the other derived from northern
Europe and Asia. I have already put forward my reasons for

* Merriam, ©. H., “ Distribution of Life in North America,” p. 26.
+ Carpenter, G. H., “ Nearctic or Sonoran ?”’ pp. 53—-57.

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SONORAN REGION 197

abandoning faunistic regions in a work of this kind, and I
feel there is little advantage in discussing the merits of one
regional system above another. I only wish to direct attention
to the fact that the distinctness and importance of this south-
western part of North America had long ago been recognised
by zoologists. Professor Carpenter urges that two distinct
faunas exist in America. I can trace even more than two,
for a South American element is very prominently diffused
throughout a large portion of the States. I cannot concur
at all in Dr. Merriam’s view* that ‘“‘except for the
presence, chiefly in the southern United States, of a compara-
tively few forms derived from the tropical region, the fauna
and flora of North America are as distinctive and indepen-
dent of the existence of this area as if separated from it by
the broad ocean.” ‘To place ourselves within fixed and
strictly limited boundaries at all seems to me a mistake. I
do not limit myself in any way to political frontiers, and
if I had set myself a boundary, I should have been inclined to
place it across the isthmus of Tehuantepec. At this point
North America was evidently separated for some time from
Central America by a marine channel, though this division
was not so effectual in keeping two great faunas distinct as
one might expect. All this, however, will be discussed at
greater length when we come to deal with the fauna of Central
America.

Although vast tracts of south-western North America are
nothing more than deserts, there is, on the whole, an extra-

ordinary abundance and variety of animal life. I have

repeatedly pointed out in previous chapters that the roots
of certain groups of eastern animals must be looked for in
the south-west or west. In drawing attention to the strange
affinities of some apparently very ancient east-American
forms, such as the smooth and the rough green snakes, and
east-Asiatic snakes, I urged that they must originally have
spread eastward from south-western North America (p. 125).
Among the tortoises, too, certain eastern groups can be
traced to a remote western origin, although no longer,
resident there. Thus there has arisen a comparatively modern
repetition of that dissimilarity between the eastern and

* Merriam, O. H., “ Distribution of Life in North America,” p. 37.

198 ORIGIN OF LIFE IN AMERICA

western faunas which was the characteristic feature of the
two ancient land-masses during Mesozoic times when the
latter were separated from one another by a wide ocean.
Dr. Pilsbry * once advocated the view, from a conchological
standpoint, that the Sierra Nevada divided North America
into two primary faunal provinces, a division which he thought
commenced in Jurassic times with the upheaval of this moun-
tain range, the latter having proved insurmountable to most
land snails. The true autochthonous American fauna east
of the Sierra Nevada range seemed to him to have developed,
with very little or no trace of Old World influence, from an
early period, probably the Cretaceous.

This difference between the east and west is in many
respects less pronounced when we include Mexico in our
western district. Few species of the characteristically
eastern snail Polygyra are found in California. Further
south, however, in Mexico, their numbers again increase. The
family of perches(Percidae) are quite absent from the western
States. In Mexico they again appear. Among the garpikes
(Lepidosteus) and the Unionidae we notice a similar distribu-
tion, but it is not discontinuous. Their range passes gradu-
ally from the Gulf States into Mexico. Among other groups
or genera a greater discontinuity of distribution is noticeable
between the Mexican and the east American centres of dis-
persal. The tribes that are affected by desert conditions,
and many of them are, would find the arid regions lying
directly to the north of Mexico effectual barriers to dispersal
in that direction. But we have good reasons for the belief that
these desert conditions are comparatively modern develop-
ments, and have little to do with the origin of the distribution,
referred to. The geological history of the south-western
States may throw further light on this problem.

From Cambrian to Jurassic times the greater part of Cali-
fornia was raised above sea-level. Towards the end of the
Mesozoic Kra there existed in western North America a
broad strip of land running north and south being bounded
on each side by the sea.t Mexico must have extended further

* Pilsbry, H. A., “ Check-list of Land Shells,”’ pp. 194—195.
t+ Schuchert, Charles, ‘‘ Paleogeography of North America.”

CALIFORNIAN PALAEOGEOGRAPHY 199

west at that time, since no late Mesozoic deposits are known
from the western parts of that country. If we supposed that
western Mexico had then been connected with some other
land surface, a faunistic interchange could have taken place
_ between the latter and western North America.

In early Tertiary times the central sea, which formed the
eastern boundary of the western belt of land referred to, had
almost disappeared from the interior of America, but large
tracts of western California were still under water (see
Fig. 14). Professor Smith * argues that a temporary con-
nection must have existed during the Eocene Period between
the Atlantic and the Pacific Ocean, because the cha-
racteristic Atlantic shell Venericardia planicosta had been
met with in the Eocene deposits of California and Oregon.
In Oligocene and Miocene times the whole of the eastern
borders of Mexico were submerged, while the sea was at
first retreating from western California and then again
invading it. During the latter part of the Miocene Period
the sea even encroached on western Mexico.+ All the
same, certain parts of the coast ranges in western Cali-
fornia never seem’ to have been entirely submerged during
Tertiary times and probably formed part of the Pacific land
belt which has now almost entirely vanished. I think
the alternative union and disruption of these western Cali-
fornian land-masses with the mainland of North America
must have played an important role in the origin and
development of the American fauna. It seems as if Mexico
had at first formed the stepping-stone to North America for
new immigrants, and later on western California. I have
endeavoured to represent this idea on two maps (Figs. 14 and
16), but how the changes were actually brought about has not
been made quite clear to us through geological research.

It has been suggested by Messrs. Ordonez and Aguilera that
the Cape portion of lower California really forms the western
continuation of the Mexican Sierra del Sur.{ But the very
important question now arises from a zoogeographical point

* Smith, Perrin, “ Geological History of California,’ pp. 347—348.
Tt Arnold, Ralph, ‘Tertiary Pectens of California.”
t Suess, E., “ Antlitz d. Erde,”’ ITT?, p. 487.

200 ORIGIN OF LIFE IN] AMERICA

of view, how far westward and southward of the Gulf of Cali-
fornia did this land extend? No Cretaceous or Tertiary
deposits have yet been discovered on the greater portion of
the Pacific coast of Central America. Geological evidence is,
therefore, rather in favour of the supposition that this western
land formerly extended further south.

As regards the present arid semi-desert conditions of
Arizona and New Mexico, they supported in early Tertiary
times, as I have already mentioned, a wealth of animal
life. In the neighbouring state of Colorado the wonderfully
preserved impressions of insects in the volcanic tuffs of
Florissant, which have been described by Dr. Scudder and
more recently by Professor Cockerell,* leave no doubt as to the
former climatic conditions of that part of America and its
suitability for plant and animal life. The vast outpouring
of lava and general volcanic disturbance in the Rocky Moun-
tain region continued through Miocene and partly through
Pliocene times. All the same, the immigration of tropical
types of mammals from South America into the Western
States at that time would seem to imply the existence in the
latter of a luxuriant flora. Even in Pleistocene times an
abundance of large mammals, such as elephants and masto-
dons, existed in southern California, and probably in the
neighbouring States, to judge from the number of sabre-
tooth tiger remains recently discovered in the asphaltum
beds of Rancho la Brea near Los Angeles. The gradual
desiccation noticeable in some of the south-western States
is obviously a recent development, though the abundance
and diversity of cactuses and of reptiles adapted to a desert
life imply that local arid areas must have existed for long
ages past.

If the geological history of the extreme south-west of North
America has been correctly interpretated in this very brief
summary, we should certainly find relicts of ancient animal
and vegetable types in some of the western areas that have
remained unsubmerged during Tertiary times. For although
most animals would tend to spread from these old centres as
new land became available for their dispersal, some of the

* Cockerell, T. D. A., “ Fossil Fauna and Flora of Florissant.”

SOUTH-WESTERN INSECTIVORES 201

less active and less vigorous types must have remained in their
ancient western habitats.

Among the order Insectivora which is now on its way
towards extinction, several peculiar mammals, such as
Atophyrax, Notiosorex and Scapanus are entirely western
in range. The most noteworthy is what has been called the
mole-shrew (Neiirotrichus), on account of its shrew-like look
combined with its digging habits. The single species Netro-
trichus gibbsi is a western rather than a south-western
animal, being confined to northern California and Washington
State. It has no near relations in America. Its nearest akin
inhabit eastern Asia and Europe, but it has not yet been
satisfactorily established to which of its two Old World
‘branches it has most affinity. The whole group to which all
these insectivores belong is known from the European
Eocene onward. Nowhere else have fossils been found.
Palaeontological evidence would, therefore, point to Hurope
as the centre of evolution. Possibly the ancestors of Neitiro-
trichus may have originated somewhere in the Mediter-
ranean region, have crossed the Atlantic by a mid-Atlantic
land bridge to California, as I shall explain later on, and have —
then passed to Japan, where a closely related genus occurs.

The mole-mice (Onychomys), which are typical rodents,
constitute a section which has evidently originated in the
south-west, and has since spread northward and eastward so
as almost to reach the Mississippi, though none of them have
crossed this river. The wood-rats, belonging to the genera
Nelsonia, Xenomys, Neotomodon, Teanopus and Hodomys
are all confined to small areas in the south-west. The four-
toed and the five-toed kangaroo-rats (Dipodomys and Pero-
dipus) are almost all peculiar to the south-western States.

Among the carnivores with a similar range may be men-
tioned the raccoon foxes (Bassariscus) and the western skunks
(Conepatus).

The most striking examples tenanting the ancient south-
western land areas must be looked for, as I remarked, among
the more sessile and slow-moving creatures. The reptiles and

amphibians yield good instances. Among the former the most
noteworthy is the so-called ‘‘ Gila monster,” a repulsive, stout,
thick-tailed lizard. It has gained the unenviable notoriety

202 ORIGIN OF LIFE IN AMERICA

of being the only poisonous lizard in existence. The genus
Heloderma, to which it belongs, ranges from Mexico, through
Arizona, to western Texas. No near relations of the Gila
monster are known, but it possesses some distant affinity to
a lizard living in Borneo.

Better known probably are the horned toads (Phrynosoma).
Owing to their greater activity they have been able to spread
much further north and east of their original centre of dis-
persal. The horned-toads are lizards belonging to the large
and important family Iguanidae which has a peculiar dis-
tribution suggestive of great antiquity, as I have already indi-
cated (p. 126). I mentioned that the family lived in America
as far back as Cretaceous times, and that beyond that con-
tinent it was only known from the Fiji Islands and Mada-
gascar. Leaving the latter out of consideration for reasons
stated (p. 126), we have only to discuss the origin of the Fiji
members of the family. The geological history of the Poly-
nesian fauna will be fully dealt with in a subsequent chapter.
I may mention, however, that I believe in the former exist-
ence of an ancient circum-Pacific belt of land which was
joined to south-western North America (Fig. 14), and that
the Iguanidae passed across this land during their wanderings
from America to Fiji or vice versa.

Let us turn from the active Iguanidae, and take, as an
example, a slowly-moving creature such as the Californian
limbless lizard Anniella. It inhabits barren sand-dunes, lying
buried in the sand and exposing only the anterior part of the
head.* Not only is it a reptile which spreads very slowly, but
it is eminently an animal requiring a continuous land surface
for its dispersal. As might be expected, the genus Anniella
is quite peculiar to the south-western States. No other
member of the family Anniellidae is known, though it is
closely related to the Anguidae, which are almost confined in
their distribution to America and Europe.

We also possess a single species of that remarkable family
of burrowing lizards, the Amphisbaenidae, in lower California
and Mexico, viz., Huchirotes biporus. It is a significant fact
that two peculiar genera of that ancient family occur in the

* Coe, W. R., and B. W. Kunkel, ‘‘ Californian Limbless Lizard,”
pp. 350—351.

ln ie EN ae a at a ee

BURROWING LIZARDS 203

two southern corners of North America, one (Rhineura)
in Florida, the other (Euchirotes) in Lower California and
Mexico. The only North American members of the blind
snakes (Glauconiidae) are limited in their range to the south-
western States. One of them (Glauconia dulcis) lives in
Mexico, New Mexico and Texas, the other (Glauconia humilis)
ranges from California as far as Arizona. These degenerate
worm-like creatures are entirely subterranean, and feed on
earthworms and larvae of insects. Hence their distribution
is of great zoogeographical value. Besides the districts re-
ferred to the family is found in the Lesser Antilles, Central
and South America, south-western Asia and Africa. That
these snakes should have passed all through the continent of
North America and through northern Asia in spreading from
South America to Africa or vice versa without leaving a trace
of their former wanderings seems to me very unlikely.
Yet geographical distribution of that kind is frequently ex-
plained by the supposition of a former Bering Strait land |
bridge offering the only means of land communication between
the Old World and the New. ‘There being no fossil evidence
to guide us, we must judge such cases altogether from the
present distribution, and it appears to me that an- ancient
land bridge across the mid-Atlantic explains the latter more
satisfactorily than the other hypothesis.

The theory of the former existence of such a land bridge is
not built upon a single instance of distribution. I have
mentioned many others in previous chapters, and I shall
allude to several in subsequent ones. One other striking
example may appropriately be mentioned here, viz., the dis-
tribution of. the boas (Boidae). These are mostly large and
active snakes. Nevertheless, they are related to the small
and slowly-moving blind snakes, because, like them, they pos-
sess rudiments of a hip-bone and hind limbs. Boas inhabit
all tropical and sub-tropical countries. Only in two dis-
tricts do they pass into temperate climates, viz., in the south-
western States of North America and in south-eastern
Europe. In these countries are found the two closely-allied.
genera Lichanura and Hryx. One of the North American
boas (Lichanura trivirgata) is confined to the extreme south
of Lower California, another to southern California and

—_
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204 ORIGIN OF LIFE IN AMERICA

Arizona, while a third, the rubber boa or silver snake actually
passes into Washington State and central Nevada.

The recent increase of dryness in the south-west has no
doubt affected the original fauna considerably. Semi-aquatic
forms and aquatic ones have either been destroyed or forced
to take refuge in the neighbouring States where climatic con-
ditions were more favourable. ‘To this cause may be atitri-
buted the present scarcity of amphibians in most of the south-
western districts, where many of them, we may presume,
originally had their headquarters. The only American mem-
ber of certain toads, which on account of the peculiar shape
of their tongues have been called Discoglossidae, occurs in
Washington State in western North America. This family
has always been looked upon with particular interest, because
to it belongs the solitary amphibian known from New Zealand.
This toad (Liopelma) must have reached New Zealand, ac-
cording to Dr. Stejneger,* before Cretaceous times by means
of a very ancient land connection with the north. The same
author expresses the opinion that the Himalayan Mountains,
or rather the region to the south-west of them, was the ori-
ginal home of these discoglossoid toads, and that they spread
from there to New Zealand and North America. On the latter
continent we still find, as I remarked, a single genus of the
Discoglossidae (Ascaphus). The present centre of dispersal
of these discoglossoid toads is southern Europe, since three
genera are found there, viz., Discoglossus, Alytes and Bom-
binator. The first two are strictly Huropean, whereas a single
species of Bombinator also inhabits northern China and Korea.
Considering the fact that these toads do not occur in south-
western Asia, and that both Discoglossus and Bombinator
have been found in European Miocene beds, the Mediter-
ranean Region seems more likely to have been the original
centre of dispersal than south-western Asia. At any rate,
that event leads us, no doubt, to the dim and distant past of
the early part of the Mesozoic Era.

The allied family Pelobatidae is likewise of great faunistic
interest, as the two genera Scaphiopus of North America and
Pelobates of Europe are only, distinguished by slight differ-

* Stejneger, L., “ Distribution of Discoglossoid Toads,” pp. 91—93.

SOUTH-WESTERN TOADS 205

ences. The spade-foot toads (Scaphiopus), as they have been
called, have their headquarters in Mexico and the south-
western States, whence they have spread northward along the
Pacific coast and eastward to the Atlantic States.* One
species, the hermit spade-foot (8. holbrooki) is worthy of
special note, owing to its occurrence on Martha’s Vineyard
Island, in view of the remark I previously. made (p. 183)
that this and other north-eastern islands are the remnants
of an ancient land mass formerly connected by land with the
mid-Atlantic land bridge.

The faunistic relationship between Europe and south-
western North America deserves an ample discussion, being
one of the most important and noteworthy features of the
American fauna. Besides the points already referred to
there are a few others which throw light on the nature and
origin of this relationship.

I do not intend to dwell on the merits of the various classi-
fications which have been adopted for the land mollusks. Even
if we base our system’ upon purely anatomical grounds, dif-
ferent points of view may sometimes give rise to considerable
differences in classification. Thus Dr. von Ihering + contends
that the family Helicidae, as far as North America ‘is con-
cerned, is entirely confined to the western States. Dr.
Pilsbry,{ on the other hand, in including Polygyra among
the Helicidae, naturally records for that family a very
different range.

Both authors agree in attaching great importance to the
molluscan fauna of the western and south-western States,
and both are inclined to attribute its origin to immigration
from Asia. That Dr. Pilsbry supposes the mollusks to have
wandered across an old Bering Strait land bridge, while Dr.
von Ihering § argues in favour of a much more southern
Oligocene land connection between eastern Asia and Cali-
fornia, is not perhaps of such fundamental importance. The
general agreement is all the more remarkable, as both
authors have formed radically different views on the interpre-

* Gadow, H., ‘‘ Mexican Amphibians and Reptiles,” p. 205.
+ Ihering, H. von, ‘‘ Verbreitung der Heliciden.”

» } Pilsbry, H. A., ‘“‘ Manual of Conchology,” Vol. IX., p. xxxii.
§ Ihering, H. von, “ Verbreitung der Heliciden,”’ p. 442.

— 206 ORIGIN OF LIFE IN AMERICA

tation of some anatomical facts. Dr. von Ihering supports
the opinions, upheld by almost all the prominent_European
conchologists, that the west American shells, which so greatly
resemble the European Ariantas and Campylaeas, are really
genetically connected with the latter. He even contends that
no anatomical distinction worth mentioning exists between
some of the American Epiphragmophoras and the European
Arianta. Dr. Pilsbry, on the other hand, does not recognise
any very intimate anatomical relationship between the Kuro-
pean and west American Helicidae, except in so far as he con-
siders both to be branches of an ancient south Asiatic stock.
As I shall explain later on, I concur with Dr. von Ihering,
Dr. Sandberger, Professor Oppenheim, Professor Boettger and
Dr. Kobelt in the opinion that many of the Antillean and
west American forms are intimately related to extinct and
recent European Helicidae. The great resemblance of the
shells of Arianta and some of the Epiphragmophoras alone
seem to imply a near relationship between them.

The genera Ashmunella, Sonorella and Oreohelix are quite
peculiar to south-western America, a large number of species
having been described by Dr. Pilsbry and Mr. Ferris * in a
series of articles contributed within the last few years to the
Proceedings of the Academy of Natural Sciences of Phila-
delphia. The same region contains many other distinct genera
of land mollusks. ‘The Urocoptidae, a family of snails some-
what resembling the Kuropean Clausilia in shape, and having
their headquarters in the Antilles, are represented by two
genera, viz., Holospira and Berendtia, peculiar to south-
western North America.

Of some interest is the occurrence in southern Mexico, in
lower California, and on the intervening islands, of many
species of the large and ponderous genus Bulimulus. The
difficulty of satisfactory identification unfortunately is such
that there is little agreement among the various authorities as
to the limits or range of species, nor is the nomenclature of
these shells in a more satisfactory position. All the same
as I shall mention later on, we can gather some useful hints
from their distribution.

* Pilsbry, H. A,, and J. H. Ferris, ‘‘ Mollusca of the South-Western 3

States.”

FAUNA OF CAPE REGION 207

The point, however, I wish to direct special attention to
is the fauna as a whole inhabiting the southern part of the
long peninsula of Lower California. This peninsula, for which
many people retain the Spanish name “‘ Baja California,”’ is
a narrow strip of broken mountainous land, nearly eight hun-
dred miles long, and averaging about fifty miles in width. On
the western side of this region there are a series of isolated
peaks or ridges rising to a height of about 2,000 feet. An
older range of mountains, composed of granite and gneiss, lies
along the eastern flank of the peninsula. Most of this vast
country is bare and desert-like, with a scanty flora, water
being difficult to obtain.* As soon as we enter what is called
the ‘‘ Cape Region ” all this is changed. Running water can
be procured throughout the whole year, in the larger cafions
at any rate, and this gives rise to an extremely rich and
exuberant vegetation. While almost the whole of the fauna
and flora of the peninsula are merely a continuation of those
of California and Arizona, having evidently passed into it from
the north and east, the southernmost tip, or Cape Region, has
an entirely different set of animals and'plants. I have already
alluded to the occurrence here of Euchirotes biporus, a very
peculiar burrowing lizard belonging to the ancient family of
Amphisbaenidae, and of the boa Lichanura trivirgata. Another
reptile, which is quite peculiar to the same district, is Cteno-
saura hemilopha. ‘This great lizard, of nearly two feet in
length, possessing a high crest along its back, a green head
and pale yellow body spotted with olive, brown and black, is a
most remarkable and striking object. The only near relations
of the burrowing lizard, and of the great active Ctenosaura,
live in south-western Mexico. But the Mexican forms do not
belong to the same species. We cannot, therefore, assume that
these lizards have been accidentally carried across the Gulf
of California, which has a width of about one hundred miles
near the tip of the peninsula. The genus Ctenosaura, it
may be mentioned, is related to Cyclura of the West Indies,
and Brachylophus of the Fiji and Friendly Islands, these
genera all belonging to the great family Iguanidae, which
has inhabited America since Cretaceous times (p. 202).+

* Merrill, G. P., ‘‘ Lower California.”
+ Denburgh, J. van, ‘‘ Herpetology of Lower California,” p. 78.

208 ORIGIN OF LIFE IN AMERICA

The flora of the Cape Region is sub-tropical, a considerable
proportion of the plants being West Indian. There are alsoa
few genera which do not occur elsewhere on the American
continent or the neighbouring islands. A small tree abun-
dant in the Cape district belongs to the genus Albizzia, which
is otherwise confined to Australia and the warmer parts of
Asia and Africa.* Although the lower Californian species is
quite distinct, its occurrence there might be attributed by
some naturalists to accidental distribution by marine currents
during some former period. No other occasional means
of transport could be thought of. But Albizzia is by no
means an isolated instance of floristic relationship between
the countries bordering the west and east sides of the Pacific
Ocean. Difficult problems of distribution of that nature are
apt to be looked upon as instances of accidental dispersal.
Yet these puzzling cases of distribution often supply us with
valuable clues with reference to possible changes of land and
water that may have taken place. That the Cape Region of
Lower California is really a fragment of an ancient land-mass
is suggested by the occurrence there of the burrowing lizard
Euchirotes, of two species of the fresh-water oligochaet worm
Kerria, and by a good many other faunistic features. Kerria
is only met with in that region, in the West Indies and in
southern South America.

Among the most interesting members of the Cape fauna
are the land shells of the genus Bulimulus above referred
to. Dr. Cooper,y in his series of valuable papers, only
mentions a few species found in that region, but he
alludes to the noteworthy fact that two of the Bulimuli
only live on the peninsula of Lower California, and in a similar
situation on the coast of southern South America, though quite
absent from the intervening moist tropical region. Dr. Dall,t
and more recently Dr. Pilsbry, have shown, however, that the
Cape species are not identical with the South American ones,
though extremely like them in general appearance, and that

they, together with those of southern Mexico and the interven-
ing islands, form a group by themselves. About twenty species

* Brandegee, T. 8., ‘‘ Flora of Baja California,” p. 222.
+ Cooper, J. G., ‘‘ Molluscs of Lower California,” p. 99.
t Dall, W. H., ‘‘ Bulimulus in Lower California.”

SNAILS OF CAPE REGION 209

of this genus of large snails are peculiar to the Cape Region,
several others being identical with Mexican ones. Some of
them have spread along the peninsula northward, yet it
seems certain that the Lower Californian centre of dispersal
lies in the Cape district, for no species occurs in California
proper. If we examine the range of the genus Bulimulus asa
whole, we find that its headquarters are in the West Indies.
From there it has travelled to eastern South America possibly |
across a very ancient land surface. Another branch has gone
westward and populated the distant Galapagos islands. A’
third stream apparently invaded the coast lands of South
America from the west, for we find numerous groups of Buli-
muli in certain western areas in Bolivia, Peru and Chile.
Still another section has struck directly westward across

southern Mexico to the southern parts of Lower California.

A couple of species have passed into Texas and further

east from this Mexican centre.

Considering that the closely related genus Placostylus
inhabits New Zealand, as well as a series of archipelagoes
between it and the Solomon Islands, it must be admitted that
in Bulimulus we have to deal with an almost archaic genus,

_ and that the land-masses and islands on which it is now found

are probably fragments of ancient continuous lands. Acci-
dental dispersal of shells has formed the subject of Mr.
Hedley’s * special study. Yet he shows that the species, par-
ticularly of the southern Placostylus, being heavy massive
Shells, are singularly unfitted for crossing distant seas by.
occasional means of dispersal. Hence he arrives at the con-
clusion that the Solomon and Fiji islands, the New Hebrides,
Loyalty Islands, New Caledonia, Norfolk Island, Lord Howe
Island and New Zealand form a zoological province, and are
to be considered as the fragments of a shattered continent.

A similar argument might be applied to Bulimulus, which is
so closely related to Placostylus. It seems permissible to
argue that the West Indies in early Mesozoic times were a
large united land-mass, that the latter was continued south-
eastward so as to join the archaic lands of eastern Brazil, that
it swept westward across what is now Central America out

* Hedley, C., ‘‘ Placostylus,” A Study in Ancient Geography, pp. 337—
339.

L.A. P

210 ORIGIN OF LIFE IN AMERICA

into the Pacific Ocean, and that wherever in Bolivia, Peru and
Chile we find groups of Bulimuli, the land on which they live
represents some portion or fragment of that ancient land
which once occupied part of the eastern Pacific Ocean. If we
had no other data in support of such theories, they would be
based on very slender evidence. But all this will be more
amply discussed when we come to deal with the general fauna
of the Galapagos Islands and western South America.

The only other point bearing on the westward extension of
the ancient ‘‘Antillea,” as the supposed West Indian continent
has been called, is the singular occurrence here and there
of traces indicating land westward of California. Along the
coast of southern California lies a little cluster of eight islands
which have lately attracted the attention of naturalists.
Now, as Mr. Greene informs us, on Santa Catalina Island
may be found Crossosoma, a plant so peculiar as almost to
represent a distinct natural order, and more closely related
to the Asiatic and Australian Dilleniaceae than to any plant
on the American Continent, except a single congener recently
discovered in south-eastern California. Speaking of Santa
Cruz, another of this group of small islands, he comments on
its unique feature in possessing no, less than forty-eight
species of plants not found on the opposite mainland and
expresses the opinion that the whole set of islands must have
a very peculiar geological origin and history. Species belong-
ing to distinctly Californian genera, like Dendromecon, Ksch-
scholtzia, Thysanocarpus and Zauschneria, abound in such
numbers as to suggest the question whether it was not from
these islands that the mainland plants of the same genera
were derived. The remarkable fact that Lyonothamnus,
Hazardia and the Lavateras, aJl of which have Asiatic or
Australian affinities, occur on these islands in several distinet
species, being quite unknown on the American continent,
makes Mr. Greene* wonder whether this group of islands
has not formerly been connected by land with some other
continent than America.

Surprising and apparently inexplicable as this feature may
seem, California and south-western North America generally

* Greene, E. L., “ Botany of Santa Cruz Island,” pp. 377—388.

EUROPEAN INVASION ont

reveal a still more extraordinary phenomenon in distribution.
We may imagine, and many people actually do, that the power
of wind and waves to carry objects from one part of the world
to another ‘is almost unlimited. One of the most striking
and remarkable characters of California, however, is its very.
close faunistic affinity with western Europe. Hven the most
enthusiastic supporter of the flotsam-jetsam theory will feel
that some other cause than this must have been responsible in
producing this effect. A former land connection between the
two regions, without others being affected, seems out of the
question.. Yet almost all those who have endeavoured to
explain the origin of this western fauna have preferred
to choose the old Bering Strait land connection as offer-
ing a safe passage to Huropean animals, rather than
disturbing the general arrangement of the existing oceans
and continents. If the faunistic resemblance of Cali-
fornia to western Europe had really been caused by a
migration of animals from! one area to the other across the
whole Asiatic continent, eastern Asia ought surely to show
affinity with California to a much more pronounced degree
than western Europe does. As a matter of fact,. certain
groups in California are distinctly eastern Asiatic in affinity,
as I have just mentioned, while others are just as clearly,
‘south and west European in character. I have given a few
instances already of these faunistic relationships, and further
evidence will now be adduced in support of this statement.

I think it was the snail Arianta arbustorum, so prominently
alluded to in my work on European animals, which first
drew the attention of American zoologists to this relation-
ship, for, as already remarked, a snail extremely similar in
appearance lives in California. Even Dr. Pilsbry * admits
that the resemblance in shell characters of the Californian and
Huropean species is astonishing, although he adds that it
is due to a purely secondary modification that these shells have
been moulded to a deceptive likeness, the genitalia having
been left unchanged to tell more faithfully the story of their
lineage. Having made an anatomical study of this Californian
Arianta-like group, Dr. Pilsbry arrives at the conclusion that

* Pisbry, H. A., ‘‘ Manual of Conchology,” IX., p. 196.
PQ

212 ORIGIN OF LIFE IN AMERICA

the latter belongs to the same great family Helicidae as the
European Arianta, but that otherwise it is quite unrelated
to it. He places the Californian forms, therefore, into the
genus Hpiphragmophora, contending that its nearest rela-
tions are the Helices of Japan. In another place (p. 46) he
adds the remark that it is unnecessary to throw land bridges
across the depths of the Atlantic and Pacific Oceans to account
for the distribution of Helices. Such hypotheses, he thinks,
are contrary to many facts indicating that such groups of
snails as are common to America and Kurope have radiated
from an Oriental centre westward to Europe and eastward,
by way of a former Bering Strait land bridge, to America.
Yet Dr. Pilsbry’s conclusions, as I have already mentioned,
are contested by Dr. von Ihering likewise on anatomical
grounds. Although Dr. Pilsbry maintains that his opponent
bases his deductions on figures and not dissections (p. 195),
Dr. von Ihering, in a recently published paper, again insists
that, after having made a careful anatomical investigation of
Arianta, (or Helicigona as he calls it,) and the American
Epiphragmophora, he could perceive no difference worth men-
tioning between the two. Hence Dr. von Thering’s* opinion
is that the American Helices, which are now generally known
under the name of E;piphragmophora, and which are entirely
confined to the Pacific coast of America, possess their nearest
relations not in Asia but in western Europe.

Let us take another group, that of the well-known Euro-
pean family of slugs, the Arionidae. In 1896 Messrs. Pilsbry
and Vanatta + showed by anatomical investigations that the
American slugs Ariolimax and Aphallarion belong to this
family. Later on the same writers added the genera
Anadenulus, Hemphillia, Hesperarion and Prophysaon to
this list. The whole of this great assembly of Arionidae
is quite confined to the Pacific region between British
Columbia and southern California. No other slug of this
family has as yet been discovered anywhere in the New
World, except one or two European species in the north-
eastern States, which may either have been introduced

* Thering, H. von, ‘‘ System der Heliciden,” p. 422.

+ Pilsbry, H. A., and E. G. Vanatta, “‘ Revision of North American
Slugs.”

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SNAILS AND SLUGS OF CALIFORNIA — 213

or have crossed over by a former North Atlantic land bridge.
In western Europe and north Africa we have the four genera
Arion, Geomalacus, Ariunculus and Letourneuxia. Only the
first of these has a wide range, one species extending through
Russia to northern Siberia. In Asia only a single genus
(Anadenus) of the family is known, inhabiting the Hima-
layan Mountains and China. The Arionidae thus have a most
discontinuous range, and their origin and dispersal form an
interesting problem. Since Geomalacus and Letourneuxia
are confined to the western borders of Europe and North
Africa, and Arion obviously has its headquarters in the same
region, Professor Simroth * argued that the European Ario-
nidae had either originated on a sunken land which lay out
in the Atlantic, or wandered across an ancient Atlantis from
western America. Dr. Pilsbry + also is in favour of an
American genesis for the Arionidae, but he believes that
the ancestors of the Old World genera just alluded to
must have crossed over to Asia by means of a former
Alaskan land bridge, and then have wandered along, dropping
Anadenus on the way, until they finally reached western
Europe. Of the two theories Professor Simroth’s appears
to me the more plausible one. And his hypothesis is
strengthened by the occurrence in south-western North
America of a species of slug either identical or very closely
related to a Huropean one, viz., Amalia hewstoni. The Huro-
pean Amalia (Milax) gagates must be regarded as an exceed-
ingly ancient species, certainly dating back to beyond Tertiary
times. Geological evidence for such a belief there is none,
nor could we expect to find the remains of slugs in ancient
deposits. In a matter of that kind we have to rely purely on
distributional evidence, That Amalia gagates could be trans-
ported to any island from the mainland by the ordinary means
of dispersal is out of the question. It can only have
reached its present habitat on many very remote islands by
human introduction or by former land connections with the
mainland. It is by no means a slug that congregates near
human habitations, nor is it commonly found among vegeta- —
bles like some of the Limaces and Arions. Yet it occurs in

* Simroth, H., ‘ Nacktschnecken Russlands,” p. 60.
+ Pilsbry, H. A., ‘‘ Phylogeny of Arionidae,” p. 103. :

214 ORIGIN OF LIFE IN AMERICA

variously modified forms on the islands of Madeira, Sicily,
Sardinia and Teneriffe, on the Azores, the Cape Verde islands,
St. Helena, Tristan d’Acunha and Bermuda. It has never
been reported from any of the West Indian islands, Central
America or the southern States of North America. In western
North America it has a wide range, being known as Amalia
hewstoni, from British Columbia to Mexico. On the east

coast it occurs only along the coast of Massachusetts and New

York, exactly where so many other members of an ancient
fauna reside. In Asia, except Asia Minor, no Amalia has
hitherto been discovered. In Africa it is only met with along
the north coast and in Cape Colony (A. ponsonbyi). From
south Australia a similar form has been described as Amalia
pectinata, while others occur in New Zealand and the Sand-
wich islands. Most zoologists will insist that such an enor-
mously wide and discontinuous range of a species, though
exhibiting distinctive characters in its various habitats, can
only be due to artificial introduction by man. My own opinion
is that it has reached all the localities referred to by the
natural means of progression on land during a long series of
geological periods, and Professor Simroth,* the best living
authority on slugs, shares the same view. As far as its occur-
rence in western North America is concerned, Professor Sim-
roth’s Atlantis, a land bridge connecting Portugal with the
West Indies and the lands beyond it across the Atlantic,
would suit our purpose. The slug’s absence from the Antilles
might be due to the fact that it became extinct there during
the extensive submergence which the West Indian area has
undergone in Tertiary times.

The eminent‘authority on butterflies and moths, Dr. Pagen-
stecher,y tells us that California possesses an independent
character among the North American fauna, in being more
nearly related to Europe than to the eastern States. With
the exception of Ctenucha and Agarista all the genera are
European, while Pyrameis atalanta, P. cardui, Vanessa
antiopa, Arctia caja, Phragmatobia fuliginosa, Scoliopteryx
libatrix, Brachionycha nubeculosa, Amphipyra pyramidea and
Agrotis exclamationis are common to California and Europe.

* Simroth, H., ‘“‘ Pendulations Theorie,” p. 92.
+ Pagenstecher, A., “ Verbreitung d. Schmetterlinge,” p. 359.

= a a a . ~ —

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BUTTERFLIES OF CALIFORNIA _—215

Among the most abundant beetles in California there

_ is a group of flightless forms which when touched will emit

a pungent, oily secretion. Owing to their curious habit of
elevating their bodies when alarmed they have received in the
west the popular name of “ circus bugs.” Now this section
Eleodinae of the large family’ Tenebrionidae are, in North
America, quite peculiar to the south-west. A few species have
spread northward into Washington State and eastward as far
as the Mississippi. The great mass of these thick-bodied oily
creatures lives in Mexico and California, where, according to
Mr. Blaisdell,* they have probably originated. The only near
relation of this south-western group in the New World is the
genus Nycterinus, which is peculiar to Chile, But throughout
the Mediterranean Region we meet with a very large number
of similar beetles, commonly called “oil beetles,” and
although many of them are also found in Persia, Turkestan,
Central Asia and even China, south-eastern Hurope must be
looked upon as the headquarters of the gang Blaps, to which
they belong.

The same family Tenebrionidae also offers instances of
intimate relationship between the Antilles or Central America
and southern Europe. I need only recall the American
Gnathocerus maxillosus which likewise inhabits Madeira, the
Canary and Mediterranean islands, as well as Sitophagus
hololeptoides of Central and South America, the Antilles and
Madeira. |

Dr. Kolbe + mentions similar examples of distribution
among the coprophagous lamellicorn beetles. Thus Oniti-
cellus and Glaresis are quite peculiar to the south-west in
North America, whereas in Europe they are confined to the
Mediterranean Region. Only the former has spread further
southward into Africa and eastward into Asia.

Of all the insects, faunistically the most interesting are
the ants. In my work on Kuropean animals I alluded to
Stenamma westwoodi as one of the members of the Lusitanian
fauna, which penetrated as far north as south-western Ire-
land. The same species is met with in America in a few
varieties. One lives in California, the other in British

* Blaisdell, F. E., ‘ Hleodinae of the United States,’’ pp. 28—29.
t+ Kolbe, H. J., “ Verbreitung d. Coprophagen Lamellicornier,” p. 499.

216 ORIGIN OF LIFE IN AMERICA

Columbia, the third in the north-east.* Honey-ants, at least
certain members of their colonies, possess the faculty of
storing quantities of honey within their bodies, which swell
up to a great size, and on that account are somewhat remark-
able objects. In North America two species of honey-ants
occur, namely, Myrmeocystus melliger and M. mexicanus,
both being confined to Mexico, Arizona and the neighbouring
regions. The other species of the genus Myrmeocystus in-
habit the Mediterranean Region and further east as far as
central Asia.t In southern Europe a soft, velvety ant is
found belonging to the genus Liometopum. The same species
was likewise supposed to inhabit California, but Professor
Wheeler { found that although the two forms are very
closely related, the American differs slightly in shape and
even in its habits from the European species. Whereas the
former constructs its nests underground, the latter utilises
for that purpose the abandoned burrows of beetles under the
bark of trees. Hence he calls the American ant, Liometopum
apiculatum. It is limited in its range to California and
‘Mexico. Only two other species of Liometopum are known.
One, (Li. microcephalum), as I mentioned, lives in southern
Europe, the other (Li. lindgreeni) in Assam. It is not often
that we actually become acquainted with the extinct ancestors
of such interesting invertebrates as these. But fossil forms
of Liometopum have been discovered, according to Dr. Hand-
lirsch§ in the Lower Miocene of Croatia and the Oligocene of
Colorado. Even in Tertiary times the genus seems to have
occupied much the same localities as it does to-day; it only
spread formerly further north no doubt owing to the more
favourable climatic conditions then prevailing.

Many other similar instances might be quoted. I will only
allude to one more. The two well-known European ants
Formica cinerea and Formica rufibarbis had been reported
from the south-western States of North America, but Pro-
fessor Emery doubted the correctness of the identification
until Professor Wheeler sent him American specimens. Both

* Emery, ©., ‘‘ Nordamerikanische Ameisenfauna,”’ p. 299.
+ Wheeler, W. M., “ Honey Ants,” p. 347.

t Wheeler, W. M., “ North American Liometopum,”’ p. 321.
§ Handlirsch, A., “‘ Die Fossilen Insekten,”’ p. 870.

EUROPEAN ANTS IN CALIFORNIA 217

species must have been established in America for long periods
past, as their range extends inland in a north-eastward direc-
tion beyond the Rocky Mountains.

Instances of specific identity in the two widely separated
regions of California and southern Europe are to be found
in several groups. Professor Kraepelin * reports, for example,
that the scolopendrid Theatops erythrocephalus is such a
ease. From California it has spread as far as Oregon.
In southern Europe it is known from Portugal, Italy,
Dalmatia and Hungary. The genus Theatops is confined to
North America, including the Sandwich islands, and southern
Europe.

A member of the order Palpigradi, a minute creature
somewhat resembling a scorpion in shape, has been observed
in Texas and named Koenenia wheeleri after Professor
Wheeler. Two other members of the genus are known from
South America, one from Chile, the other from Paraguay.
But the nearest relations of the North American form are evi-
dently Koenenia mirabilis of Sicily and Tunis, and K. draco of
the Balearic islands. The only two other species live in Siam.f
We thus have in this ancient group again the same intimate
affinity between southern Europe and south-western North
America as in some ants, beetles and butterflies, showing
clearly that the same potent cause, which is certainly not acci-
dental distribution, has contributed to bring it about. In
order, however, to make quite sure that these are genuine
instances of migration on a land surface, and not due to
occasional or accidental transport, let us now examine care-
fully the range of a large fresh-water form and endeavour to
trace its origin.

Fresh-water crayfishes, as Dr. Ortmann remarks in his
excellent account of them, do not possess any exceptional
means of dispersal. They are restricted to fresh water and
cannot exist out of it, neither in salt water nor on land.
Moreover, they do not possess, during any stage of their life
history, means or devices which might favour their passive
transport from one fresh-water system to another. The whole
character of their range is opposed to the assumption that

* Kraepelin, K., “ Revision der Scolopendriden,” pp. 64—66.
+ Hansen, H. J., ‘‘On Koenenia.”’

218 ORIGIN OF LIFE IN AMERICA

their dispersal has been caused by any exceptional or abnormal
means of transport. Few zoologists will consequently dis-
agree with Dr. Ortmann’s * assertion that fresh-water cray-
fishes are among the most important animals in so far as the
study of their distribution elucidates past changes of land
and water over the globe. The crayfishes have been brought
into great prominence by Professor Huxley’s well-known
treatise on the subject. More recently it is principally in
America that their structure and distribution have been
studied with great assiduity. Dr. Faxon was the first to
recognise that besides the American genera Potamobius
(Astacus) and Cambarus, there is a third genus of fresh-
water crayfishes which inhabits north-eastern Asia. The
latter, it is true, is only ‘considered a sub-genus of Pota-
mobius by Dr. Faxon and also by Dr. Ortmann, but, as
Mr. Stebbing t has pointed out, its intermediate position
between Potamobius and Cambarus entitles it to rank as the
distinct genus Cambaroides.

The geographical distribution of these crayfishes (Pota--
mobiidae) is very suggestive and interesting. Europe is the
headquarters of the old and well-known genus Astacus, which
name, in the unfortunate search for priority, has had to
give way to Potamobius. The genus ranges practically
throughout Europe, from north to south and from east to
west, and only very little beyond it. Beyond the Caucasus
it crosses into Transcaucasia, Turkestan and western Siberia.
It is quite unknown in the remainder of Asia. In the rivers
of eastern Asia, in Korea, Japan and eastern Siberia we meet
only with members of the small group Cambaroides referred
to. The somewhat close resemblance of this Asiatic genus
to the American Cambarus does not point to blood relation-
ship, according to Dr. Ortmann, merely to convergence. In
America we find not only Cambarus, but also Potamobius, the
European crayfish, the latter genus being in America entirely,
confined to the western States. Professor Huxley and Dr.
Faxon both urged that the American species of Potamobius re-
sembled the European crayfishes much more than the Asiatic

* Ortmann, A. E., “ Distribution of Freshwater Decapods,” pp. 315—316.

+ Faxon, W., “ Revision of Astacidae.”
{ Stebbing, T. R. R., “Crustacea,” p. 208.

—_

CRAYFISHES IN THE SOUTH-WEST 219

ones, yet, like Dr. Ortmann, they maintained that Europe was
supplied with its crayfish fauna from the East. In his lucid
essay on this subject, Dr. Ortmann argues that a primitive
group of Potamobiidae, ancestral to all the living ones, must
formerly have existed in eastern Asia, which region should
be regarded as the centre of dispersal of the family. This
ancient group, he thinks, sent one branch westward to Kurope
and another eastward across the old Bering Strait land bridge
to western North America. Thus, three centres of dispersal
gradually originated in which the old stock developed on
independent lines. The middle one changed to Cambaroides,
while the two branches retained the ancient characters. From
the American branch eventually originated Cambarus, which
spread eastward into the eastern States of North America
(see pp. 289—91). |

I accepted Dr. Ortmann’s explanation in my work on Euro-
pean animals as an hypothesis, which satisfactorily accounted
for the present distribution of the Potamobiidae. Doubts,
however, have since arisen in my mind as to whether there
is not a better theory. The more I studied the problem the
less I felt disposed to agree with Dr. Ortmann’s explanation.
Why should the old stock, for instance, have become modified
into Cambaroides in its original centre of dispersal, while still
flourishing in two centres enormously distant from one
another ? And these two new centres were reached after many,
struggles and vicissitudes, after long and weary travels, prob-
ably through hundreds of miles of unsuitable ground. One
would imagine the two distant branches to have become
more and more unlike one another. Five species of the
old stock Potamobius still inhabit the streams of western
America, from California in the south to Alaska in the north.
If Dr. Ortmann’s theory were the correct one, the centre of
dispersal of the more modern genus Cambarus, which has
developed from some member of the old stock, ought to be in
north-western America. LEverything, nevertheless, points to
the conclusion that the new genus Cambarus originated in
Mexico, and Dr. Ortmann (p. 291) is of that opinion, having
recently supported it by means of many additional facts of

- distribution.*

* Ortmann, A. E., “ Affinities of Cambarus.”’

220 ORIGIN OF LIFE IN AMERICA

It is to south-western North America, therefore, that we
must look for the original home of the ancestral group of
Potamobius. They still inhabit that area, and may have
spread from there northward to Alaska, and even further
to north-eastern Asia, eventually giving rise to Cambaroides.
Taking these and many other remarkable facts of dis-
tribution into consideration, it appears to me quite pos-
sible that the presence of the crayfish Potamobius in
Europe and North America, and its occurrence in the
western parts only of the latter continent, may be due to

an ancient land connection which, as already suggested, —

joined western Europe and Mexico by way of the West Indies.
Whether the family originated in North America or in Europe
will have to form the subject for future researches. That this
migration took place in very remote times, is implied by the
fact that Cambarus primaevus (which Dr. Faxon believes to
be a Potamobius), occurs in the Eocene beds of western
Wyoming. If such a land bridge as that alluded to actually
existed in early Tertiary or late Mesozoic times, it may be
asked why do we not meet with any members of the genus
Potamobius in the streams of the West Indian islands? To
this we may answer that geologists are practically agreed
that in post-Hocene, or even during Eocene times, the whole
area of the Antilles was greatly submerged, so that we may
suppose that the ancient fauna that wandered across that area
from either Europe or North America was largely extermi-
nated. That the islands were subsequently again connected
with the mainland we may assume from the presence of
Cambarus cubensis, a crayfish peculiar to the island of Cuba.

My views as to the nature and extent of that mid-Atlantic
land bridge will be more fully explained in the chapter dealing
with the West Indies. The presence or absence of such a land
connection, however, is of such vital importance to the eluci-
dation of the phenomena of distribution, that I may be ex-
cused for quoting still further examples of animals whose
range throws light on the solution of this problem.

In the beginning of this chapter (p. 205) I mentioned the
fact that the spade-foot toads (Scaphiopus) have their head-
quarters in Mexico and the south-western States of North
America, and that their nearest relations are the members

—

ptumen

"covers

FAUNISTIC PROBLEMS 221

of the genus Pelobates which inhabit Europe. Only a
single species (P. syriacus) has been discovered in Asia
Minor. The others extend from western Kurope to the
Caspian. Another genus (Pelodytes) of the family Pelo-
batidae has one species in Portugal and a second in the
Caucasus. All the other genera of the family are found in
the East, and are more remotely akin to Scaphiopus than
Pelobates is. Hence we may conclude that the distribution
of these two genera is distinctly favourable to the suggested
trans-Atlantic land bridge.

Another interesting amphibian that I have alluded to
(p. 187) is the newt Spelerpes, which’, with the exception of
a single European species, is peculiar to America (see Fig. 8).
The centre of dispersal certainly lies in Mexico, from which
country various sections have spread northward into the
States, southward as far as Peru, and eastward to the island of
Haiti. That this discontinuous distribution could not have
been brought about under existing geographical conditions is
evident, nevertheless, since no fossil Spelerpes are known, we
can only judge of the age of the genus from its distribution.
Dr. Gadow * suggests the Oligocene Period, and thinks that a
north-Atlantic land connection, such as the one I have de-
scribed in the first chapter of this work, from Labrador to
Scotland via Greenland, might have brought about the exist-
ing range of Spelerpes. Since the single Huropean species
inhabits only Sardinia and the mountains bordering the Gulf
of Genoa, while most suitable ground for its existence is found
further north, I cannot admit that Spelerpes fuscus reached
| Europe in that manner. The land bridge by which it crossed
_ the Atlantic must have lain much further south.

I have already alluded to the fact (p. 173), that there
is apparently a south-western and a south-eastern form
of the American glass snake (Ophisaurus ventralis), and
that both of them extend northward for considerable dis-
tances. The only other members of the genus are the
European glass snake (Ophisaurus apus), which inhabits the
Mediterranean region and is very like the American, and the

_ Asiatic species, which is found from the eastern Himalayas
| to Burma.

. = * Gadow, H., “ Mexican Amphibians and Reptiles,” p. 244.

222 ORIGIN OF LIFE IN AMERICA

Dr. Ruthven’s valuable researches into the origin and dis-
tribution of the garter-snakes (Thamnophis = Eutenia) have
been discussed in an earlier chapter (p. 128). I need only
restate that he traces the home of the genus to northern
Mexico. And Thamnophis is clearly an offshoot from the
older water-snakes (Tropidonotus), which have almost a
world-wide range. As in the case of Potamobius and
Cambarus, both genera seem to have spread northward
from their south-western centre, the south-western Tropi-
donotus validus having its nearest relation in the Sar-
dinian Tropidonotus viperinus. Dr. Brown * recognised per-
fectly that the affinity between such forms as the European
and American species of Tropidonotus necessitated the exist-
ence of a former land bridge between the two continents.
He also urged that the existence of this bridge must have
coincided with a warm climate in the north, for he naturally
assumed that only in the extreme north could there have been
such a land connection. Its geological age he fixes at about
the early Miocene, though he believes many of the present

genera to have been in existence even in Eocene times. —

My objection to Dr. Brown’s theory is that we have no evi-
dence in Hurope of a southward advance of Tropidonotus
from a former northern centre of distribution, nor are the
northern species in both continents more closely related to
one another than the southern species. The former existence
of a more southern trans-Atlantic land bridge in early
Tertiary times, on the other hand, is supported by such a
number of palaeontological facts, as we shall learn later on,
that the evidence is overwhelmingly in its favour.

It is quite possible that the western tortoise Clemmys
marmorata, or its ancestors, for the genus, as I mentioned
(p. 183), has inhabited south-western North America since
Kocene times, has spread across the same mid-Atlantic land
bridge to western Hurope, a near relation (Clemmys leprosa)
being peculiar to Portugal, Spain and north-western Africa.

That all these animals living in south-western North
America and western Europe which show close relationship,
are relicts of very remote geological times is rendered prob-

* Brown, A, E., “ Post-Glacial Nearctic Centres,” p. 466.

MAMMALIAN AFFINITIES 298

able, partly from palacontological evidence, and partly from

other methods of reasoning. That most of them trace their

origin in America or Europe to the former existence of a
direct land bridge across the mid-Atlantic seems also obvious.
Yet many geologists are very strongly opposed to a theo-
retical bridging of the Atlantic. Nothing short of a well-
marked mammalian affinity between the two areas alluded to
will satisfy them. We can produce little of such evidence, be-
cause most groups of mammals have changed very rapidly
during the course of the Tertiary Hra. A few, however,
such as the rodents, appear to have the faculty of preserving
their ancestral characters for longer periods, and some,
apparently, have undergone little change since remote times.

There are two instances, one among the voles, the other
among the hare family, that seem to point to the existence of
the land connection just discussed, and these cases may pos-
sibly throw more light on the age of the land bridge than the
invertebrates or reptiles can do. Professor Tullberg * con-

| tends that the meadow voles (Arvicola=Microtus) only entered

Kurope in Pliocene times from Asia, where they had already
existed for some time previously. He also expressed the
opinion that these voles subsequently crossed over to America
from Europe by a north-Atlantic land connection, which I
presume must be the Scotland-Greenland-Labrador bridge.
We know very little of fossil meadow voles. If Professor
Schlosser is correct in his assertion that only geological re-
searches can give us any clues as to former changes of
land and water, and that zoogeography cannot do so, the
meadow voles can teach us very little.

Yet if we examine the present range of one of the sub-
genera of meadow voles, such as Pitymys, we find it very
remarkable and instructive. One species lives on the Mont
d’Or in France, at a height of over 4,000 feet, another on one
of the southern Alpine spurs, at a height of 6,000 feet. De
Sélys long ago described a species (Pitymys incertus) from
the St. Gothard mountain, a locality which is over 7,000
feet high; another related form inhabits the Pic du. Midi in
the Pyrenees, and still another a mountain in Sicily. Quite

* Tullberg, T., “System der Nagetiere,” p. 499.

224 ORIGIN OF LIFE IN AMERICA

a number of species are now known from southern Spain and
Portugal, owing to the researches of Mr. Thomas, Mr. Miller
and Dr. Forsyth Major. To judge from its recent distribu-
tion, these voles of the sub-genus or genus Pitymys ought
to be of very great antiquity, yet not a single fossil specimen
has ever been found. The most remarkable fact in the dis-
tribution of Pitymys is that it is entirely confined to Hurope
in the Old World, whereas across the Atlantic, in Mexico,
we again meet with a member of this group known as the
Jalapa meadow vole (Pitymys quasitor). It lives there at an
altitude of about 5,000 feet. Only two other species are
known from North America, one (P. nemoralis) from the
Boston Mountains in the Indian Territory, the other from
certain areas in the eastern States. The latter (P. pine-
torum) occurs from southern Florida to Carolina, a variety
of it on the Allegheny Mountains, and another from Long
Island to the borders of Illinois. The range of the three
American species is disconnected, and confined to Mexico and
the United States. What is the relationship of these species
to one another, and which is the oldest, will have to be deter-
mined by future researches, also whether the extinct species
discovered in Pennsylvania by Professor Cope really belongs
to Pitymys or Microtus proper. At any rate, there is nothing
in the range of Pitymys that might lead us to suspect that it
entered North America from the north-west, no member of
the group having as yet been found in any part of Canada or
Alaska. In Europe Pitymys is unknown in the north-west,
whereas a number of species inhabit the south-west. Hence
the American group of Pitymys may possibly have been de-
rived from one or more species which crossed the Atlantic
on the land connection above referred to.

The hare family (Leporidae), as a whole, has a very wide
distribution in Europe, Asia, Africa and America, but some
of the sub-genera, which are gradually being raised to the
higher dignity of genera, are confined within certain circum-
scribed limits. In his study on the recent and fossil Lago-
morpha, Dr. Forsyth Major * comes to the conclusion that this
family might conveniently be divided, according to the osteo-

* Major, Forsyth, “Fossil and recent Lagomorpha,” pp. 614—516.

FF) fo eS, ae =" 2 7.

AMERICAN RABBITS ~. 225

logical characters of its members, into two groups, viz., the
Caprolagus and Lepus groups. The first of these, which is of
particular interest, contains the four genera Caprolagus, Neso-
lagus, Oryctolagus and Sylvilagus. Caprolagus lives in Asia,
and is likewise represented in Huropean Pliocene beds. The
second is peculiar to the island of Sumatra. The third, which
includes the European rabbit, has an extremely discontinuous
range; being confined, according to Dr. Major, to the Mediter-
ranean Region, Western Europe and South Africa. Sylvi-
lagus is peculiar to America. From its very scattered range
the Caprolagus group of hares and rabbits would seem to
be of ancient lineage. Ina more recent study of the hares and
their allies, Dr. Lyon recognised nine genera of this group.
He separates the South African form of rabbit from the
Kuropean, raises several of Dr. Forsyth Major’s sub-genera
to the rank of genera, and adds the new genus Pentalagus
from the Liu Kiu islands near Japan. Whereas Dr. Forsyth
Major recognised four sub-genera of the American Sylvi-
lagus, Dr. Lyon places only two sub-genera under this genus.
Although Dr. Lyon gives a fuller and more complete
account of all parts of the skeleton in the different species of
Leporidae than Dr. Forsyth Major. He was moreover able to
detect certain prominent structural characters, which appar-
ently escaped Dr. Major’s notice. While the latter believed
in the close relationship of the European and the Cape rabbits,
Dr. Lyon* demonstrates that the nearest relation of the
former is the American Sylvilagus. The skulls of the two
genera, taken as a whole, are not markedly different, and the
teeth are essentially alike.

The European rabbit also possesses marked affinities with
Limnolagus, another American genus of rabbits, but not with
any of the Old World genera of the family. The genus
Oryctolagus, with its single species the European rabbit
(O. cuniculus) is confined to the countries round the Medi-
terranean. Only in France, that is to say, in western Europe,
is there a tendency to a northward extension of this range,
and in that it resembles a great many other typically Medi-
terranean animals. Its relation, Sylvilagus, ranges from the

™ Lyon, M. W., “The Hares and their Allies,” p. 406.
L.A. Q

226 ORIGIN OF LIFE IN AMERICA

northern border of the United States, all over the States
and Central America. In South America its exact distribu-
tion is still unknown, but it possibly reaches Patagonia. The
cotton-tails and brush rabbits (Limnolagus) occur only in
the southern States. We thus note the remarkable fact
that rabbits of close relationship are separated in one
direction by a comparatively short intervening space of sea
water, in the other by a very much longer area of almost
uninterrupted land, which is tenanted almost exclusively by
the more distantly related hares. The other American
rabbits, the pigmy rabbit (Brachylagus), and the Popocatepetl
rabbit (Romerolagus), are confined to Mexico and western
North America. The south-western region must, therefore,
be looked upon as the centre of dispersal of the rabbits.*

The fossil history of the American Leporidae is meagre in
the extreme. Only a few Oligocene species of the extinct
Palaeolagus are known, and these, according to Dr. Major,
seem to be ancestral to the modern genus Lepus. No fore-
runner of the existing Sylvilagus and Oryctolagus has yet been
found. It possibly lived in south-western North America
in early Tertiary times. Palaeolagus already possesses in-
cisors of the modern type, and Dr. Matthew thinks that we
may look among Hocene rodents, or even in the fauna of
Cretaceous deposits, for guidance as to the manner of evolu-
tion of the teeth of the Lagomorpha.t

This leads us. back once more to the general consideration
of the American Tertiary deposits and the affinities of their
fauna. ‘These deposits, above all, ought to yield indications
as to whether there was a direct land connection between
south-western North America and western Europe across the
mid-Atlantic, such as the one I advocated.

We are confronted in America by two grand problems,
says Professor Osborn,{ one being the chronological correla-
tion of the purely fresh-water horizons with one another, the
other the chronological correlation of American horizons with
Eurasiatic vertebrate horizons. When these are worked out,
continues the same writer, we shall be able to establish a

* Nelson, E. W., “ Rabbits of North America.”
+ Matthew, W. D., “ A Horned Rodent from Colorado,” p. 307.
{t Osborn, H, F., “‘ Cenozoic Mammal Horizons,” pp. 29—30.

ON ATLANTIC LAND BRIDGES ro Say

complete and very accurate geological time scale for the entire
Tertiary Era, and to speak with precision regarding the time
of successive migrations. Much still remains to be done to
establish the approximate ages of the various Tertiary de-
posits in Europe and America before we can definitely say
whether a certain group of mammals made its first appearance
in Europe or'in America. Possibly we may not reach such
a state of knowledge for a long time to come.

In New Mexico what are known as the “ Puerco” and the
“Torrejon’’ formations have yielded remains of archaic
mammals;.some of which are related to mammals occurring
in late Mesozoic or early Tertiary deposits of Patagonia, others
indicating affinity with those of a similar age in France.
Now, as Professor Depéret tells us, it is inadmissible to argue
that mammals so nearly akin to each other could have arisen
independently in three distinct centres, in Patagonia, in
south-western North America and in France. We can only
explain these palaeontological affinities by migrations from
one area to the other. Professor Depéret * believes that the
cradle of these early placental mammals was in North
America, and that they crossed over to Europe by utilising
the “territories of the North Atlantic which had risen from
the sea.” This is a somewhat vague statement, yet it indi-
cates clearly that the great French palaeontologist had in his
mind the existence, in these remote geological times, of some
kind of north Atlantic land bridge. He does not explain how
the North American mammals reached Patagonia, but Pro-
fessor Osborn speaks distinctly of a, contemporary, that is
to say, early Eocene or previous (Cretaceous) land connection
between North America and South America, and he actually
places it in the same position as it occupies at present (see
Fig. 21). I propose to discuss it later on. At present we may
confine ourselves strictly to the European affinities of North
America.

A momentous change occurs, according to Professor
Osborn, in the succeeding Wasatch formation of New Mexico
and Wyoming. ‘The parallelism of similar stages in the
archaic mammals of western Europe and south-western

* Depéret, C., “Transformations of the Animal World,” pp. 308—309.
t Osborn, H. F., “Cenozoic Mammal Horizons,” p. 33.

Q 2

i AE

nem

228 ORIGIN OF LIFE IN AMERICA

North America remains as before. The new feature is the
sudden appearance of true carnivores, ungulates, primates
and rodents. JI have already referred to Eohippus
(p. 147) as an early representative of the horse family.
Another modern family which traces its origin back to
these remote times is that of the tapirs, for the Eocene
Systemodon has all the characters peculiar to the recent
Tapiridae. Whether the early primates were lemurs or true
monkeys is as-yet undecided. The rodents all belong to the
extinct Ischyromyidae, which Dr. Matthew * believes to
have been arboreal creatures, somewhat resembling squirrels
in shape, although more nearly related to the peculiar and
typically west American sewellel (Aplodontia).

This sudden and simultaneous appearance of modern
families of mammals, along with several extinct ones, in
western Europe and south-western North America is very
striking, and has to be accounted for. To begin with, we
have to determine the origin, or original centre of dispersal
of this fauna. Professor Osborn feels certain that this fauna
originated neither in Africa nor in South America. There
remain, he thinks, four possible sources. They may have
come from the Great Plains Region of North America, from
the more northerly American Mountain Region, from the
northerly Eurasiatic Region, or from the American-Asiatic
land-mass. He is in favour of the last theory, namely, that
of the intermediate or North American-Asiatic source of
this fauna. Still he believes that the actual origin of this
modernised fauna will not be determined until Kocene fossil
mammal beds in the northern portions of America and Asia
shall have been discovered. Such beds have not yet been met
with, nor is there any reason to suppose that they will be.
Have we any geological evidence for the supposition that
there actually existed any such large and intimately connected
northern land-mass at this stage of the geological history of
the earth as Professor Osborn + implies ? No doubt it is
‘generally assumed that Alaska and north-eastern Asia were
joined by land in Eocene times, and Professor Schuchert,t

* Matthew, W. D., “ Osteology of Paramys,” pp. 64—69.
+ Osborn, H. F., “Cenozoic Mammal Horizons,” pp. 35—36.
t Schuchert, C., ‘“‘ Paleogeography of North America,” Plan 96.

ee tian "

——— i le

EARLY TERTIARY MAMMALS 299

in his palaeontological maps, unites America in this manner
with Asia, and by way of Greenland with Europe. But Pro-
fessor Suess contends that, although these affinities in the
Kocene faunas of America and Europe imply united conti-
nents in the north, this land connection was probably not in
the vicinity of Bering Sea. On the contrary, he rather favours
a more direct land bridge between North America and
Europe.*

During the latter stages of the Eocene Period, while the
Wind River, Bridger and Uinta beds were being laid down,
the descendants of the archaic and of the modernised
mammals gradually evolved, and we may suppose that the
archaic mammals finally succumbed in the struggle for exis-
tence. At any rate, they slowly disappeared, and during
the process of their elimination, the fauna of America assumed
a more independent aspect, the affinities with Hurope becom-
ing less pronounced. This need not necessarily imply a cessa-
tion of the intimate geographical relationship between the two
continents. The growth of an impenetrable forest, like that
in the interior of Brazil, the development of local desert
conditions, or the existence of temporary volcanic distur-
bances on the supposed trans-Atlantic land connection, would
have been sufficient to faunistically isolate the two continents
from one another. In the succeeding period, the Oligocene,
the faunal resemblance of western North America and
western EKurope once more became conspicuous. The land
area available for the development of mammalian life cer-
tainly increased in America during early Tertiary times, while
a corresponding decrease may have taken place on the trans-
Atlantic land connection, thus bringing a renewed influx of
strange forms to the New World. Professor Osborn f tells us
that in the White River, John Day and other American Oligo-
cene formations, sixteen new families of mammals made their
appearance, most of them still existing, and that a very
similar modernisation occurred in western Europe. Six new
families appear, apparently simultaneously, in both areas. It
is worthy of note that the opossum family (Didelphyidae) and
the rhinoceroses (Rhinocerotidae) now make their first entry

* Suess, E., “ Antlitz der Erde,” Vol. ITI.2, pp. 764—765.
t Osborn, H. F., ‘‘ Cenozoic Mammal Horizons,” pp. 58—-59.

230 ORIGIN OF LIFE IN AMERICA

into North America, while the monkeys (Primates) disappear
for ever from the continent.

In his restoration of Oligocene conditions in North
America, Professor Schuchert still depicts North America
as being joined in the far north by wide land bridges with
Asia and Kurope, while practically submerging the whole of
the West Indies. As we shall learn later on, an intimate
relationship exists between the shallow water marine forms
of early Tertiary Kuropean and Antillean deposits, and this
has given rise to the suggestion that a land bridge must then
have united Europe and the Antilles. If ‘my view should be
substantiated, that the resemblance in the Oligocene faunas of
Kurope and south-western North America is due to the exis-
tence in Oligocene times of a mid-Atlantic land bridge, the
West Indian area, of course, could not have been submerged
at that time.

After a short phase of independent svoluiian, during which
the Oligocene deposits of western North America insensibly
pass into Miocene ones, the succeeding Middle Miocene beds
are characterised by the appearance of a large number of new
forms, among which the elephants (Proboscidea) deserve
special mention. Some of these new immigrants are, ap-
parently, of African, others of Eurasiatic origin. The
Miocene beds of Europe and of America are remarkable for
the similarity of their fauna. The conclusion deduced from
this fact by Professor Osborn * is that the North American
middle Miocene formations contain animals which first appear
in the lower Miocene of Europe, just as the American lower
Miocene contains animals that first appear in the upper
Oligocene of Europe.

Now it is quite possible that while the faunistic inter-
change between western EKurope and western North America

took place by means of one land connection during early

Tertiary times, this land bridge was replaced later on by an
entirely different one. Professor Depéret + had some such
idea in his mind in expressing the view that the Miocene and
Pliocene migrations from Europe to America probably
arrived by way of Asia and the Bering Strait, while the earlier

* Osborn, H. F., “ Cenozoic Mammal Horizons,” p. 76.
+ Depéret, C., “Transformations of the Animal World,” p. 314. —

CONCLUSIONS 231

ones came direct from Europe. Professor Suess,* on the
other hand, favours a north Atlantic land connection in high
latitudes between Greenland, Iceland and Scotland, and he
thinks its origin dates back to the beginning of the Miocene
period. Considering that there is such unanimity in favour
of some kind of land bridge between the Old World and the
New at this time, it is strange that Professor Schuchert
should entirely isolate North America in his palaeogeographi-
cal maps from the Old World, not only in Miocene, but even
in Pliocene times.

Although the Pliocene fauna, according to Professor
Osborn (p. 81), is as yet only imperfectly and sparsely
known, being characterised by hosts of southern invaders
which now flood the continent, a direct land bridge between
North America and the Eurasiatic continent must likewise
have existed, unless we assume that the mighty elephant
Tetrabelodon (Dibelodon) which is represented by several
species in the New World, reached North America by way
of South America. Whether the still existing more hardy
f stock of Asiatic immigrants came to North America towards
i the end of Pliocene, as I argued in a previous chapter
(p. 97), or during Pleistocene times, is a question which had
not hitherto, I think, been seriously debated. That their pre-
sence in North America is due to a wide land bridge across
Bering Strait (see Fig. 7) seems to me evident.

In this very brief survey of the past faunas of North
America I have endeavoured to show that an important centre
of evolution and dispersal existed in western North America
in the past, just as it exists to a lesser degree at the present
day. ‘The strong faunistic affinity between western North
America and western Europe, which we can still trace at this
| moment among many of the invertebrates and lower verte-

brates of the two areas, seems to be the outcome of an ancient
direct geographical communion between these land-masses.
| Certain features in mammalian palaeontology appear to

strengthen my views, which are primarily based on a study
of the modern fauna. In the succeeding chapters I shall
bring forward further evidence showing that North America

| * Suess, E., “ Antlitz der Erde,” Vol. ITT.2, p. 765.
| . t Schuchert, C., “ Paleogeography,”’ Pl. 98—100.
|

}

932 ORIGIN OF LIFE IN AMERICA

and Europe were joined in the south, while northern, Asia was
in all likelihood disconnected from the former. The principal
point which I think has been clearly demonstrated is that the
south-western centre of dispersal has exerted a powerful in-
fluence on the development of the living fauna of North
America. There still remains one other feature that I wish
to allude to before concluding this chapter.

I have mentioned above that, while eastern Mexico was
either wholly or partially submerged by the sea during later
Mesozoic and early Tertiary times, most of western Mexico
and a portion of the Californian coast remained dry land, as
far as we know, all through geological history. It ought on
that account to be a preservation ground for all kinds of
relicts of bygone ages. And so it is. I have cited a number
of them already, although the country can scarcely be con-
sidered as being exhaustively explored. The fresh-water
fishes more than any other group show what zoological riches
may still be discovered there. The Lerma river system, for
example, in south-western Mexico has a fish fauna, accord-
ing to Dr. Meek,* which is quite as distinct and character-
istic as if it were on an island in the sea. Of the forty-nine
species of fishes now known to occur in this area, nota single
one is found elsewhere. These forty-nine species belong to
seventeen genera, ten of them being quite peculiar to this
region. This result is all the more surprising, as it has often
been argued, by advocates of accidental introduction, that the
eggs of fishes are apt to adhere to the legs or feathers of water
birds, being thus easily transported to other river systems
or isolated lakes. The extremely distinct and isolated
character of the Lerma river area implies that dispersal of
fishes is not affected by such agencies of accidental transport.
Fishes only migrate from one river to another when a change
of drainage occurs in the head waters, or when the stream
itself shifts its course.

* Meek, S. E., “ Fishes of Mexico,” pp. 775—784.”

CHAPTER X r .

THE FAUNA OF CENTRAL AMERICA

THE problems presented by a study of the fauna of Central
America are of the utmost significance in our investigations
into the origin of the American fauna as a whole. Even
the casual observer cannot fail to perceive that certain animals
from each of the two great continents lying to the north and
south of Central America, tend to spread along the narrow
isthmus, and thus intermingle with one another. When we
look at Dr. Wallace’s map of what he calls the ‘‘ Neotropical
Region,”’ and notice how the South American fauna has
apparently invaded the whole of Central America, and even
erept northward along the lowlands of Mexico, so that the
triangular table-land of that country, with its northern in-
habitants, looks as if it had been forced like a wedge between
the two wings of the southern army of invaders, the whole
history of events seems to be clearly unfolded before our eyes.
Apparently, quite a simple zoogeographical problem, and one
that is easily soluble by a study of the distribution of existing
animals. Thus it seemed to Dr. Wallace. Of the geology of
Central America nothing was known when he wrote his
famous work on the distribution of animals. Nevertheless,
he argues (pp. 10—13), from the sudden appearance in post-
Tertiary times of numerous South American forms of
edentates in temperate North America, and from such facts
as the occurrence of some identical species of sea fish on the
two sides of the Central American isthmus, that the union
of North and South America must be a comparatively
recent event, and that these continents must have been sepa-
rated during Miocene and Pliocene times by a wide arm of the
sea. When the evidence of both land and sea animals support
each other as they do here, adds Dr. Wallace,* the conclusions

* Wallace, A. R., “ Distribution of Animals,” Vol. IT., pp. 57—59.

234 ORIGIN OF LIFE IN AMERICA

arrived at are almost as sure as if we had geological proof
of these successive subsidences. The author of the ‘‘Geo-
graphical Distribution of Animals ’’ thus not only claims that
zoogeography is of great value as an interpreter of geological
phenomena, but he feels confident of having indicated the
correct solution to the problem of the faunistic relationship
between the two continents. There are one or two points,
however, in the fauna of South and Central America, which
seem to throw doubt on Dr. Wallace’s interpretation of the
facts of distribution. He states (p. 58) that when the final
union of the two continents took place, the tropical climate
of the lower portion of Guatemala and Mexico would have
invited rapid immigration from the south, while some
northern forms would have extended their range into and
beyond the newly elevated territory. That the fauna of South
America has advanced across the isthmus, and has even in-
vaded the State of Texas, appears probable from a study of
the existing fauna. We need not even cite the presence of
the South American fossils in North America in favour of
this view. All sections, indeed, of the fauna seem to have
taken part in this northward advance, even the fishes.

Take for example the members of the family Cichlidae.
Over one hundred and fifty species of this strictly fresh- _
water group are known from America, the great majority
being confined to South America. Mr. Regan * is of opinion
that the Central American and Mexican species are more
specialized than the South American ones, and that the
former have certainly been derived from the latter. No
member of this family of fishes is known from the Mexican
plateau, and only three or four species extend northward
on either side of it, North America being almost devoid
of Cichlidae (see Fig. 12). All the available evidence
thus points to South America as the place of origin of the
family, as far as the New World is concerned ; and thence it
has spread northward, like hosts of other groups of animals.
This advance must, of course, have taken place as soon as a
connected land passage with suitable lakes and rivers enabled
them to proceed northward. Dr. Wallace thinks that the
sudden appearance of the large South American edentates

* Regan, CO. Tate, “ Fishes of Central America,” pp. xiii—xvi.

Fi@. 12.—Map of the World,

veer = a,
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Tee “XC
BERR Pen
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FISHES OF CENTRAL AMERICA 235

in North America occurred in post-Tertiary times, for he
believes Central America to have been still submerged during
the Pliocene Period. The term “ post-Tertiary,’’ I may men-
tion, is synonymous with Quaternary or post-Pliocene. Any
geological deposits more recent than Pliocene come within
the meaning of that term. But the skeletons of the great
South American Mylodon and Megalonyx certainly occur in
Texas in true Pliocene beds. I do not think there is any geo-
logist in America now who would uphold the Pleistocene, or
even less the post-Glacial age of these deposits. My conten-
tion, therefore, is that the northward advance from South
America is a pre-Glacial or pre-Pleistocene event.

Now one of the most remarkable and astonishing features
of that faunistically so peculiar continent of South America
is that, whereas its tropical fauna has very little affinity
with the fauna of North America, the more remotely placed
Chilean and Patagonian faunas present in some groups of
animals a striking resemblance to it. This character will be
more fully dealt with in another chapter (pp. 410—419). It
may be mentioned, however, that numerous groups, and even
species, of northern plants are met with in Chile, which are
wholly, or almost entirely, absent in the intervening -region,
occupying an area of thousands of miles. Northern genera of
butterflies and beetles, such as Argynnis, Colias and Carabus,
all of which are almost unknown in the countries immediately
south of Mexico, reappear in numbers in the extreme southern
tip of South America, Dr. Wallace thought that this south-
ward migration of northern forms of animal life must have
been effected mainly during successive Glacial epochs, when
the mountain-range of the isthmus of Panama, if moderately
increased in height, might have become adapted for the
passage of northern forms, while storms might often have
carried insects from peak to peak, over intervening forest
lowlands, or narrow straits of sea. Dr. Wallace’s idea that the
A mountains all along Central America were formerly higher
4 than they are now and sustained northern forms of animal
. life is not supported by any evidence. Considering that he
imagined the long isthmus to have been slowly rising from the
_ sea since pre-Glacial times, Dr. Wallace’s suggestion that
t the mountains were so much higher during the Glacial Kpoch

236 ORIGIN OF LIFE IN AMERICA

than they are now, hardly seems well founded. Another still
stronger objection to Dr. Wallace’s* theory is that the
northern forms alluded to as occurring in Chile and Patagonia
belong almost all to different species, sometimes even to dif:
. ferent genera, from their northern relations. If storms had
anything to do with this distribution they could only have
acted during very long intervals of time so as to produce such
specific and generic differences. Moreover, how could winds
or storms affect the distribution of Carabus, which is a flight-
less ground insect living under: stones ? How could these
agencies have transported fresh-water species across the im-
mense tropical area, for several Chilean fresh-water forms
exhibit a similar northern affinity ? These are some of the
problems that present themselves to us. There are numbers
of others. Why should the family of tortoises, Dermate-
mydidae, which is known to have inhabited the North
American continent since Cretaceous times, have become ex-
tinct there and be now confined to Central America ?

The searcity of land and fresh-water fossils in Central
America obliges us to resort to zoogeography and to the meagre
geological information we possess in elucidating these and
other problems. Before dealing with the general faunistic
features of Central America, a few remarks on some of the
more important geological characters will be of interest.

The long neck of Central America from the isthmus of
Tehuantepec to Panama, which joins North and South
America to one another, has a length of about one thousand
five hundred miles. We are sometimes apt to forget that it
does not lie in a north and ‘south direction, but almost east and
west. Nearer South America the neck of land starts in a
due westerly direction and only gradually turns somewhat
towards the north and finally north-westward. Very little of
this immense stretch of land has as yet been geologically sur-
veyed. Nevertheless, some valuable hints as to its geological
history have been gathered. In his essay on the geology of
the isthmus of Panama, Professor Hill f ‘tells us that, pos-
sibly before the vast accumulations of more modern igneous
and sedimentary rocks of Tertiary and post-Tertiary age were

* Wallace, A. R., ‘‘ Distribution of Animals,” Vol. IT., p. 43.
+ Hill, R. T., ‘Geological History of Panama,” pp. 241—257.

GEOLOGY OF CENTRAL AMERICA 237

laid down, a foundation of granitic rocks, occurring in an east

and west arrangement, existed on the site of Central America.

Apparently parallel granitoid ridges extended from the longi-
tude of Trinidad directly across the path of the main con-
tinental trends through forty degrees, as far north as Acapulco
in Mexico. These fragmentary data, he says, are sufficient to
indicate that in pre-Tertiary times: there may have been a
basement barrier of granitic rocks forming an east and west
arrangement which outlined the Central American region, and
constituted an ancient buttress against or upon which the
higher mountain folding has originated. Professor Suess,*
too, speaks of the mountain chains of Yucatan and Guate-
mala as the western continuations of the Antillean system,
contending that North and South America are to be looked
upon as two radically distinct continents, separated from one
another by a third element, that of Central America and the
Antilles. All this agrees to some extent, as we shall see later
on, with the conclusions we can draw from a study of zoogeo-
graphy. Central America and the Antilles, which are collec-
tively spoken of sometimes as the remnants of an ancient
“* Antillean Continent,” possess a distinct and peculiar fauna
quite apart from the South American one which has invaded
this area.

Towards the end of the Mesozoic Era parts of this Antillean
continent must have begun to subside. About that time signs
of the coming volcanic activity appeared all along the Central
American region. During the successive igneous eruptions in
early Tertiary times, which have been continued with varied
intensity to the present day, the Atlantic Ocean seems to have
invaded the existing area of Central America and submerged
portions of it. At any rate, Professor Hill} states that
biological and geological evidence led him to the con-
clusion that a shallow marine transgression must have existed
somewhere in Central America during Eocene times, although
there is nothing to show with certainty that the isthmus
of Panama was the exact site of this inter-oceanic. con-
nection. All the same, Professor Schuchert { seems to be

* Suess, E., “ Antlitz der Erde,” Vol. I., p. 700.

+ Hill, R. T., “ Geological History of Panama,” p. 265.
t Schuchert, C., “ Paleogeography of North America,”’ pp. 96—97.

238 ORIGIN OF LIFE IN AMERICA

satisfied that the isthmus of Panama was submerged during
the Eocene Period, and that the submerged area of Central
America greatly increased in Oligocence times. Professor
Hill, who has dealt with various lines of enquiry in regard to
the geological history of Central America, contends that they
all give evidence for the belief that no connection has existed
between the Pacific and Atlantic Oceans since the close of the
Oligocene (p. 270). A very careful re-examination of the
fossils of Gatun, near the Panama Canal, by Professor Toula,
however, throws considerable doubt on the supposed Kocene
age of the deposits containing these fossils. He gives reason
for his belief that they are of upper Miocene, possibly even of
lower Pliocene age, and estimates the depth of water of the
marine channel uniting the two oceans at about a hundred and
fifty feet.*.

In conjunction with Dr. Bése, the same author also in-
vestigated the Tertiary deposits of the isthmus of Tehuantepec
in southern Mexico with very noteworthy results. The fossil
mollusks contained in them indicate that the sea covered the
land to a depth of from fifty to two hundred fathoms, that is to
say from three hundred to one thousand two hundred feet.
As the isthmus does not rise much beyond eight hundred
feet, the existing land, even as far north as this region,
was submerged by a shallow sea. Dr. Bose is inclined to attri-
bute to this fauna an early Miocene age, while Professor
Toula believes it to be younger, in fact distinctly “ jung-
tertidr.”’ +

Now it has been argued, and the argument appears most
reasonable, that we are able to check these results indicating
a submergence of parts of Central America by means of two
other tests, viz., the distribution of living animals and the
palaeontology of North America. The first deals mainly with
the amount of affinity existing between the marine animals |
of the Atlantic and Pacific sides of Central America. From
the nearness or remoteness in relationship of the species on
the two opposite coasts it was thought we might determine at
what particular geological period, if at any, the Atlantic and
the Pacific Oceans were joined to one another across Central

* Toula, F., “ Jungtertiare Fauna von Gatun,” pp. 744—745.

re

+ ‘Bose, E., and F. Toula, “ Fauna von Tehuantepec,” pp. 221 and 273,

ANCIENT CENTRAL AMERICA 239

America. The second test is that of the fossil mammals of
North America. It was pointed out that, as no trace of typi-
cally South American species occur in North American Oligo-
cene or Miocene deposits, the two continents must have been
separated by a sea during the period in which these beds were
laid down. Let us examine these evidences more closely.

A good many writers have discussed the problem of the
former junction of the Pacific and Atlantic Oceans across
Central America, from a purely biological point of view. Pro-
fessor Gregory,* who last summarised the subject, came to the
conclusion that the waterway across Central America was
finally closed in the Lower Miocene, or possibly even in the
Upper Oligocene. Among others he alluded to the researches
of the two Agassiz, father and son, stating that, from a study
of the sea-urchins, they proposed to date the junction of the
two oceans much further back. These zoologists referred the
separation of the two oceans and the formation of the Gulf
Stream, to the period at the close of the Cretaceous, that is to
say, to the end of the Secondary Era. Professor Verrill +
finds that no species of corals are identical on the two sides
of Central America, while even the genera and families show
remarkable contrasts. The numerous genera and families of
reef-building corals, so abundant on the Atlantic side, are
wholly wanting on the Pacific, with the exception of Porites,
which is represented by three or four small species.

Mr. Belt { maintained that the marine mollusks on the two
coasts separated by the narrow isthmus of Darien were almost
entirely distinct. So remarkably distinct are the two faunas,
he says, that most zoologists consider that there has been no
communication in the tropics between the Pacific and Atlantic
Oceans since the close of the Miocene Period. An apparently
rather remote junction of the two oceans is suggested by
all these authors, but none of them express any very strong
convictions on the subject. Dr. Ortmann, on the other hand,
states that the affinities of the Decapod fauna of the Atlantic
and Pacific are unmistakable, and that we have ample and con-
vincing evidence of a former connection between these oceans.

* Gregory, J. W., “ Palaeontology of the West Indies,” pp. 304—305.

+ Verrill, A. E., “ Comparison of Coral Faunae,” p, 500.
{ Belt, Th., “ Naturalist in Nicaragua,” p. 264,

240 ORIGIN OF LIFE IN AMERICA

Seven species of crabs and their allies are identical to the two
oceans, while many others are closely related. The fauna as a
whole implies that the union of the seas cannot have been of
a very recent date. Accordingly Dr. Ortmann * is of opinion
that there was no communication since Miocene times.

In 1880 Dr. Giinther + declared that the genera of fishes,
with scarcely any exception, are identical on the two sides
of Central America. Of the species found on the Pacific side,
nearly one half, he states, have proved to be the same as those
of the Atlantic, and he upholds the view of the existence of
straits and channels between the two seas ‘until a geologically
recent period. Since Dr. Giinther expressed these views, the
fish fauna of this region has received renewed attention and
study, over a thousand species now being known from the
coasts of the two seas. Of this large number only seventy-
one species, or six per cent., are common to the two oceans,
according to the latest researches of Professor Jordan. This
great discrepancy between Dr. Ginther’s and Professor
Jordan’s results arises, of course, to a large extent from the
different views these observers hold as to specific limits.
To account for the remarkable identity of genera and the
divergence of species, Professor Jordan { suggests that the
isthmus of Panama was depressed in or before Miocene times,
that the channel was shallow, and that the currents set chiefly
westward, thus favouring the transfer of Atlantic rather than
Pacific types. In the case of the Medusae, the affinity between
the littoral faunas of the two sides of Central America is
much closer according to Dr. Bigelow§ than in the higher groups.

It has been suggested by Messrs. Gill and Bransford || that
the occurrence of marine fishes in the great lake of Nicaragua
is to be looked upon as an indication that the sea once flooded
the area now occupied by these lakes. That these fishes are
true “relicts ” of the past, representing the survivors of a
marine fauna, has recently been reaffirmed by Dr. Meek.[

* Ortmann, A. E., ‘‘ Distribution of Decapods,” p. 398.

+ Gunther, A., “ Study of Fishes,” p. 280.

{ Jordan, D. 8., “Study of Fishes,” Vol. I., pp. 272—280.

§ Bigelow, H. B., ‘“Medusae,” p. 228.

|| Gill, Th., and J. F. Bransford, “ Fishes of Lake Nicaragua,” p. 179.
q Meek, S. E., “ Fishes of Nicaragua,” p. 99,

AGE OF CENTRAL AMERICA 241

The species in question are, in the first instance, two sharks,
viz., Carcharhinus nicaraguensis and Pristis antiquorum, as
well as Pomadasis grandis and others whose ancestors are
marine forms. The antiquity of the region is indicated by
the occurrence both in Lake Nicaragua and Lake Managua
of the Central American gar-pike (Lepidosteus tropicus).

The studies of geographical distribution, particularly those
of marine species, have thus led to the conclusion that the
Central American land bridge has been in existence certainly
since pre-Glacial times. No zoologist has suggested even the
possibility of a submergence of Central America having taken
place as late as the Pleistocene Period. No biological support
can be given, therefore, to the theory which has been advanced
by some writers, that the Glacial Period was due to a diversion
of the Gulf Stream across the isthmus of Panama. On the
other hand, Central America was certainly submerged by a
shallow sea in two or more places in early Pliocene or Miocene
times. Another very important character, which is revealed
both from a study of the recent and fossil marine fauna, is the
Atlantic facies of the animals. The movement of the species
seems to have taken place from the West Indian area towards
the Pacific Ocean, thus implying the existence of a strong
current in that direction. Speaking of the Tertiary deposits
of Tehuantepec, Dr. Bose * remarks that the main mass of the
species contained therein are related to Atlantic forms. Only
very few show affinities with Pacific types. Similar views
were expressed by Professor Jordan and Dr. Ortmann in
regard to the recent marine fauna.

A further complication, as Professor Gregory.+ pointed
out, remains to be considered. It is not at all certain, he
thinks, that when the Isthmus of Panama was submerged
there was free communication between the Atlantic and the
Pacific Oceans. The Caribbean Sea, he argues, may then have
been a gulf of the Pacific, separated from the Atlantic by the
land area of the hypothetical ‘‘ Antillia.”” As I shall show in
the next chapter, which deals with the origin of the West
Indian fauna, the Caribbean Sea could not have been' separated
from the Atlantic Ocean at so late a geological period as that

* Bose, E., and F. Toula, ‘‘ Fauna von Tehuantepec,”’ p. 220.
+t Gregory, J. W., Palaeontology of the West Indies,” p. 305.
L.A. R

242 ORIGIN OF LIFE IN AMERICA

during which the sea spread across Central America. The
general opinion seems to be that the submergence-of Central
America was due to extensive subsidence in the Caribbean
area and likewise in the Gulf of Mexico. The Mediterranean
character of the West Indian marine fauna, moreover, implies
the probability of a free migration from the one area to the
other along some ancient shore-line. A land bridge joining
North and South America along the chain of the Lesser
Antilles, alluded to by Professor Gregory, may possibly have
existed; but it must, I think, already have been destroyed
at the time of the submergence of the Isthmus of Panama.
And yet I concur with Professor Gregory in thinking that
when the latter was submerged there need not necessarily
have been free communication between the Atlantic and the
Pacific Oceans. We must remember. that all efforts have
hitherto failed to discover any traces of Tertiary sediments on
the sea-board between southern Mexico and Panama. This
seems to imply that land lay to the west of Central America, -
and that the Pacific Ocean was formerly situated further
westward than at present. What would appear as connections
between the two oceans may have been merely shallow bays in
the land referred to. Certain peninsulas would then have
projected eastward from this old Pacific land towards those
parts of Central America that were then in existence (see
Fig. 16). Without giving further evidence, these theories
may appear somewhat visionary, but as the subject will be
more fully discussed later on (p. 408), I need not enlarge
upon it at present.

A comparison of the marine faunas of the two shores of
Central America does not yield such satisfactory results in
establishing the geological age of the submergence, because
we have as yet little idea of the length of time during which’
animals may retain their specific characters. The evidence
derived from the first appearance in North America of dis-
tinctly South American mammals would seem to give us a
better clue as to the date of the formation of the present
Central American land bridge.

This appeal to the past dispersals of mammals in recon-
structing former conditions of land and water has been utilised
in several of the previous chapters, and in this case many bio-

— ee pe i

HISTORY OF THE MARINE FAUNA 243

logists have attested their strong belief in the validity of the
argument. A very early Tertiary or late Mesozoic influx of
mammals from South America into North America has already
been alluded to. After this event long periods of time elapsed,
during which the two continents were seemingly separated
from one another. Then southern mammals once more
appeared in the north. This later invasion is proved from
the contents of the deposits in Texas. Here we meet
with gravigrade edentates, and these deposits have now
been definitely placed by Professor Osborn * to the middle
Pliocene. Hence Central America in its present form and
shape would be of Pliocene origin. Although Mr. Lydekker +
places this event at the end of the Miocene Period, Professor
Depéret { and Dr. Smith Woodward § concur in the opinion
expressed by Professor Osborn which is in conformity with
that elicited by Professor Toula. The latter bases his evidence
on the fossils contained in the Panama and Tehuantepec
deposits.

Since the testimony derived from the recent marine fauna
also agrees fairly well with the above conclusions, it seems
reasonable to conclude that Central America in its present
outlines, forming a highway for intercommunication between
North and South America, came into existence about the
beginning of the Pliocene Period. Thus one of the problems
alluded to at the beginning of the chapter is apparently
solved.

Yet still another difficulty has suddenly arisen owing to
the recent most surprising discovery of true edentate re-
mains of Megalonyx type in the Mascall beds of Oregon,
which are of Middle or Lower Miocene age.|| If the
Gatun deposits near Panama are really, as Professor Toula
affirms, of Upper Miocene age, how can we reconcile the
submergence of Panama, and probably also of the isthmus of
Tehuantepec, with this latest discovery in Oregon ? The whole
problem is evidently much more complex than it at first ap-

* Osborn, H. F., ‘“ Cenozoic Mammal Horizons,” p. 82.

1 Lydekker, R., “ History of Mammals,” p. 119.

} Depéret, O., “Transformations of Animal World,” p. 282. -
§ Woodward, A. Smith, “ Palaeontology,” p. 429.

|| Osborn, H. F., “ Age of Mammals,” p. 289.

R 2

244 ORIGIN OF LIFE IN AMERICA

peared. In the Oligocene deposits of the northern continent,
as above mentioned, there are no distinctly South American
_ species. Yet, curiously enough, when we come to still earlier
strata, we again meet with remains of animals that exhibit
characteristically South American features. In the Puerco
formation, in north-western New Mexico, a number of
peculiar mammalian bones have been discovered, which were
referred by Professor. Cope to the extinct order Tillodontia,
whereas Dr. Wortman endeavoured to show that Cope’s
genera Psittacotherium, Onychodectes and Conoryctes were
ancestral to the Gravigrada or ground sloths of South America.
Dr. Wortman* proposed that they be placed in a new sub-
order of the edentates, which he named Ganodonta. But he
did not look upon these animals as immigrants from South
America. He thought this order of primitive mammals must
have actually arisen in North America, and have thence emi-
grated to South America before the close of the Eocene
Period. Although these Ganodonta are no longer considered
as ancestral to the ground sloths, the same Puerco formation
has yielded other mammals which show distinctly South
American or rather Patagonian affinities. Dr. Wortman’s
theory as to the North American origin of the Ganodonta
has not found favour. Dr. Osborn, in fact, urges that a
direct land connection with South America is indicated at
this stage of geological history in order to account for the
South American features in the North American fauna. This
view has been amply confirmed by the remarkable discovery in
Wyoming, in a deposit of Middle EHocene age (Bridger), of
the remains of a true armadillo closely related to the modern
armadillos, but exhibiting a few more primitive characters.f
Since Dr. Ameghino’s researches in Patagonia have brought
to light such a wealth of edentates from the earliest
Tertiary, and probably even from Mesozoic deposits, scarcely
anyone can doubt that South America is the original home

of that group of mammals, and that they have passed from

there during the Eocene Period and earlier into North
America, and not vice versa, as Dr. Wortman suggested. —
But very few would assert that the physical geography of the

* Wortman, J. L., “ Psittacotherium,” pp. 259—262.
+ Osborn, H. F., “An Armadillo from the Eocene,” p. 163.

AFFINITIES. OF NORTH AND SOUTH 245

New World was the same then as it is now, and that Central
and South America had already been evolved in anything like
the present outlines. As I shall endeavour to demonstrate
later on, South America did not then exist as a distinct great
continent. A large land-mass ‘evidently lay in the neigh-
bourhood of the existing State of Brazil and another further
south. And as far as we know, the southern land-mass was
the original home of the edentates. Between it and Central
America on the site of the present South American continent
there were one or more broad marine channels, or oceans, as
we might call them. And yet the edentates succeeded in
attaining North America. I do not now wish to discuss my
reasons for the supposition that western Mexico was then
united by a direct land bridge with Chile. I only mention it
in order to indicate that the appearance of edentates in the
Eocene of North America does not afford a proof of the ex-
istence of Central America at that time, nor during the
Miocene Period.

Professor Osborn, as I mentioned before, indicates the
nature of the land connection between North and South
America in the dawn of the Tertiary Era on a map which he
kindly allowed me to copy (Fig. 21). However, he expresses
the belief that already in early EHocene times, that is to say
almost before the appearance of the above-mentioned arma-
dillo in North America, the land bridge had ceased to exist.
We are too apt, I think, to look upon South America as exclu-
sively the home of edentates, forgetting that many other mam-
mals may have originated there too. We may not all agree
with Dr. Ameghino* in attaching the importance he does
to that continent as a source of the Tertiary mammalia,
but I believe we possess other evidences of a faunistic inter-
change between Chile and Patagonia on the one hand, and
western North America on the other, during the ages that
passed between the Lower Kocene and the Miocene.

In southern Africa we meet with a group of small blind
subterranean creatures, the golden moles (Chrysochloridae)
which are among the most primitive mammals in existence.

They are quite confined at present to South Africa. But

* Ameghino, Fl. “ South America, the Source of Mammalia,”’

.

246 ORIGIN OF LIFE IN AMERICA

within recent years the remains of a small insectivore have
heen met with in the early Tertiary Santa Cruz deposits of
Patagonia. This mammal, according to Professor Scott,* is
genetically related to the African golden moles. The South
American Necrolestes, as it has been called, is certainly more
primitive in structure than its African relations. Moreover,
in western North America fossil mammals have been dis-
covered both in Oligocene and Miocene strata which have been
referred to the same family Chrysochloridae. It is true that
Dr. Matthew + is now inclined to place the Oligocene Apter-
nodus among the nearly related family Centetidae, but the two
other genera Xenotherium and Arctoryctes are still looked
upon as true chrysochlorids. A possible land connection
between Africa and South America will be discussed later on.
Whether Patagonia was the original home of the chryso-
chlorids or South Africa we cannot tell, but the family may
possibly have spread from South America to North America
by utilising the hypothetical land bridge that I think lay to
the west of the present continent.

A few words of appreciation of the splendid work that has
been done in making us acquainted with the rich fauna and
flora of Central America are due to Mr. Godman. For years
he and Mr. Salvin laboured with great industry and at con-
siderable expense in bringing together an immense collection
of vertebrates and invertebrates, subsequently publishing the
series of beautifully illustrated volumes of the “ Biologia
Centrali-Americana ”’ in which the results of their studies were
made known to the scientific world. In the volume describing
the botany of Mexico and Central America there is an excel-
lent summary dealing with the constituents of the flora and
their relationships. No such summary has been attempted in
the other volumes, so that Mr. Hemsley’s account of the plants
of Mexico and Central America is of particular value to those
who are engaged in a study of the zoogeography of that region.

The first item of interest is one which we have noticed
occasionally among apparently very ancient groups of North
American animals. Genera like the amphibians Spelerpes
and Amblystoma, which have their headquarters in Mexico,

* Scott, W. B., “ Report of Princeton Expedition,” Vol. V.
+ Matthew, W. D., “The Skull of Apternodus,” p. 35,

— ae oe ee > -

FLORA OF CENTRAL AMERICA 247

are either absent or very rare in the western United States of
North America, while abundant in the eastern States. Some
of these bear an impress of their antiquity in their wide and
discontinuous range. Now Mr. Hemsley enumerates the fol-
lowing genera of trees as occurring in southern Mexico and in
the Atlantic States of North America, though they are absent
from the Pacific forests of the western United States:
Magnolia, Asimina, Tilia, Robinia, Liquidambar, Ilex, Dio-
spyros, Bumelia, Ulmus, Celtis, Morus, Ostrya, Carpinus and
Carya. Even species of plants from southern Mexico and the
Atlantic States of North America are sometimes identical,
such as Liquidambar styraciflua, Ostrya virginica and Car-
pinus americana. And yet only four out of the fourteen
genera referred to extend even to northern Mexico. Of some
of these we possess fossil evidence that they lived in Kurope
already in early Tertiary times, and we may safely assume that
the whole group is of great antiquity. The flora of Guatemala
is essentially. of the same composition, according to Mr.
Hemsley, as that of southern Mexico, though apparently less
rich in specific diversity. Some of the trees just alluded
to, such as limes (Tilia) and elms (Ulmus), are unknown
in Guatemala; others, for instance sweet gums. (Liqui-
dambar), mulberries (Morus), lever-wood (Ostrya) and horn-
beams (Carpinus), occur in that country. -The southern floral
province of Mr. Hemsley comprises Nicaragua, Costa Rica
and Panama; and, as might be expected, these countries ex-
hibit a much closer relationship with the South American
tropical flora than. Guatemala or Mexico do. The endemic
generic element of the whole of Mexico and Central America
is rather inconspicuous, but the southern floral province is by
far the poorest of the three into which the region has been
divided. One of the most curious features in the constitution
of the flora of Mexico is one which I have already briefly.
referred to, namely, the presence there and in the extreme
south of South America of certain northern genera of plants
which are absent or only represented in a few scattered dis-
tricts in the intermediate region. Mr. Hemsley assumes that
such plants have spread southward in remote times. There
are likewise genera of distinctly southern origin with.a simi-
larly discontinuous range in a northward direction. I need

248 ORIGIN OF LIFE IN AMERICA

only mention Fuchsia, which is abundant in Chile and Pata-
gonia, reappears more sparingly in Colombia, and is almost
unknown further north until we come to Guatemala and
Mexico. The extreme antiquity of this genus is indicated
by its occurrence on the island of Haiti (F. triphylla), while
it is altogether absent from the rest of the West Indian
Islands.

In his analysis of the flora of the whole region, Mr.
Hemsley * informs us that the northern province, that is
to say the plateau of Mexico, is the focus of a xerophilous
flora extending into the dry regions of south Mexico and into
the territories north of Mexico. The central province, com-
prising southern Mexico and Guatemala, possesses a mingling
of northern and southern types exhibiting an extraordinarily
rich production of local species. The southern province is
merely an outlier of the American tropical flora. The tropical
element of the whole flora is more closely allied to that of
eastern South America than to that of the West Indies.

The relationship of the Mexican and Central American
floras to those of other parts of the world is also of import-
ance. Thus Mexico and Central America have a large number
of genera in common with eastern Asia, with Africa, Mada-
gascar and Europe. They likewise exhibit affinities with the
Galapagos islands, with New Zealand, Australia and Polynesia.

Now, if we compare the results of the study of botany with
those derived from an examination of the mammalian fauna,
we are struck at once by the fact that the plants among which
the mammals live must be of much greater antiquity than the
latter. As Mr. Alston? tells us, the mammals of Mexico
and Central America are composed, partly of southern species
not found southward of Mexico, of a few that extend as far
south as Panama, and chiefly of South American ones which
have spread across Central America. There are also a number
of autochthonous species in this region. Yet very few of the
genera are found in other parts of the world than America.

Among our new acquaintances we meet for the first time
with the kinkajous, one species of which (Potos flavus) has
succeeded in reaching the State of Vera Cruz in Mexico.

* Hemsley, W. B., “ Botany of Central America,” pp. 306—315.
t Alston, E. R., “ Mammals of Central America.”

ee ee ee ee

MONKEYS AND RACCOONS 949

From my previous remarks (p. 152) it would appear as if the
raccoon family (Procyonidae) had originated in some western
land in America, and yet the genus Cercoleptes (Potos), which
belongs to this family, is certainly an invader from the south.
Indeed, when we examine the range of the members of this
typically American family of Procyonidae, we notice the
peculiar feature that almost all the species are confined to the
Pacific coast. The raccoon (Procyon lotor) no doubt has ex-
tended its range to the eastern States, while the allied species
Procyon maynardi, as we have learnt, is even confined to the
Bahama islands, and one, the coati (Nasua rufa), has a wide
distribution in South America from Bolivia eastward. Almost
all the other members of the family, however, inhabit
curiously disconnected areas in the vicinity of the Pacific
Ocean. Bassaricyon lives in Ecuador, Panama and Costa
Rica. One species of Bassariscus is peculiar to the island
of Espiritu-Santo near lower California, another ranges from
Mexico to the western States, a third occurs in western
Mexico, Guatemala, Costa Rica and on Mount Chiriqui, in
western Panama, at a height of 6,000 feet. Of the coatis
(Nasua), one species passes from Mexico northward to Cali-
fornia and southward to Costa Rica, another is confined to
the island of Cozumel, a third lives in the Kcuador mountains
at a height of 7,000 feet, whereas Nasua olivacea is met
with in Santa Fé de Bogota and in the Merida of Venezuela
at heights up to 12,000 feet. Altogether it looks as if the
members of the family Procyonidae had spread from various
western foci. Some of them may have retained their original
distribution, while the more adaptable genera sent outposts
eastward into the great continents. The early stages of this
evolution must have taken place before either Central America
or South America had become consolidated into anything like
their present shapes. Later on I shall have occasion to dis-
cuss other similar cases of discontinuous distribution occur-
ring among the lower vertebrates. All of these appear to be
due to the same peculiar features in the physical geography
of Tertiary America.

In eastern Mexico we make our first acquaintance with
monkeys. In early Eocene times, as already mentioned,
monkeys, belonging to extinct groups, probably entered the

.

250 ORIGIN OF LIFE IN AMERICA

United States from the south. They seem to have had a short
existence in North America, for no trace of them has been
noticed in later deposits. Ever since renewed facilities for a
northward advance occurred an entirely new invasion has
taken place, and one of the “ howlers ” can now be heard at
night even in the forests of Vera Cruz in eastern Mexico. A
spider monkey (Ateles vellerosus) may be seen in the same dis-
trict gracefully swinging from branch to branch. These
monkeys differ in distribution from the raccoon family in so
far as they have their centre of distribution in Brazil and
northern South America, from which they no doubt invaded
Central America in more recent geological times. There are
other families of mammals which we meet here for the first
time. We need not dwell on them any longer, as we shall
have occasion to become acquainted with them in subsequent
chapters.

The wealth of new bird life in Central America is very
striking, and is vividly described in Mr. Belt’s * delightful
book of travels in Nicaragua. Among the more noteworthy
families are the toucans(Rhamphastidae) ,with their enormous
gaily-coloured bills, the humming-birds (Trochilidae), a great
-variety of parrots, the peculiar curassows and many others.
Some of these of course, like the humming-birds, enter the
United States largely during their northward migrations, and
to some extent are resident in the southern States. I should
also mention the most beautiful of all birds, the quesal
(Trogon resplendens), or royal bird of the Aztecs as it has
been called, with its delicately tinted plumage of metallic
green and blue, and its long waving plumes. The Trogonidae
now have their headquarters in Central and South America,
but Trogon gallicus occurs in France in Miocene deposits ;
and this seems to suggest in what manner the early members
of the family crossed over to Africa and the Oriental Region,
where some genera are still found living; the discontinuous
range corroborating the palaeontological evidence of the great
antiquity of the group. As Messrs. Salvin and Godman +
remind us, the avifauna of Central America is essentially

* Belt, J., “ Naturalist in Nicaragua.”
+ Salvin, O., and F. D. Godman, “Birds of Mexico and Central

America,” .

— a A oe get te,
Sas - po shee
: .

BIRDS OF CENTRAL AMERICA 251

neotropical, with certain peculiar endemic forms, the greater

number among the latter being confined to Mexico and
Guatemala. | |

I alluded above to the fact that the family of tortoises,
Dermatemydidae, is entirely confined to Central America.
The only species of the family (Dermatemys mawi) inhabits
precisely that part of Central America which we have reason
to believe to be one of its oldest parts, viz., Guatemala and the
neighbouring Honduras and Yucatan. Several members of
the family formerly lived in North America. They first ap-
peared in Cretaceous times, and still inhabited the south-
western States during the Hocene Period. It is possible they
may then have spread to Guatemala, becoming subsequently
extinct in their centre of dispersal.* Another family which
I mentioned before (p. 134), the ‘ snapping turtles ’’ (Cheli-
dridae), occur in eastern North America from Mexico to
Canada. Southward of their range they are found only in
Guatemala and Ecuador. We have noted examples of a
similar discontinuous range before. Others will be cited in
the next chapter. :

More important from a faunistic point of view are such
creatures, as for instance the snake-like limbless amphibians,
belonging to the family Coeciliidae. They live in moist ground,
and lead altogether a burrowing life. Their distribution ought
to give us, therefore, some valuable hints as to former changes
of land and water. Dr. Sarasin + looks upon this family as a
pre-Cretaceous relict, on account of its peculiar discontinuous
range, namely India, the Seychelles, east Africa, west Africa,
South and Central America. Whether we agree with him or
with Dr. Alcock,{ who believes that the family wandered
along a continuous land surface from India across Africa to
northern South America in early Tertiary times, there can be
no doubt at all as to these subterranean amphibians being
exceedingly ancient. The American home of this circum-
tropical family, as Dr. Gadow § points out, is South America.
No members are known from the West Indies or the Galapagos

* Hay, O. P., “ On Fossil Turtles,” p. 32.

+ Sarasin, F., ‘‘ Geschichte d. Tierwelt von Ceylon,”’ pp. 14—16:

t Alcock, A., "« a Decieare of Apodous Amphibian,” p. 270.

§ Gadow, H., ‘‘ Distribution of Mexican Amphibians,” pp. 199—200.

252 ORIGIN OF LIFE IN AMERICA

islands. Dr. Gadow next proceeds to argue that because one
of these coecilians inhabits eastern Mexico, its ancestors must
have travelled slowly across the whole neck of Central America
since the close of the Miocene Epoch, when he assumes the
isthmus to have been first opened up for southern immigrants.
This argument is in so far faulty, as the coecilians need not
necessarily have passed through Central America. The inti-
mate relationship that exists among many ancient species of
Central America to those of northern South America suggests
the existence of some far older link between these countries.
In very remote times species were, I believe, able to reach
certain areas such as Guatemala and western Mexico long
before the present Central America had come into existence,
that is to say long before Pliocene times. Dr. Gadow himself
urged that the Isthmus of Panama is but the last vestige of a
former much broader land connection between North and
South America (p. 248). In my opinion this should read
“the Isthmus of Panama contains some vestiges of a former
much broader land connection.”

To the uninitiated the Typhlopidae would seem feaely
related to the coecilians. Both are snake-like burrowing crea-
tures, and yet the former are true snakes and, therefore,
reptiles, while the others are merely limbless amphibians. On
_ close examination the true burrowing-snakes (Typhlopidae)
are found to be covered with minute cycloid scales, and to
exhibit other reptilian characters. Their distribution is ex-
tremely discontinuous and extensive, and they are largely
confined to solitary islands. That they possess no special
facilities for accidental dispersal across the ocean is evident,
and yet it is held by some zoologists that their presence on
islands, such as Christmas island for instance, can only be
due to such a cause. At any rate, the family exhibits all the
signs of antiquity, and, in the absence of any positive evidence
of accidentally distributed species, I am firmly convinced that
they spread by the usual method of slow migration on land.
Dr. Sarasin * places the dispersal of the family into pre-
Cretaceous times, in spite of the fact that we possess no
palaeontological evidence of their antiquity. All the same he

* Sarasin, F., “Tierwelt von Ceylon,” p. 75,

BURROWING SNAKES 258

is perfectly justified in doing so, because it can be shown from
various other tests that the great continents must have been
united by certain land connections, and that the present dis-
tribution of the Typhlopidae can be readily explained if we
assume that their dispersal took place at the same time. The
presence of T'yphlops tenuis in Guatemala and Mexico, on that
account, points to an ancient union between these countries
and to a survival in them of a relict fauna during a long course
of geological ages, in which the two countries may have been
separated.

I suggested above (p. 131) that the rattlesnakes, belong-
ing to the genus Crotalus, were of early Tertiary origin.
The centre of dispersal lies in the south-western States of
North America, all the species except one being confined
to that continent. The black-tailed rattlesnake (Crotalus
terrificus) is the only one which, according to Mr. Boulenger,*
ranges from south-western North America to South America.
Whether the South American species is identical with the
North American one is a matter in which authorities disagree.
All coneur, however, in the view that the genus Crotalus
reappears in South America in one or more forms, differing
but slightly from those inhabiting Mexico. And these South
American forms are not, as we might expect, confined to the
west coast, but have even penetrated to eastern Brazil, if
Mr. Boulenger’s records are reliable. At the same time it
seems as if their range in South America was very discon-
tinuous.

The fresh-water fish fauna of Central America is described
by Professor EHigenmann } as poor, the genera south of the
Isthmus of Tehuantepec being practically all South American.
The North American fauna is entirely distinct from that of
tropical America, the former not having contributed a single
element to the fresh-water fish fauna of South America. It
is interesting to compare this view with those founded on
other fresh-water groups such as the mollusks and crus-
taceans.

* Boulenger, G. A., ‘Catalogue of Snakes,”’ Vol. III., p. 573.
{ Higenmann, C. H., “‘ Freshwater Fishes of South America,” pp. 523
—622.

254 ORIGIN OF LIFE IN AMERICA

I suggested above (p. 161) that the fresh-water mussels
(Unionidae) probably effected their principal dispersal during
the Mesozoic Era, and that this circumstance might account
for the fact that we possess distinct proofs of a migration of
species from North to South America. The great genus Unio
has recently been subdivided by Dr. Simpson into numerous
genera. One group of Unio (Plagiola), ranging from Mexico
to the Mississippi drainage basin, reappears southward in
‘Nicaragua, another (Lampsilis) is known from Guatemala
to Yucatan. Other groups of Unio are confined to South
America, Unio-Tetraplodon occurs in Ecuador, having spread
from there into the Amazon valley. Unio-Castalina lives in
southern Brazil, Unio-Castaliella in Surinam and so forth.
Finally Unio-Diplodon principally inhabits Chile, Argentina
and Patagonia, while it reappears right across the Pacific
in New Zealand and Australia.

The range of these groups of Unio is apparently very com-
plex in South America. Nevertheless, I quite concur with Dr.
Simpson * in the belief that they all are the descendants of
certain members of the family Unionidae, which wandered
slowly from one river system into another, during the Triassic
or some later Mesozoic Period, from North America to South
America. To judge from the general distribution of the Unio-
nidae in South America, they entered that continent from the
west and only reached the eastern States subsequently. The
group Unio-Hyria, as Dr. von Ihering jf tells us, is nothing
but a modified Unio, which has comparatively recently pene-
trated from Guiana into Brazil. The most surprising fact
which is so strongly brought out in that author’s remarkable
researches is, that, while these Unionidae live in company with
other families of fresh-water mussels in eastern South
America, in Central America, Ecuador, Peru and Chile, that
is to say westward of the Andes, Unios alone occur. This con-
firms the opinion I expressed several times in previous chap-
ters, that the faunistic interchange between North and South
America took place between the western portions of the two
continents.

* Simpson, O. J., ‘Synopsis of the Najades,” p. 507.
| Ihering, H. von, * Archhelenis und Archinotis,” p. 122.

ar 5) es td

FRESHWATER CRABS 255

The fresh-water crabs (Potamonidae) must have invaded
Central America from the south. The family is confined to
southern Asia, southern Europe, Africa, South and Central
America. Except for a few species in Mexico, fresh-water
crabs are entirely absent from North America, nor do we
possess any evidence of their ever having lived there.* A
comparison with the range of Unio is, therefore, of particular
interest. The two South American groups of fresh-water
crabs apparently spread westward from eastern South
America, that is to say in a direction opposed to that taken
by the Unios. We need only consider the northern group
which, to judge from its range, is much the oldest. ‘Dr.
Ortmann } distinguishes the three genera Kingsleya, Hpilo-
bocera ‘and Pseudothelphusa. Kingsleya only occurs in
Guiana, while Epilobocera is peculiar to the Greater
Antilles. The third genus, Pseudothelphusa, ranges from
the Amazon through Guiana, Venezuela and Colombia north-
ward as far as Mexico, and south-westward to Ecuador, Peru
and Bolivia. There are quite a number of endemic species of
fresh-water crabs in Central America. Yet are we to conclude
from this fact that a slow migration took place across the
long isthmus since Pliocene times ? On the contrary, if, as
Dr. Ortmann suggests, the genus Epilobocera arose in the
West Indies from some ancestral Central American Pseudo-

thelphusa, that event must have happened in much more

remote times. It is customary to assume that the great mass
of the South American fauna, including mammals, birds,
reptiles, fishes and invertebrates all surged across the newly
opened highway towards Mexico in the Pliocene Period. If
Epilobocera succeeded subsequently in crossing from Central
America on a land bridge to Cuba, Haiti and Portorico, how
can. we account for the fact that the existing faunas of Central
America and the Greater Antilles do not show more affinity
to one another than they actually do? As compared with
Central America the mammalian fauna of the West Indies
is strikingly distinct and poor in species. We have also to
take into consideration that certain species of Pseudothelphusa

* Rathbun, Mary J., “ Freshwater Orabs of America.”

+ Ortmann, A. E., “ Distribution of Freshwater Decapods,” pp. 306—
309.

256 ORIGIN OF LIFE IN AMERICA

possess a remarkably discontinuous range. Pseudothelphusa
eolombiana inhabits the United States of Colombia. In the
extreme western end of Panama, in the Chiriqui region, it
occurs at a height of 4,000 feet, and a thousand miles north
of this locality it is met with in Mexico. All along the great
isthmus, on the other hand, there are isolated localities in
which distinct species are found. Both the ranges of Unio
and Pseudothelphusa in Central America seem to me more
in agreement with the theory of the existence to the west of
Central America of an ancient continuous land surface uniting
Colombia and certain parts only of Central America, while the
rest of the latter was still largely submerged.

One of the chief zoogeographical features in the range.of the
land and fresh-water mollusks of Central America consists in
the intermingling of South and North American forms within
the limits of this area, rather than in the endemic species, and
in the relationship of the molluscan fauna to that of the West
Indies.* The affinity of the Antilles with South America,
however, is much more pronounced than with North America,
if we exclude Mexico. The distinctly endemic elements of
Central America and the West Indian islands appear to have
invaded both North and South America to some extent.
The family Helicinidae for instance, as I mentioned (p. 157),
is probably of semi-tropical origin, its range indicating that it
has reached America from the west, establishing itself
primarily in Central America and the West Indies at a very
remote time of geological history. The operculate land mol-
lusks, to which the Helicinidae belong, are of great faunistic
interest. Let us take for example the large family Cyclo-
phoridae, which has its headquarters in southern Asia and
southern Europe. In America the family is almost limited to
Central and South America and the West Indian islands.
Only in Mexico does it touch North American territory. As
the geographical distribution of the family is now fairly well
known, a great deal of interesting information can be derived
from its study. The genus Cyrtotoma is peculiar to southern
Mexico. Its nearest relations are Buckleyia of Colombia and
Ecuador, and Crocidopoma of Haiti, Cuba and Jamaica. The

* Martens, L. von, “ Mollusks of Central America,” p. xiv.

EUROPEANS IN CENTRAL AMERICA 257

larger genus Amphicyclotus has its centre of dispersal in
Colombia and Ecuador. From there it pressed eastward
through Venezuela into Guiana and across Trinidad to the
island of Martinique, which must have been connected for
some time with the southern mainland. In Central America
the genus has a discontinuous range. A few species occur
in Costa Rica, Guatemala and southern Mexico. Nota single
species is known from the Greater Antilles.

There is one very important feature in the fauna of Central
America which I have scarcely dwelt on as yet, and that is its
affinity with Europe. It is not at all striking. Yet it does
exist. The large group Diplommatininae belonging to the
family Cyclophoridae is almost entirely confined to southern
Asia, the Pacific islands and Australia.* Only the single
genus Adelopoma occurs in America. Its wide and extremely
discontinuous range in the New World marks it as a very
ancient immigrant, for it is likewise known from Argentina,
Peru, Guatemala and Trinidad. Now the Guatemalan species
(Adelopoma stolli) has its nearest relation in the Miocene
beds of Oppeln in Silesia, for Professor Andreae + informs
us that the fossil Adelopoma martensi occurring in these
deposits is scarcely distinguishable from: a species inhabit-
ing Central America. Our first impulse on hearing of
this extraordinary discovery is to attribute. it to con-
vergence or even misidentification. But the identifica-
tion has been confirmed by Professor Boettger, one of the
most eminent of Huropean specialists, while Adelopoma
stolli is not by any means the only Central American
land mollusk that possesses Kuropean affinities. Many other
instances will be alluded to in the next chapter (p. 265).
Those who wish to interpret all cases of intimate relationship
between American and European forms, as arising from a
remote migration across a hypothetical Bering Strait land
bridge, will find it difficult to reconcile this particular occur-
rence with the fact that no Adelopomae inhabit any part of
Asia or North America.

Professor Stoll,{ who made a special study of the mites of

* Kobelt, W., “ Cyclophoridae.”

{ Andreae, A., ‘ Binnenconchylienfauna von Oppeln,’’ IL., p. 23.

} Stoll, O., “‘Zoogeographie d. Wirbellosen,’’ pp. 19—20.

L.A. S

258 ORIGIN OF LIFE IN AMERICA

Guatemala during a residence there of several years, states
that the mite-fauna of Central America is composed of the
same genera as that of middle Europe. In some cases even
the species are identical. It is true that most of these genera
also inhabit Asia, though Linopodes, Haplophora, Nicoletiella
and Uropoda have not yet been recorded from that continent.
As some of these are known from the Oligocene Baltic amber
deposits, it is probable that the genera date back to ‘at least
early Tertiary times.

Of the nearly related spiders and harvestmen, Mr. Pickard-
Cambridge * remarks, that while the majority of the Central
American species are peculiar to the Nearctic and Neo-
tropical regions, the genera are in many cases identical with
those of the Mediterranean region, India, Australia or Africa.
There are not now in existence any land connections, he con-
cludes, which an arachnidal fauna could take advantage of
in order to pass from Africa, Australia or Europe to North
or South America, and we can only suggest that at some
period or other these now widely separated regions must
have been linked together by land which has long since dis-
appeared.

The various groups of Central American insects are as yet
far from well known, and their relationships with the insects
of other regions have been but imperfectly determined, not-
withstanding the fact that Messrs. Salvin and Godman have
published a series of fine volumes about them. The consensus
of opinion of the writers, who have contributed to the
“ Biologia Centrali-Americana,”’ is that Central America
is essentially a part of South America. The purely North
American forms are few in number, their southern limit being
as a rule in Mexico. This verdict agrees also with that of
Dr. Calvert,> who in his recent researches on the dragon-
flies (Odonata) of Mexico and Central America, comes to the
conclusion that in the endemic as well as in the non-endemic
species, the South American element is much the strongest.

Before concluding this chapter, I might again emphasize
the fact that the occurrences of northern genera and species
in Central America are almost all discontinuous. I need only

* Pickard-Cambridge, O., “ Araneida of Central America.”
+ Calvert, P. P., “ Odonate Fauna of Central America,” p. 467.

ee I AOL
- yng

DISCONTINUOUS DISTRIBUTION 259

mention among northern plants, the oak (Quercus) and the
plane (Platanus), among animals, the newt Spelerpes, the
snapping turtles (Chelidridae) and the fresh-water mussels
(Unionidae). Many other northern animals and plants have
a similar disjointed range in the midst of an entirely alien
southern fauna. These, and the northern groups that are
altogether absent from Central America, but reappear much
further south, are, I think, part of a very ancient invasion of

‘South America. If itis true that the South American animals

and plants which have taken almost complete possession of
Central America, poured into the latter from the south in
early Pliocene times, surely the northern groups must be
immeasurably older! In their discontinuous range and fre-
quent isolation on mountain tops they show every sign of
antiquity, and it seems likely that they are being crowded
out rapidly by their stronger southern rivals, which are better
fitted to support the present climatic conditions of this region.
Dr. Wallace * suggested, as I mentioned above, that the
northern faunistic affinity of South America which is so cha-
racteristic, especially of Chile, but which we find to some
extent all along the Pacific coast, is mainly due to the Glacial
Epoch. He fancied that a migration, aided by gales and hurri-
canes during successive Glacial Epochs, when the mountain
range of the Isthmus of Panama, if moderately increased in
height, might have become adapted for the passage of northern.
forms, would explain all these extraordinary features of distri-:
bution. Dr. Wallace thought the resemblance only consisted
in a few plants and insects. He had very little idea of the real
extent and character of the northern element that has actually
penetrated into Central and South America. It is unlikely
that he would have supported these views had he known
of the range of the newts, turtles, freshwater mussels and
other groups. Moreover, we also have evidence of ancient
migrations of mammals and other animals, as well as plants,
in an inverse direction from the south to the north. It is
perfectly certain, therefore, that long anterior to the southern
invasion into the existing area of Central America, two
streams of animals and plants passed between the great

* Wallace, A. R., “ Distribution of Animals,” IL., p. 45.
s 2

260 ORIGIN OF LIFE IN AMERICA

continents, leaving certain traces of their transit in the
more ancient portions of the country. And yet I believe, and
shall produce ample evidence in support of my contention,
that only certain fragments of Central America formed part
of that land which long ago served as the highway between
North and South America. This fact is not so readily re-
vealed from a study of the Central American animals and
plants. All we can gather from our present researches is
that there are certain ancient elements in the fauna and flora
of Central America exhibiting affinities with North America,
Asia, Europe, Africa, the West Indies and South America, and
that these older elements are being dispossessed or driven into
the more inaccessible parts by the members of the new and
most recent invasion from the south which traversed the newly
formed Central American isthmus. It is believed that this
must have commenced in Pliocene times. Of the two marine
barriers which previously prevented this southern advance,
one was in the neighbourhood of the Panama Canal, the other
at the Isthmus of Tehuantepec, but to judge from the animals
and plants of Central America, the former had already dis-
appeared when the more northerly one was still in existence.

CHAPTER XI
THE WEST INDIAN ISLANDS

Nort and South America are to be regarded, according
to Professor Suess,* as two essentially distinct land-masses,
between which is interposed, as a third element, the area of
Central America and the Antilles. This geological distinct-
ness of Central America and the Antilles from the two neigh-
bouring continents is scarcely recognisable in the fauna of the
great isthmus. But the West Indies are comparable to a
wedge driven in between two faunistically, more or less, in-
dependent and distinct land masses. Almost everyone who
has dealt with the fauna or flora of the West Indian islands
has expressed his surprise at this fact. In position, says Dr.
Wallace,f the Antilles form an unbroken chain uniting North
and South America, in a line parallel to the great Central
American isthmus. Yet instead of exhibiting an intermixtura
of the productions of Florida and Venezuela, they differ
widely from both these countries, possessing in some groups
a degree of speciality only to be found elsewhere in islands far
removed from any continent.

One other important feature which strikes the visitor to
the islands is their extreme poverty in the higher groups of
animal life.’ It is not that the Antilles are climatically un-
favourable to animal life. On the contrary, they are excep-
tionally favoured by nature to support a luxuriant and varied
fauna and flora. Their temperature is high and uniform,
there is an abundance of moisture, the soils are very fertile,
while high mountains as well as gentle plains abound, at least
in the larger islands. Cuba, the largest of them, exceeding
Ireland in size, and being far more favourably situated, has

* Suess, E., “‘ Antlitz der Erde,” I., p. 700.
+ Wallace, A. R., “ Distribution of Animals,” IT., p. 61.

262 — ORIGIN OF LIFE IN AMERICA

not half-a-dozen species of land mammals, while Ireland pos-
sesses nearly three times that number. There are only two
ways in which we can account for this great deficiency in the
‘higher animal life on the Antilles. We may suppose that
either the islands have not been connected with the mainland
since early Tertiary times, or if they have, that their fauna
was largely destroyed since their isolation. In the latter
case the apparent poverty of the fauna might be due to great
destruction of animal life during a submergence of the land,
and the consequent reduction of the habitable area. On the
other hand, we should expect the relict fauna of the islands to
exhibit marked affinities with that of the two great continents
lying to the north and south respectively. However, as I
have mentioned, the fauna on the whole is essentially dis-
similar from that of North and South America. The problem
of the origin of the West Indian fauna, therefore, like that of
Centra] America, is much more complex than it would at first
sight appear. I alluded to the apparent poverty of the fauna
because, although it does appear very poor in the higher groups
some of the lower forms of animals are represented by a large
number of species. The land-snails, in fact, are extremely
varied in character, and the abundance of species is one of the
most remarkable features of the West Indian fauna. A study
of their distribution and their relationship will probably
give us a better insight into the origin of the fauna as a whole
than the higher vertebrates, which are so poorly represented
on the islands.

Before describing the molluscan fauna of the Antilles, a
few preliminary remarks on the islands may not be out of
place. The islands as a whole form a natural breakwater or
barrier between the Atlantic Ocean on the one hand, and the
Gulf of Mexico and the Caribbean Sea on the other, which
lie on the opposite side of it (Fig. 13). A mere glance at the
map is sufficient to show that we have to deal with two distinct
sets of islands. A series of large ones belong together, viz.,
Cuba, Haiti or San Domingo, Jamaica and Portorico, with
mountain crests running in an east-westward direction, while
a chain of the much smaller, Anguilla, Guadeloupe, Dominica,
Martinique, St. Vincent, Barbados and others, placed in north

and southward position, constitute quite an independent

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GEOLOGY OF THE WEST INDIES 263

group. ‘The former are always spoken of as the ‘“ Greater
Antilles,’? and the latter.as the ‘‘ Lesser Antilles.”” With
Professor Suess * we may look upon the mountain ranges of
Yucatan and Guatemala, which trend in a west-easterly direc-
tion, as the western continuations of the mountain system of
the Greater Antilles. The latter, as well as a few of the
northern Lesser Antilles, are composed of sedimentary rocks
of Mesozoic and Cainozoic, possibly even of Palaeozoic age,
while many of the remaining smaller islands, which cluster
together in a concave arc, seem to be of comparatively
recent volcanic origin. The Bahamas, and some of the
more southerly flat islands, including part of Barbados, are
apparently of young Tertiary age. The whole of the main
series of the Antilles, from Cuba through Jamaica, Haiti and
Portorico to Barbados, is composed of similar rocks. Granite,
older eruptive rocks, serpentine, glauconitic sandstone and
cretaceous limestone, form the visible remnants of a once
connected mountain range. Westward the latter divides into
several branches. One of them passes from southern Haiti
through Jamaica to Honduras, another by way of Cuba to
Guatemala.

There is some evidence, according to Professor Hill, that
the east coast of North America lay far eastward of its pre-
sent site in pre-Cretaceous times, whereas some faunistic
facts point to a continuation of this condition until the
Tertiary Era. The Pacific marine fauna transgressed east-
ward during the Jurassic Period, probably across the Mexican
plateau, fossils of Pacific type having been found in western
Cuba. This implies that the barrier separating the Atlantic
from the Pacific in those remote times must have been situated
to the east of Cuba. Professor Hill} argues that the chain
of low-lying islands between Florida and north-eastern South
America represent the remnants of this ancient Jura-Cre-
taceous isthmus between the two great continents. Whether
such a land bridge existed is difficult to determine from
faunistic evidence, but the Atlantic waters seem to have
entered the Caribbean Sea in Lower Cretaceous times.
During part of the Hocene and Oligocene Periods, extensive

* Suess, E., ‘‘ Antlitz der Erde,” I., pp. 700—707.
+ Hill, R. T., ‘Geology of Jamaica,” pp. 200—216.

264 ORIGIN OF LIFE IN AMERICA

subsidences drowned the Antilles to such an extent, accord-
ing to Professor Hill, that only the higher summits of Cuba,
Haiti and Jamaica remained above sea-level as small islands.
The West Indian islands were subsequently raised into a large
continuous and connected land. In late Miocene and Pliocene
times the gradual and final dismemberment of the Antillean
lands took place. Still more recently a further elevation
occurred, not sufficient, however, to establish a united
Antillean continent. Whether Professor Schuchert* supports
Professor Hill’s hypothesis of a wide land connection be-
tween Florida and Venezuela in late Jurassic times is not
clearly indicated in his maps. But during the Cretaceous
Period all the West Indian islands except the Bahamas are
represented as being entirely submerged. In Eocene tim’es
the greater part of Cuba was above sea-level. In the succeed-
ing Oligocene Period all the islands, except the Bahamas,
once more disappeared. Thenceforth all the Greater Antilles
retained their present outlines. Only during the Plio-
cene Period was there a land connection between Cuba and
Yucatan. All these writers thus concur in the view that some
time during the earlier part of the Tertiary Era there was a
very profound and widespread subsidence of almost the whole
of the Antillean area. Yet, according to Professor Schuchert,
the Bahamas, or some land area in the position of the
Bahamas, if I correctly interpret his maps, remained above
sea-level practically from the earliest Paleozoic ages to the
present day. The idea that there was once a land connection
between North and South America along the chain of the
Lesser Antilles, Cuba, the Bahamas and Florida is also
advocated by Professor Gregory,f though he-admits that
the area of the Windward islands was submerged at the period
when the oceanic deposits of Barbados were laid down. There
is no adequate evidence, he thinks, to show that there was
more land at any subsequent time in this region than there
is at present. |

Now as for the light thrown on these various problems
by a study of the geographical distribution of the West Indian -

* Schuchert, Charles, ‘‘ Paleogeography of North America,” Maps 89—

100.
' + Gregory, J. W., “Geology of the West Indies,” p. 305.

SNAILS OF THE WEST INDIES 265

land mollusks, it may be urged, in the first instance, that the
value of the evidence is greatly impaired by the possibility
of occasional or accidental dispersal. That a certain per-
centage of the fauna of an island is due to importation by
human agency is, I think, well established. That a small
proportion of the West Indian fauna may possibly have been
carried from island to island and from the mainland by other
accidental means is likewise possible. But I quite concur
with Dr. Simpson in his belief that we are not justified in
explaining the whole distribution of the terrestrial mollusks in
the West Indian islands by such an hypothesis. The very
nature of the West Indian fauna, and its distinctness from
that of the neighbouring continents, precludes the assumption
of any extensive accidental dispersal. Hence we may take for
granted the correctness of the theory that the main mass of
these mollusks have migrated from island to island when the
latter formed a united land surface. This belief is vouched
for, moreover, by the fact that the study of practically all
other groups of West Indian animals brings us to precisely
the same conclusion. In their general agreement with the
results arrived at from a geological study, all these groups
tend to show that the study of geographical distribution is a
science of profound importance as an indicator of former
changes of land and water.

The facts adduced by Dr. Simpson, that the operculate
species form so large a proportion of the Antillean land-
snail fauna, that a majority of the genera is found on two
or more of the islands and the mainland, while nearly every
species is absolutely restricted to a single island, is a strong
testimony in favour of a former general land connection in
this area. Dr. Simpson * very carefully compared the mol-

- lusean fauna of the various islands with one another and with

that of the mainland, and bases his conception of the geolo-
gical history of the Antilles mainly on the results so derived.
He believes a considerable portion of the species inhabiting
the Greater Antilles to be ancient, and to have developed on
the islands where they are now found. Probably some time

* Simpson, OC, T., “ Distribution of Mollusks in West Indies,” pp. 447—
448,

266 ORIGIN OF LIFE IN AMERICA

during the Hocene Period the Greater Antilles were at a
higher level, so that the islands were united with one another
and with Central America. This resulted in an exchange of
species between the two regions. A land connection is also
indicated between Cuba, the Bahamas and Florida. At this
time, he thinks, the more northern isles of the Lesser Antilles
were not yet elevated above the sea, or, if so, they have since

probably been submerged. After this period of elevation

there followed one of general subsidence. During it Jamaica
was the first island to be separated, then followed Cuba, and
afterwards Haiti and Portorico. The connection between
the Antilles and the mainland was broken, while the subsi-
dence continued until only the summits of the mountains of
the four Greater Antillean Islands remained above water.
Eventually there was another period of elevation which lasted,
no doubt, until the present time. The Bahamas gradually
emerged and were populated by forms drifted from Cuba and
Haiti. In this last conclusion Dr. Simpson unfortunately
fails to appreciate the full value of his own studies. If all
the snails, amphibians and reptiles known to inhabit the
Bahamas—and many of them are peculiar to these islands—
had reached them by accidental dispersal, this mode of con-
veyance must be of enormous importance. In such a case
I think we should scarcely be justified in basing our theories
of the geological history of the Antilles on the geographical
distribution of animals.

Now among the families of snails alluded to in Dr. Simp-
son’s paper as being abundant in the West Indies, there are
some that have received special attention by American
malacologists. One of these, the Urocoptidae, or Cylindrel-
lidae as they were formerly called, comprises small snails
with an elegant fusiform shell composed of many narrow
whorls. They are found in the Antilles, in southern Florida,
along the northern coasts of South America, in Central
America and in Mexico, as well as the adjacent parts of the
United States. The centre of distribution thus lies in the
West Indies. |

Since it has been proved by fossil evidence in Jamaica that

“numerous sub-generic groups of land snails, in essentially
_ their modern forms, were established before the close of the

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ANTIQUITY OF SNAILS 267

Oligocene Period, generic differentiation probably dates from
a much earlier time. Indeed, Dr. Pilsbry * is of opinion that
the first radiation of the Antillean group of the Urocoptidae
may have occurred on a Mesozoic Antillean land area. The
succeeding Eocene depression, he thinks, isolated various
branches of the existing stocks, western Cuba being pro-
bably the first fragment to be dismembered. It was probably
not until near the close of the Tertiary that continuity of
land was restored with east Cuba. Haiti and Jamaica would
seem to have remained united after both western and eastern
Cuba had seceded. Finally, these islands were widely
separated by the subsidence culminating at the end of the
HKocene, or in the beginning of the Oligocene Period. ‘This
depression was again followed by an elevation in later Oligo-
cene times, and it is likely that there was a transitory connec-
tion between Jamaica and Haiti. Between the latter and
Cuba the land connection probably lasted longer, thus pro-
ducing the homogeneous distribution of several groups. It
is likely, says Dr. Pilsbry, that during this mid-Oligocene
elevation, the Haitian land included Portorico, the Virgin
islands and the islands of the Anguilla bank, that is to say,
some of the northern group of the Lesser Antilles. Dr.
Pilsbry argues that the presence of large fossil mammals of
South American type (Amblyrhiza and Loxomylus) in Plio-
cene deposits of Anguilla demonstrates that the whole Carib-
bean chain of islands was elevated into a ridge connected
with South America during the Pliocene Period. He likewise
expresses the opinion that the genus Brachypodella, one of
the Urocoptidae, extended its range westward to Yucatan.
Nevertheless, he contends that there is but scanty evidence of
any direct land connection between the Greater Antilles and
the mainland of Central America during the whole of Tertiary
time.

Thus, while differing from Dr. Simpson on several minor
points, Dr. Pilsbry’s careful researches confirm his view,
and that of many geologists, that originally there was a large
area of land of which the Antilles are the last remnants, and
that some time during the Tertiary Era almost the whole of

* Pilsbry, H., “ Manual of Conchology,” XVI., pp. xx.—xxiv.

268 ~ ORIGIN OF LIFE IN AMERICA

this old land was submerged having since gradually regained
its present position. :

The great age of the West Indian fauna and the inter-re-
lationship between the islands and the mainland is well exem-
plified by the ancient family of operculate snails—the
Cyclophoridae.* The genus Neocyclotus inhabits principally
northern South America and the Antilles. From this
apparently very old centre of dispersal some members of
the genus have pushed southward as far as Peru in the west
and Rio de Janeiro in the east. A few have entered Central
America. One distinct group (Plectocyclotus) has no less
than thirty-two species in Jamaica and only one in Portorico.
Another genus (Crocidopomai) is entirely confined to Jamaica,
Haiti and eastern Cuba. This indicates strikingly the re-
lationship of the three Great Antilles and their distinctness
from western Cuba, which was already pointed out by Dr.
Pilsbry, while geologists maintain that western Cuba was
submerged quite independently from the remainder of the
islands. It also illustrates the extreme slowness with which
the dispersal of these mollusks takes place.

Still more instructive is the whole group to which
Crocidopoma belongs. With Cyrtotoma, Amphicyclotus and
Buckleya, it forms, as already mentioned (p. 256), a group
of closely related genera of operculate snails. I alluded
also to the fact that three of them had a discontinuous range
in Central America, and that Amphicyclotus had apparently
travelled eastward from Ecuador, invading Venezuela and
Guiana, and had thence passed into the islands of Martinique,
Guadeloupe and Dominica, when the latter were connected
with one another, and with the mainland. It might be
urged that accidental dispersal is responsible for their
presence on these islands. ‘But we have no reason for such a
supposition, because the species occurring on the islands are
quite distinct from one another and from those of Venezuela.
Some evidence is afforded by these snails for the belief that
the Lesser Antilles are remnants of older land which ex-
tended northward from Venezuela, although all the visible
parts of the islands are covered by modern volcanic deposits.

* Kobelt, W., “‘ Cyclophoridae.”

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DISPERSAL OF SNAILS 269

We are too apt to argue that the fauna of an island covered
by recent volcanic deposits must necessarily have been derived
by occasional means of dispersal. I need only cite the case of
the Galapagos islands, which are entirely volcanic, and have
seemingly risen from the floor of the ocean. Nevertheless,
it can be demonstrated from a faunistic point of view, as I
shall show later on, that they have once formed part of an
ancient continuous land surface.

Still another group of operculate land snails contains the
two genera Megalomastoma and Tomocyclus. The centre
of dispersal is Cuba, chiefly the western part of the island.
From there Megalomastoma reached Haiti, Portorico and the
Virgin islands, which lie close to the latter. Tomocyclus
inhabits only southern Mexico and Guatemala. Thus it
seems probable that Cuba, Guatemala, and southern Mexico
were connected with one another by land in very remote
times.

Let us take as another example, that of the ancient and
large family Bulimulidae. In another chapter I have dwelt
on the great age of this family of snails (p. 209) and its
general range. It contains mostly large, ponderous snails
with somewhat conical shells. Anatomically they ‘are re-
lated to the Helicidae. Although represented by a great
many species, only a few genera enter the West Indies. One
of these (Plekocheilus) inhabits almost exclusively Guiana,
Venezuela, Colombia, Ecuador, Peru and Bolivia, that is to
say the northern and western States of South America, where
the different species are often found at great heights in the
mountains. Only two species enter the West Indies, viz.,
P. aurissileni, which is peculiar to St. Vincent, and P. aula-
costylus, which is only met with in the island of St. Lucia.
These islands are two of the most southern group of the
Lesser Antilles. The ancestors of the two species of Pleko-
cheilus have probably entered these islands when the latter
were connected with one another and with the mainland of
Venezuela, and, as the species are very distinct from one
another, this could not have happened within very recent
geological times.

The species of the genus Bulimulus, as I have already had
occasion to state, are exceedingly difficult to discriminate

°

270 ORIGIN OF LIFE IN AMERICA

from one another. Dr. Pilsbry divided them roughly into
three groups, only one of which inhabits the Antilles. To
trace the relationship of the various species to one another
seems to be a task even beyond the powers of this distin-
guished American conchologist. The minor sections being
arranged geographically in Dr. Pilsbry’s work, it does not
enable us to draw any conclusions as to their former dis-
persals. One interesting fact, however, has been brought to
light, which proves not only the antiquity of this family but
the extraordinary persistency of specific characters among
some of its members. The Oligocene Bulimulus americanus
of Florida is practically identical with B. ridleyi, still living
on the island of Fernando de Noronha.

The genus Drymaeus (Otostomus), which is as difficult to
classify as Bulimulus, has mainly a continental range.
Only a few species live in the West Indies. Among these
we likewise notice a remarkable persistency of specific
characters. Drymaeus dormani, for instance, occurs in
southern Florida, while the closely allied D. dominicus is
resident in Haiti, Cuba, Florida, Yucatan, Nicaragua and
Mexico. At the first thought we might feel inclined to attri-
bute such a strikingly discontinuous range to accidental dis-
tribution ; but a careful study of the whole family has im-
pressed me with the conviction that we have to deal with a
set of very ancient and very persistent types of mollusks.

Even less satisfactory to identify than Bulimulus and
Drymaeus are the Orthalicinae, another large group of Buli-
mulidae, Dr. Strebel * has recently undertaken their revision,
utilising several characters which had hitherto not been em-
ployed in the discrimination of the species. It is an attempt,
at least, to trace the complex relationship of the innumerable
closely allied forms, although the author does not seem to
realize the great antiquity of the group. His arguments in
favour of wholesale accidental dispersal, even from western
Mexico to the Antilles, are quite at variance with the lesson
the study of the West Indian fauna has taught us. The species
of Simpulopsis are mostly South American, but a small aber-
rant group with smooth apical whorls is confined to Portorico,

* Strebel, H., “ Revision der Orthalicinen.”

MOLLUSCAN AFFINITIES 271

Haiti and Mexico. The genus Gaeotis is quite confined to
Portorico, while Amphibulima is limited to the Lesser
Antilles.*

All these studies yield the same fundamental results,
namely, the presence within the Antillean area of an ex-
tremely ancient stock distantly related to that of Central
America and northern South America. After this fauna
had developed to some extent, a widespread destruction
apparently took place, due probably to submergence, fol-
lowed by a reimmigration from the south and west. A
more precise knowledge, however, of the minor physical
changes which the West Indian islands have undergone
can be acquired when we compare the results derived
from the sedentary or slowly moving mollusks with those
drawn from the more active members of the fauna. But
there is one more element of importance in the Antillean
molluscan fauna which has not yet been considered. It
is especially in view of the remarks I made in the ninth
chapter, on the striking relationship of the south-western
American fauna to that of Europe, that I wish to direct par-
ticular attention to the European affinities of the Antillean
fauna.

I think it was Dr. Kobelt + who first animadverted on the
resemblance between the European molluscan fauna and that
of the Antilles and Central America. At first sight, as he
remarks, the two faunas seem to be as distinct as any disciple
of the principle of multiple centres of creation could wish.
After a careful study, however, we certainly perceive distinct
traces of relationship. The carnivorous snail Glandina, which
is represented in the Mediterranean region of Europe by a
single species, has its headquarters in the Antilles and in
the surrounding States. It cannot be looked upon as a recent
introduction to Hurope, because its discontinuous range be-
between the Caucasus and Algeria is altogether opposed to any
such supposition. Several species of Glandina, moreover,
occur in French and English Eocene, Oligocene and Miocene
deposits, some of them being almost identical with still

* Pilsbry, H. A., “ Manual of Conchology,” Vols. X.—XII.

+ Kobelt, W., “ Verhaltniss d. Europaiischen Landmolluskenfauna, &c.,’’
p. 145—148.

272 ORIGIN OF LIFE IN AMERICA

existing American forms. The operculate genera Tudorella
and Leonia of the Mediterranean region are certainly related
to West Indian forms, though not so closely as was formerly,
believed. These and other considerations induced Dr. Kobelt
| to postulate a land connection between Europe and North
America, which was only severed in Miocene times. The
German Miocene genus Subulina, the large Glandinae and the
early Tertiary Huropean Oleacinae, are considered by Pro-
fessor Boettger * as the nearest relations or direct ancestors
of Central America or West Indian genera and species.. The
“same authority also alludes to the American facies of the
Tertiary flora of Europe, and concludes that a land bridge
right across the Atlantic Ocean existed up to early Miocene
times. Finally Professor Andreaet supports the same theory,
on account of the occurrence of the West Indian Boltenia,
Strobilus and Pleurodonte in the Miocene deposits of Silesia
_in Germany. And he was the first to definitely fix the posi-
tion of the land connection as one uniting western Europe
with the Antillean area.

Still other features of relationship between these regions
remain to be considered. Long ago Mr. Woodward { pointed
out that the presence of the Huropean genus Clausilia in the
West Indies and in northern South America (see Fig. 19)

» implied the existence of a former more direct land way across
the Atlantic than would be afforded by the land connection
which was supposed to have once united the boreal regions
of Kurope and North America. Since that time others have
repeated his assertion. Clausilia is now known to have lived
in Europe since Cretaceous times, and has probably originated
there. It is partial to high altitudes, large numbers of species
being found in the Alps, the Dalmatian mountains and the
Caucasus. Only a single European species resembles the
American group (Nenia), namely Clausilia pauli of the
western Pyrenees, and it is so closely related to the members
of that group that both Mr. Bourguignat and Mr. Locard,
two French conchologists of the ‘‘ nouvelle école,’’ failed to
find any satisfactory difference between them. It is quite
* Boettger, O., “‘ Verwandschaftsbeziehungen d. Helix Arten,”’ p. 116.

+ Andreae, A., ** Binnenconchylienfauna d. Miocins,’’ IT., p. 31.
{ Woodward, S. P., “ Manual of the Mollusca,” p. 112.

Kerapaeet

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MOLLUSCAN AFFINITIES 273

true that another group of Clausilia, known as Garnieria, from
tropical and eastern Asia also approaches the American group
closely. Yet the fact that no Clausilia, either fossil or recent,
has ever been discovered in northern Asia or North America,
although many species, as I remarked, thrive in high altitudes
and cold climates, speaks strongly against the supposition of
the ancestors of the West Indian and South American stock
having wandered through Asia and North America to these
regions. The geographical distribution of Clausilia thus
offers one of the most cogent arguments in favour of a direct
land bridge between the Mediterranean and the Antillean |
regions. Opponents of this view may urge that Clausilia is
merely represented by a single species in the West Indies,
while none are known from Central America. ‘We may explain
this curious circumstance by the fact that the West Indies
were submerged probably before the newly immigrated Clau-
silias had time to gain possession of the higher eminences,
so that most of them would have been destroyed. In Central
America fewer traces of European affinity have been detected
than in western North America or western South America,
because in the latter regions the faunas remained more or less
isolated for long periods, while the great rush of South
American invaders, combined with climatic changes, swept
all before them in Central America. Why Clausilia has suc-
ceeded in reaching western South America without attaining
western North America will be discussed in the next chapter
but one. :

Dr. Simroth suggests that the ancestors of the American
Bulimulidae, at least the group of Orthalicinae, may be of
Kuropean origin, while I venture to think that the curious
Rumina decollata, which is supposed to be a human importa-
tion in Cuba, may be indigenous there, since it is now known
to have lived unchanged in the Mediterranean region since
Oligocene times. In view of my remarks in previous chapters
on the relationship of the North American snake Tropido-
notus, of the crayfish Potamobius, of the slugs belonging
to the family Arionidae, of the glass snake, of all that remark-
ably Huropean assemblage of animals in the south western
States, of the snail Adelopoma in Guatemala and numerous

other instances, such as the range of the flamingoes, it need
L.A. z

274 ORIGIN OF LIFE IN AMERICA

not be surprising that I am a strong adherent of the theory
just stated, that a land bridge existed right across the Atlantic
between the Mediterranean and the Antillean regions, and
that the Huropean element of the fauna made use of it in
passing to America (Fig. 14). This land connection, of
course, was quite independent of the one I described (p. 18)
as having once joined Labrador and Scotland by way of
Greenland. The latter may possibly have come into existence
when the other had already crumbled away. At any rate, the -
two are quite distinct as to age and position.

Before I had an opportunity of making this more thorough
study of the North American fauna, I was under the impres-
sion that the “ Southern Atlantis,” as we may call this land
connection, joined Africa with South America, and that there
was no other land bridge across the mid-Atlantic.* I am still
an advocate, as I shall explain more fully later on, of what
Dr. von Ihering calls “ Archhelenis,” the hypothetical con-
tinent of the southern part of the Atlantic Ocean. But I
maintain that a more northerly land bridge likewise existed,
and that the two were completely separated by a wide ocean.

The disciples of Dr. Wallace will exclaim, ‘‘ What about the
permanence of ocean basins, a theory which receives such
weighty support from some of the most eminent geologists
of the day?” This question of the permanence of ocean
basins, and we may say of continental areas too, really lies at
the root of most of our inquiries into the past changes of the
earth and its animal inhabitants. The internal characters
of the rocks we see around us, remarks Sir Archibald Geikie,f
point unmistakably to deposition in comparatively shallow
water. “‘Their abundant intercalations of fine and coarse
material, their constant variety of mineral composition, their
sun-cracks, ripple-marks, rain-pittings and worm-tracks,
their numerous unconformabilities and traces of terrestrial
surfaces, together with the prevalent facies of their organic
contents, combine to demonstrate that the main mass of the
sedimentary rocks of the earth’s crust was accumulated close
to land, and that no trace of really abysmal deposits is to be
found among them.’”’ From these considerations, says Sir

* Scharff, R. F., “ Atlantis Problem,” p. 279.
+ Geikie, A., ‘Text Book of Geology,” p. 911.

THE ANCIENT ATLANTIS | 275

Archibald Geikie, we are led to the conclusion that the pre-

sent continental areas must have been terrestrial regions

of the earth’s surface from a remote geological period.
Subject. to repeated oscillations, continues Sir Archibald
Geikie, so that one tract after another has disappeared
and reappeared from beneath the sea, the continents,
though constantly varying in shape and size, have yet
maintained their individuality. So far, I think, most
geologists will agree with Sir Archibald Geikie. It is his
inference, that the existing ocean basins have probably always
been the great depressions of the earth’s surface, which has
not met with such general approval. Dr. Wallace supports
Sir Archibald Geikie’s view on the grounds, not only of the
enormous depths and great extent of the oceans, and of the
circumstance that the deposits now forming in them are
distinct from anything found upon the land surface, but also
owing to the supposed extraordinary fact that the countless
islands scattered over their whole area (with one or two ex-
ceptions) never contain any Palaeozoic or Secondary rocks,
that is, have not preserved any fragments of ancient con-
tinents, nor of the deposits which must have resulted from
their denudation during the whole period of their existence!
The exceptions alluded to by Dr. Wallace* are New Zealand
and the Seychelles islands, both situated near to continents
and, according to the same writer, not really oceanic. ‘The
‘vast areas of the Atlantic, Pacific, Indian and Southern
Oceans are thus left almost without a solitary relict of the
great islands or continents which some naturalists believe to
have sunk beneath the waves of these oceans.’’ Thus writes
Dr. Wallace. Another argument in favour of the permanence
of ocean basins has recently been brought forward by Pro-
fessor Joly.+ Itis based on the facts of solvent denudation.
He regards the sodium in the ocean as the key to the history
of solvent denudation, arguing that it was derived from the
igneous rocks of the earth by the processes of weathering and
solution progressing throughout geological time. He shows
that the quantity of oceanic sodium agrees with the sediments

* Wallace, A. R., “ Island Life,” p. 105.
+ Joly, J., ‘ Radioactivity and Geology,” pp. 127—131.

Tt 2

276 ORIGIN OF LIFE IN AMERICA

as we find them upon the existing continents, and concludes
that there cannot be yet other continents with their own
burdens of sediment hidden beneath the ocean. That former
continents of any antiquity or magnitude are not hidden
beneath the waves, says Professor Joly, seems certain,
unless the estimates of sediments are quite erroneous.
Whether the estimates are correct is a question which must
be left to authorities in physical chemistry; but it has been -
argued by Professor Carthaus* that the waters of the
ocean, as well as those of continents, were originally rich in
sodium chloride, and that fresh-water organisms only came
into existence comparatively recently, that is to say in late
Mesozoic times. When we consider the enormous area of
North America that was under water in Cretaceous times for
instance, less than an equivalent strip of land in the shape of a
trans-Atlantic land bridge would be all that is required for our
purpose. We need not call it a continent.

As for the arguments in favour of the permanence of con-
tinents and ocean basins raised by Sir Archibald Geikie and
Dr. ‘Wallace, they are based on the following facts and
assumptions, viz., great ocean depths, absence of abysmal
rocks on present land surfaces, and absence of older Mesozoic
or Palaeozoic rocks (with one or two exceptions) on oceanic
islands. It has been shown, however, by Professor Suess that
great depressions on the surface of the earth’s crust are not
necessarily old or permanent. Quite near the south-west
coast of Asia Minor, and close to the mighty Ak Dagh (10,000.
feet high), a depth of over 10,000 feet has been recorded. This
depth is all the more remarkable ‘when we consider that fresh-
water Pliocene beds of the mainland are continued across to
the neighbouring island of Rhodes, thus showing that the
latter was, until such a recent geological period as the Plio-
cene, still joined to the continent. Altogether Professor
Suess} inclines to the view that geological evidence does not
prove, nor even point to a permanence of the great depths,
at least in the oceans of the Atlantic type. The next point
which has been raised in favour of the view of the permanence

* Carthaus, E., ‘‘ Klimatische Verhiltnisse der Geologischen Vorzeit.’’
+ Suess, E., “ Are Great Ocean Depths Permanent?” pp. 182—186.

SE ae

tere

~

PERMANENCE OF OCEAN BASINS O77

of oceans and continents is the supposed absence of abysmal
deposits on any existing land surface. The discovery, how-
ever, of true deep-sea ooze in Barbados and Cuba shows that .
this argument is no longer valid.* There only remains one
other argument in favour of this theory, and that is the
structure of the oceanic islands. With two exceptions, re-
marks Dr. Wallace, they do not contain any Mesozoic or
Palaeozoic rocks, being mostly volcanic. Hence he concludes
that these islands must be of modern origin. How illusive
this conception is may be gathered from Dr. Blanford’s + re-
marks on this subject: ‘If Africa, south of the Atlas, sub-
sided 2,000 fathoms, what would remain above water? So
far as our present knowledge goes, the remaining islands
would consist of four voleanic peaks, the Camaroons, Mount
Kenia, Kilimanjaro, and Stanley’s last discovery, Ruwenzori,
together with an island, or more than one, containing part of
the Abyssinian tableland, which, like the others, would be
composed of volcanic rocks, but, unlike them, would consist of
horizontal or nearly horizontal lava flows, probably of
of Mesozoic age. In southern Africa, too, the peaks of the
Stormberg and Drakensberg, though not rising, or scarcely
rising above 10,000 feet, are the highest in the country and
consist of volcanic rocks. The same is the case with the
highest peaks in Madagascar, in Mexico, in the Caucasus, in
the Elbruz chain south of the Caspian, and in many other
parts of the world; though the case of Africa is perhaps
the most remarkable.”

The question whether all the numerous oceanic islands that
are scattered about the Pacific and Atlantic Oceans are really
modern volcanic products or of recent organic origin, has
also received some attention recently. According to Dr.
Arldt,{ Archaean rocks have been noticed on the Solomon
islands, gneiss and allied rocks occur on the New Hebrides
and New Caledonia, while even from the Marquesas have
been recorded ancient rocks.

So far I have discussed only a very small portion of the
purely zoological aspect of the trans-Atlantic land connection

* Gregory, J. W., “Geology of the West Indies,” p. 307.

+ Blanford, W. T., ‘“‘ Anniversary Address,”’ pp. 34—35.
{ Arldt, Th., “ Entwicklung der Kontinente,”’ pp. 457—48.

278 ORIGIN OF LIFE IN AMERICA |

problem. This problem has been approached from many
other points of view. On the evidence of the fossil marine
mollusks of the West Indian and the Mediterranean regions,
Mr. Guppy* concluded that a migration must have taken place
right, across the Atlantic along an ancient shore-line. More
recently, Professor Gregory} dwelt upon the intimate affini-
ties that exist between the fossil sea-urchins of the West
Indian and Mediterranean areas, and urged that it could only
be explained by the assumption of a belt of shallow water
across the Central Atlantic in, at latest, Miocene times. A
few years later he adduced evidence from the fossil corals of
Barbados, that the West Indian fauna is only a fragment
of that of the Mediterranean Miocene, having received
nothing from the Pacific. That this fauna did not follow
along the shores of the North Atlantic basin is shown
by its absence from the northern Miocene of Europe and
America.{ Mr. Guppy§ has lately renewed the discussion of
this subject and once more affirmed his adherence to the
theory he expressed long ago, which has meanwhile received
so much additional support. Even the recent marine fauna of
the Antilles is intimately related to that of the Mediterranean.
Some of the faunistic marine affinities between the two re-
gions referred to might just as well have been produced by a
dispersal along a land bridge between Africa and South
America. Such, for instance, is the occurrence in early Ter-
tiary deposits of the aquatic snake Pterosphenus in Egypt
and Alabama. Dr. Andrews,|| indeed, thought it yielded an
argument in favour of the more southern land connection.

~ Let us now examine what light the recent marine mammals
inhabiting the Caribbean Sea and the Gulf of Mexico throw on
the problem. On the south-east coast of Florida we meet with
one of the most curious of American mammals. With
its seal-like head and flattened tail it is at once recognised as
something quite distinct from other marine creatures. The

* Guppy, R. J. L., ‘* West Indian Geology,” p. 501.

+ Gregory, J. W., “ American and European Echinoid faunas,”
pp. 101—108.

¢t Gregory, J. W., “ Geology of the West Indies,” p. 307.

§ Guppy, R. J. L., “ Geological Connexions of the Caribbean Region.”

|| Andrews, C. W., “ Tertiary Vertebrates of the Fayum,” p. xxv.

MARINE MAMMALS 279

manatee (Trichechus manatus), as it is called, does not in-
habit the open ocean. It frequents shallow bays and lagoons,
where it browses peaceably on seaweeds, just as cattle graze
on land. This northern manatee lives also near the coasts
of Cuba, Haiti, Jamaica and other islands, as well as along the
shores of Central America and northern and eastern South
America. Curiously enough, a second species (Trichechus
inunguis) seems to be confined to the upper reaches of the
Orinoco and the river Amazon. Still more remarkable is
the fact that a third species (Trichechus senegalensis) is
confined to the coasts and rivers of West Africa, for
since the open. ocean is to the manatees just as much
a barrier to migration as it is to terrestrial mammals, the
distribution of these manatees implies the existence of a
former shore-line across the Atlantic. It is quite true that /
in early Tertiary times manatees have lived much further
north than they do now, but the European ones, at any rate,
belonged to different genera from those now living. We
possess no evidence, therefore, for the supposition that the
ancestors of the American species passed along the eastern
shores of North America and crossed to northern Hurope
along the ancient Greenland-Iceland land bridge, thus even-
tually reaching Africa. Another theory, even less probable
I think, is that suggested by Professor Osborn.* He thought
a migration might have taken place from Africa by way of
the Pacific coasts of Asia and North America, the ancestors
of the West Indian manatees entering the Atlantic through a
strait, which is supposed to have connected that ocean with
the Pacific, in mid-Tertiary times. He considers this cir-
cuitous route a more probable one than the trans-Atlantic one.
Yet he does not clearly explain how the close relationship
between the West African and eastern South American forms
was brought about.

This, however, by no mean completes all the evidence de-
rived from the manatees in favour of the theory of a trans-
Atlantic land bridge. Dr. Dilg + has pointed out that the
molar teeth of the adult living manatees resemble those of

* Osborn, H. F., “ Age of Mammals,” pp. 4983—494.
+ Dilg, Carl, “ Morphologie des Schidels bei Manatus,”’ p. 189.

280 ORIGIN OF LIFE IN AMERICA

the Hocene Prorastomus, which must be looked upon as the
ancestor of Trichechus. I mentioned before that- Proras-
tomus has been discovered in the Eocene of Jamaica. The
teeth of another form (Prorastomus veronensis) are known:
from Italy. Thus the affinity still existing between the South
American and West African forms was apparently fore-

_ shadowed already during the Eocene Period by the relation-
_ ship of the two species of Prorastomus, the ancestors of the.

es

modern manantees. Dr. Smith Woodward, however, informs
me that the relationship of these species is too uncertain to be
used as evidence in favour of an Hocene land bridge.

All the seals inhabiting the North Atlantic, both on the
European and North American side, belong to the genera
Halichoerus or Phoca. As soon as we enter the Antillean
region these genera disappear, their place being taken by the
genus Monachus. On the opposite shores of Hurope it is just |
the same. As far south as Portugal we still find the common
seals, but as we enter the Mediterranean we again meet with
the same genus Monachus. The Antillean form (Monachus
tropicalis), like the Mediterranean Monachus albiventer,
seems to be on the verge of extinction. The former was once
common off Florida and near most of the islands. Now it is
only noticeable in the neighbourhood of Cuba and some of the
islands near Yucatan. We can hardly believe, remarked
Messrs. Sclater,* that these creatures could easily traverse
the whole Atlantic. The hypothesis of a former barrier of
land between Africa and America, which we know to be sup-
ported by other facts of distribution, would alone explain the
difficulty, according to these authors. They only had the sup-
posed land connection between Africa and South America in
mind, but what strengthens the evidence in support of another
more northerly mid-Atlantic land bridge between the Antilles
and the Mediterranean region is the fact that the only locali-
ties outside the Mediterranean where Monachus albiventer
occurs are on the coasts of Madeira and the Canary islands.

Among the terrestrial species of vertebrates and inverte-
brates of the Antilles, as I observed, the affinity with Europe
is less marked perhaps than it is in the south-western States

* Sclater, W. L., and P. L. Sclater, “ Geographyiof Mammals,” p. 217.

}f
a
er
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al
=
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>,
4

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Fig. 14.—Map of North and South America, indicating roughly the supposed
conditions of land and water about the commencement of the Tertiary Era.
The ancient land is slightly tinted.

[ To face p. 280.

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MID-ATLANTIC LAND BRIDGE 281

of North America. I explained this by the supposition that
the widespread submergence of the Antilles destroyed most of
the immigrants from Europe. It ought not to have affected
the emigrants to Europe from the Antilles to the same extent,
I mean those forms which spread from the Antillean centre,
because they would have had more time to adapt themselves
to the more elevated regions in the West Indies, and would
thus have had more chance of surviving the submergence
which did not entirely cover the islands.

One of the most noteworthy examples of that kind, though
not a very conspicuous one, is the newt Spelerpes. [ alluded
to its range in North America on several occasions (pp.187—
138 and p. 221), pointing out that its headquarters were in
Mexico, while a single species had succeeded in reaching the
Mediterranean region. We may assume, therefore, that
certain members of the old American Spelerpes stock
emigrated, in early Tertiary or even in Mesozoic times, by
means of the trans-Atlantic land bridge, that extended from
the Antilles to a land area which covered part of the western.
Mediterranean (Fig. 14). That Spelerpes long ago existed all
over the Antilles is indicated by the fact that a single species
(Spelerpes infuscatus) still inhabits the island of Haiti.

Another instance I alluded to (p. 178) in support of
the mid-Atlantic land bridge theory, is the glass-snake
family (Anguidae). The genus Ophisaurus, which is found
in the Mediterranean region, does not occur on the Antilles,
but several species are known from the mainland of North
America, The genus Anguis is quite confined to Europe,
western Asia and north Africa. On the other hand, numerous
relations live in the West Indies. Sauresia and Panolopus are
confined to Haiti, whereas Celestus (Diploglossus) inhabits
Portorico, Haiti, Jamaica, Cuba, Central America, Mexico
and northern South America. The headquarters of the
Anguidae certainly are in the West Indies and Central
America, and it is from there that they must have spread to
Europe and beyond, as far as the Himalayas, when a land
bridge across the Atlantic permitted them to do so. |

Let us now return to the investigation of the geological
history of the Antillean area. Among the vertebrates, the
mammals perhaps are of the greatest importance, in so far

a

282 ORIGIN OF LIFE IN AMERICA

as they are not supposed to be subject to accidental dispersal.
The West Indian mammals * consist of a mixture of exceed-
ingly ancient and of apparently much more modern types, and
yet all are distinct enough from mainland forms:to exclude the
idea of recent land connections of the Greater Antilles either
with Central America or the two neighbouring continents.

The most ancient mammal found in the West Indian
islands is the curious insectivore Solenodon. It is the sole
genus of the family Solenodontidae, whose nearest living
relations are the Centetidae of Madagascar and West Africa.
The two Antillean forms (S. paradoxus and S. cubanus) + are
in general quite similar. Yet they differ somewhat in size,
colour and dentition, as well as in the shape of the skull, and
for that reason are perfectly, distinct species. The first is con-
fined to Haiti, the other to Cuba. Professor Leche ¢ expresses
_ the view that Madagascar lost its continental land connection
already during the Kocene Period. Hence the Centetidae may
be of early Tertiary or even Mesozoic age. Professor Leche
believes in a former land connection between Madagascar and
Africa, and in another between Africa and Brazil. Both of
these must have existed about the same time, and they were
used presumably by the ancestors of the Centetidae and
Solenodontidae in passing from Madagascar to South
America, and thence to the West Indies, or vice versa.

The only large West Indian mammals, Capromys and
Plagiodontia, belong to the rodents. The hutias, as they are
called, remind us somewhat of the great rat-like South
American coypu, but the tail is longer and they possess
arboreal habits and certain structural characters differing
from the latter. The two genera of hutia are quite confined
to the West Indies. Three species of Capromys are known
from Cuba, one from the Bahamas and one from Jamaica.
Still another Capromys inhabits the small Swan island, in the ~
Gulf of Honduras, mid-way between Jamaica and Central
America. Nevertheless, the genus is quite unknown from the
mainland, ‘The other genus (Plagiodontia) only occurs on

* Allen, Glover M., ‘‘Mammals of West Indies.” (This work was
received too late for discussion. )

+ Allen, J. A., “Notes on Solenodon paradoxus,” pp. 507-—515.
{ Leche, W., “ Centetidae, Solenodontidae, &c.,”’ pp. 132—139.

MAMMALS OF WEST INDIES 283

Haiti. Of the past history of these hutias we only know
that one extinct species (Capromys columbianus) has been
discovered in the Pleistocene deposits of Cuba. The only near
relation living is Procapromys geayi, from the neighbourhood
of Caracas in the mountains of Venezuela. This implies
southern affinities of the genera Capromys and Plagiodontia.
Proceeding further south in search of their possible ances-
tors we meet with another nearly related genus (Matyoscor)
in the Pleistocene of Bolivia. Still further south we find
on some of the islands of the Chilean coast, as well as in Chile,
Peru and Argentina, the coypu (Myocastor coypus), already
alluded to as resembling the hutias. Finally, in the Pliocene,
Miocene and Eocene beds of Patagonia, various ancestral
types of these modern forms have been discovered by Pro-
fessor Ameghino. Thus the available evidence points to a
remote Patagonian origin of the hutias. The question then
arises, have the ancestors of these West Indian mammals
proceeded northward through eastern or western South
America ? The testimony we possess is distinctly in favour
of the latter theory, though it is mainly of a negative cha-
racter. In the west we have the living coypu and the extinct
Matyoscor, while the former has only invaded Brazil in recent
geological times. The Venezuelan Procapromys might lead
us to believe that the ancestors of the hutias had gained
admittance to the Antillean region by an old land connection
across the lesser Antilles. But since no trace of the former
presence there of any coypu-like mammal has been dis-
covered, and as a species of hutia exists on Swan island, the
hypothesis that the ancestors of these mammals reached the
West Indies directly from some western lands seems to me the
most probable.

Except the Bahama raccoon (p. 181) and a species of
opossum (Didelphys marsupialis), which inhabits the islands )
of Trinidad, Dominica, Grenada and St. Vincent, all other
Antillean mammals are small and inconspicuous. The
raccoon may possibly be very ancient, but we know too little
about its geological history to enable us to speculate on
its origin in the Bahama islands. The presence of the
opossum on some of the Lesser Antilles seems to indicate
that they had been connected with one another and with Vene-

Pero ger atte tm F 3 ee > a
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RAI PEEL OTE IE

284 ORIGIN OF LIFE IN AMERICA

zuela within comparatively recent geological times, a con-
clusion which perfectly agrees with the results obtained from
other faunistic evidence.

The groups of smaller mammals which have representa-
tives in the West Indies are the rice-rats (Oryzomys) and |
the musk-bearing rats (Moschophoromys=Megalomys). Like
the hutias and solenodons, the latter are confined to this
region, but they are only known from the Lesser Antilles,
Moschophoromys desmaresti being peculiar to Martinique,
whereas M. luciae is only found on St. Lucia. The occurrence
of this peculiar genus of small mammals on the Lesser
Antilles implies that their connection with the mainland must
be of longer standing than is generally supposed. The
opossum (Didelphys marsupialis), is one of the few species
of terrestrial mammals having a wide range in both North
and South America, and must, therefore, be considered as
a persistent specific type of great antiquity. It may possibly
have retained its specific characters, while the ancestors of
the musk-bearing rats rapidly became modified on the islands.
That the latter are not recent introductions is likewise in-
dicated by the fact that an extinct species of Moschophoromys
is known from Barbados.

The rice-rats (Oryzomys) inhabit both the islands and the
mainland. Their very wide and discontinuous range in North
and South America at once suggests an ancient origin. One
species (OQ. antillarum) was so abundant in Jamaica, and did
such damage to the crops, that the mongoose, a small carni-
vore, was imported from India for its destruction. For a
time the experiment appeared to be quite successful. After
some ten years, however, when the rice-rats became scarce,

) the mongoose began to pay attention to snakes, lizards,
tortoises and birds. As it developed a taste for them they
in their turn became scarce, until it was found that
the mongoose was worse than any other animal pest, for,
owing to the great destruction of the useful members of

| the fauna, insects and ticks had increased to an alarming
| extent. The disturbance of the due balance of nature by
man is always risky, and thus sometimes leads to incalculable

: | damage.
A second species of rice-rat (O. victus) is peculiar to the

|

FOSSIL MAMMALS OF WEST INDIES 285

Lesser Antilles. A few others live in Trinidad. It is im-
probable that Jamaica was at any time connected by land
with the Lesser Antilles, independently of the larger islands.
It is possible, therefore, that the genus, being mainly South
and Central American, entered the Antilles in two independent
streams, one from the south, the other from the west. This
may have taken place when the other large islands had already
become isolated from Jamaica.

We have still to consider the remains of some extinct
mammals which ‘have been traced in the Antilles. To judge
from recent cave researches in Cuba, we are only now begin-
ning to acquire a knowledge of the past history of this fauna,
though certain indications enable us to speculate as to its
general nature and origin. Dr. Spencer * alludes to the dis-
covery in a Cuban cave of large edentate remains belong-
ing to Myomorphus cubensis. This creature, which Dr.
Matthew informs me is now known as Megalocnus, was about
the size of a small bear, being a peculiar aberrant specializa-
tion apparently derived from some Miocene (Santa Cruz)
ground sloth. Professor Ameghino + describes a new species
of man (Homo cubensis) from a cave in Cuba; and from a
preliminary report read at the International Congress of
Geology at Stockholm by Professor de la Torre, we are led to
infer that other edentates, and also several kinds of rodents,
lived on this island within comparatively recent geological
times. Dr. Matthew writes to me that the mammalian re-
mains from Cuba sent to the American Museum of New York
are awaiting determination. Dr. Spencer { also makes refer-
ence to several large species of rodents of the genus Amblyr-
hiza which were found in the phosphate beds of the small
island of Anguilla. The Amblyrhiza remains are now thought
to belong to a single species (A. inundata), closely related to
Castoroides, a giant beaver, which made its first appearance
in North America during the Pleistocene Period. The former
presence in Anguilla and Cuba of large mammals naturally
suggests that these islands had some continental connection.
Dr. Spencer, indeed, quotes these fossils in support of the

* Spencer, J. W., “ Antillean Continent,” pp. 128—138.

+ Ameghino, FIL. “ Nueva especie del género Homo,” p. 5.
t Spencer, J. W., “ Fossil Mammals in Cuba,” pp. 512—513.

286 ORIGIN OF LIFE IN AMERICA

theory, largely based on the supposed drowned valleys of the
Antillean area, that the two American continents were united
with one another by means of a West Indian land bridge
during the Pleistocene Period. He thought this land must
have had the enormous altitude of from 8,000 to 12,000 feet.
Against this view it may be urged from a general faunistic
study that such a land bridge is out of the question,
because the Antillean fauna would be quite different from
what it actually is. A very small part of southern Florida
may have been still joined, by way of the Bahamas, to Cuba
and Anguilla in Pliocene times. But southern Florida must
then have been separated from North America by a marine
channel. Nor could there have been any junction of the
greater Antillean land with South America, by means of the
Lesser Antilles, at any time during the Tertiary Era. In all
probability the West Indies, while still partly united with one
another, had some kind of land connection with Central
America, while the latter was cut off by the sea from both
North and South America. Hence the mammalian supply came
mostly from the west. Still, it may be asked, how did this
fauna reach Central America ? Almost all the Antillean mam-
mals, both recent and extinct, can be traced to a southern
ancestry, except Castoroides, of which we only know that it
appeared in the north along with a host of southern invaders.
I believe the cause of the mystery connected with the occa-
sional entrance during various periods in Tertiary times of
South American forms into North America is now buried
beneath the waves far out in the Pacific Ocean (see Fig. 14).
I have frequently suggested the theory that a large land
surface, mainly tenanted by a South American stock, lay
westward of Central America. A good deal of the next
chapter will be devoted to its consideration. Meanwhile,
I can only state my conviction that the animals alluded to,
and many others, had their origin on that western Pacific
land whence they streamed into the neighbouring continents
whenever physical conditions offered an opportunity for
doing so.

The main conclusion which this brief study of the mam-
malian fauna of the Antilles has revealed is that the larger
islands were formerly united with one another, and with the

ELEVATION OF WEST INDIAN AREA 287

Bahamas, by land. How far eastward this land extended
cannot be determined from the mammals, but it certainly
must have reached beyond the Virgin islands to Anguilla, one
of the most northerly islands of the Lesser Antilles. Many
islands of the Lesser Antilles may have been completely
submerged at that time. Later on Cuba, the Bahamas and
Jamaica were connected with the mainland, after the other
islands had already been separated from the Antillean land-
mass, and lastly, Cuba and Jamaica were independently joined
to Central America before the existing physical features were
brought about.

Many more details are required before we can construct
an approximate history of the geological events which led to
the present conditions of the fauna and flora of the Antilles.
In his chapter on the evolution of middle America Dr.
Gadow * deals with the problem from the aspect of the
reptilian and amphibian fauna. He does not attempt.to recon-

_ struct the geological history from a study of this fauna alone.

His maps are derived and abstracted from the opinions ex-
pressed by various geological authorities. They are in so far
of importance, as he thinks, that the general conclusions
based on a geological study appear to fit those founded on
faunistic considerations. Several striking points may be
gathered at a glance from his maps. At no time since the
Cretaceous Period were the Antilles directly connected with
the main continent of North America. Only in Miocene times
was ‘“ Antillea’’ (the term used for the united Antilles) joined
to southern Florida, the latter being then disconnected from
North America. Antillea had only one continental connec-
tion, namely, during the Miocene Period by means of Central
America. It follows, therefore, that Antillea never was directly
joined either to North or South America, at least not since
Cretaceous times. If Dr. Gadow’s maps are correct, the whole
of the Antillean fauna and flora, in so far as they are derived
from migration on land, should be of Miocene age or older.
Dr. Gadow’s conclusions would have been of greater value had
he trusted more to the evidence based on geographical dis-
tribution and less on that of geology. As pointed out by

* Gadow, H., “ Mexican Amphibians and Reptiles,’ pp. 284—237,

..

288 ORIGIN OF LIFE IN AMERICA

Dr. Stejneger,* a few Antillean genera, such as Ameiva,
Amphisbaena, Typhlops and Alsophis, possess a southern rela-

, tionship. The species of burrowing snake, Typhlops lumbri-

calis, is even confined to the West Indies and British Guiana
without entering Central America. Dr. Stejneger does not
actually speak of a former land connection of Antillea with
South America, but I explained above that some geologists
advocate an ancient union of the two continents by way of
the Lesser Antilles. If such a connection existed, I think
it must have been in the pre-Cretaceous times. Most zoo-
logists would deride the idea of any terrestrial species
having been transmitted to us unchanged from pre-Cretaceous
times to the present day. We have no geological evidence of
such a fact, but Dr. Sarasin expresses the opinion that the

f genus Typhlops, at any rate, is older than the Cretaceous

Period. We gather from Dr. Stejneger’s researches that the
great majority of the Portorican species are western in their
affinities, and that Portorico and the more easterly Virgin
islands certainly must have been connected with one another
in comparatively recent geological times.

As regards Jamaica, Mr. Barbour gives us some interesting
details as to its reptiles and amphibians. He emphasises the
fact, which I have already alluded to in speaking of the
mammals (p. 285), that the distinctive characters of this
island are not shared by the rest of the Antilles. Jamaica is
related faunistically to Central America and Haiti, while the
relationship with Cuba is much more remote. Mr. Barbour
thinks that the early separation of Jamaica from the main-
land and from Haiti would account for the absence of types
having such a distribution as Bufo and Amphisbaena, which
may have reached Haiti from Central America by way of
Cuba. If fortuitous dispersal has played practically no part in
providing the Antilles with a fauna, as Mr. Barbour? is in-
clined to think, the Bahamas certainly must have belonged to
Antillea and cannot have been submerged since. Sixteen
species of reptiles and amphibians are described by Mr.
Barbourt as occurring in the Bahaman archipelago. Several

* Stejneger, L., “ Herpetology of Porto Rico,” pp. 561—3563.

+ Barbour, Thomas, “ Herpetology of Jamaica.” pp. 277-—285.

¢{ Barbour, Thomas, “ Batrachia and Reptilia of Bahamas.”

— Ee oe ee eee

ANCIENT LAND CONNECTIONS 289

of these are peculiar to the group. And yet in spite of this
feature, in spite of the fact that two kinds of mammals live on
the islands, and that numerous mollusks and other inverte-
brates are quite confined to the Bahamas, we often read the
statement that the fauna of these islands is entirely a product
of accidental transport by winds, waves or human agency.

How little influenced the Antilles are by accidental intro-
ductions is well shown by a study of such groups as the
dragon-flies and their allies (Neuroptera and Pseudoneu-
roptera), and the butterflies and moths (Lepidoptera). If
winds played any active part in their dispersal, we should
find many species from, North America in the Greater Antilles,
whereas the affinities agree almost precisely with those of
the other animals already considered. Several genera of
dragon-flies, known both ‘from North and South America, such
as Chauliodes, Corydalis, Mantispa and others, are wanting
in the West Indian islands, thus showing that the migration
between the two continents did not take place across the
Antillean area. The great majority of the genera are South
or Central American. Only two genera of dragon-flies are con-
fined to the Antilles. On the other hand, many continental
ones are absent. The Lesser Antilles contain some South
American species which are wanting in the Greater Antilles.*
Similarly the Lepidoptera exhibit affinities with northern
South America, Central America and Florida. Several cha-
racteristically southern families, nevertheless, are wanting in
the Antilles. The four large islands are characterised by the
absence of many neotropical genera, and the presence of a
genus and many species that are peculiar to them. Jamaica.
shows some special features of interest.}

The birds exhibit similar peculiarities in their geographical
distribution. One whole family, the todies (Toditae), are con-
fined to the larger islands of Cuba, Jamaica, Haiti and Por-
torico. They bear a certain resemblance to the kingfishers,
but differ in colour, whereas in habits and shape of bill they
resemble the flycatchers. In reality they are related to the
Central American motmots. We also have the same striking

* Kolbe, H. J., “ Neuroptera und Pseudoneuroptera d. Antillen,”
pp. 154—161.

+ Pagenstecher, A., “ Verbreitung der Schmetterlinge,” pp. 391—394.

L.A. U

290 ORIGIN OF LIFE IN AMERICA

number of absentees and peculiar species among the birds,
as in other groups. Dr. Chapman* is evidently puzzled how
to account for the avifauna. Nevertheless, he makes the
remarkably suggestive statement that if it could be shown
that Central America was cut off from both continents at the
time when it was joined to the West Indies, the origin of the
island fauna could be explained in a satisfactory manner.
That is precisely, I think, what did happen, as I have indicated
above.

Cuba presents some special aspects of interest. We have in
the first instance quite a remarkable assemblage of fossil
mammals. Western Cuba, with its extensive limestone dis-
tricts, abounds in caves, many of which contain stagnant
water or running streams. One of the most remarkable fea-
tures of these subterranean waters is that they are tenanted
, by two kinds of fishes belonging curiously enough to a family
of deep-sea forms (Brotulidae). These species, Stygicola
dentatus and Lucifuga subterraneus, moreover, are blind,
as might be expected from their habitat. Another typically
marine genus, Atherina, possesses a single fresh-water species
(A. evermanni) which is only known from western Cuba.
Whether the presence of these marine species in fresh water
implies that western Cuba had been submerged below sea-
level is a debatable question that need not be further pur-
sued. Other Cuban fresh-water fishes are forms often found
in brackish water, or marine forms migrating into fresh water.
Besides these there are two species of Heros, a Symbranchus,
a Lepidosteus and one Agonostomus, all of which belong to ©
purely fresh-water groups that could only have reached Cuba
by means of a continuous system of lakes and rivers between
the mainland and the island. Heros tetracanthus and Heros
nigricans are members of the family Cichlidae, which has a
wide range in South and Central America, only a single
species entering the United States. Agonostomus monticola
has a wider distribution in the West Indies, and is also met
with in Mexico. Lepidosteus tristoechus lives in Mexico and
the southern States, while Symbranchus marmoratus is widely
distributed in the fresh waters of tropical America. If, as

.* Chapman, F. M., “ West Indian Bird Life,” p. 330.

BLIND ANIMALS IN CUBA 291

geologists claim, western Cuba has been deeply submerged, it
seems equally certain that it must have been subsequently
joined to Central America. As Professor EHigenmann* re-
marks, this Cuban fauna has greater affinity with that of
Mexico than with that of Florida, showing that the fishes
probably reached Cuba by way of Yucatan.

Western Cuba possesses, among other curiosities, blind
crustaceans (Palaemonetes). They are what we might call
monster prawns, and have probably had marine ancestors.
An allied species is known from the subterranean waters of
Texas. Faunistically they are not of great importance. Not
so, however, the fresh-water crayfishes, which are justly
regarded by Dr. Ortmann + as among the most valuable means
for demonstrating former changes of land and water. All the
species of Cambarus but one inhabit either Mexico or the
United States. Only a single crayfish occurs in the isolated
position of Cuba. This species (C. cubensis) is closely related
to Cambarus mexicanus, whereas the United States species are
more distant relatives. Dr. Ortmann assumes on that
account a former land connection between Mexico and Cuba.

The fresh-water crabs, as I already indicated, advanced
northward from the south, eventually invading the Central
American territory and the West Indies. Thus three species
of Pseudothelphusa have been discovered in Cuba. One of
these (P. americana) ranges from Mexico through Cuba to
Haiti. Another (P. terrestris) is confined to Mexico and
Cuba, while a third (P. affinis) is restricted to Cuba. More-
over the genus Epilobocera is peculiar to the Greater
Antilles, viz., Cuba, Haiti and Portorico, and some smaller
neighbouring islands. A species of Pseudothelphusa closely
allied to a Venezuelan form is likewise known from some of
the Lesser Antilles.

From these facts Dr. Ortmann (pp. 844—3847) concludes
that the first immigration of fresh-water decapods represented
by Epilobocera, into the Greater Antilles, belongs to the end
of the Cretaceous or the beginning of the Tertiary era.
Cambarus cubensis, he suggests, possibly belongs to it also.

* Higenmann, C. H., “ Freshwater Fishes of Cuba,” pp. 220—221.
+ Ortmann, A. E., “ Distribution of Freshwater Decapods,”’ p. 316.

u 2

292 ORIGIN OF LIFE IN AMERICA

Although it is a primitive form, he prefers to put its immigra-
tion in the Tertiary rather than in the Cretaceous. Tihe history
and development of the Central American and West Indian
region he imagines to have been as follows: “‘ Central America,
the West Indies and the northern margin of South America,
formed in the Mesozoic Period (certainly during the Jurassic
and Cretaceous) a continental mass (Antillean Continent),
which was bounded by sea to the north and south (Fig. 15).

This continent broke up at the end of the Cretaceous,
the chief factor in its destruction being the formation
of the Caribbean Sea. The northern remnant of this
continent, consisting of the Greater Antilles and parts
of the present Central America, probably remained a unit
up to the Eocene.” At the end of the LHocene, he
continues, and during the Oligocene and Miocene Periods,
the connection between the Greater Antilles and the main-
land was severed, being subsequently re-established toward
the end of the Tertiary Era (Fig. 20) and again destroyed in
recent times.

My own views are in some respects similar to those of Dr.
Ortmann, yet they differ in a few important points. If we
begin, say with later Cretaceous times, when a wide marine
channel still separated eastern from western North America,
northern South America was submerged, and could not have
formed part of the supposed Antillean Continent. Towards
the end of the Cretaceous Period, all the Antilles, except the
Bahamas, were entirely covered by the sea, according to Pro-
fessor Schuchert’s paleogeographic maps (Map 95). Yet
although the peninsula of Yucatan was then submerged, no
deposits of this age are known from Guatemala or Honduras,
nor have any Mesozoic or Tertiary beds been discovered in
these countries. The North American relationship of the
relict fauna inhabiting these countries indicates that they
were connected by land with western Mexico. I shall also
show later on that this region was united by land with western
South America before the Isthmus of Panama came into exis-
tence. Possibly the Greater Antilles were not so completely
covered by the sea as is assumed. They may have been repre-
sented by small islands, and these would have possessed frag-
ments of an ancient fauna and flora. Cuba, at any rate,

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, ie ee te

ANCIENT ANTILLEAN CONTINENT 298

emerged at the beginning of the Tertiary Era, and must then
have been joined by land with Mexico. Some time during
the Oligocene Period Professor Schuchert again records a
complete submergence of all the West Indian islands except
the Bahamas. But such ancient types as Typhlops, Soleno-
don and many others, could not have been destroyed. We
might suppose that they took refuge on the Bahamas, and
thus repopulated the other islands subsequently. Such a
theory, however, is exceedingly unlikely. A much more pro-
bable explanation is that the Antilles were reduced to small
islands, and retained their old animals and plants. In early
Miocene times all the Greater Antilles were certainly raised
above the sea, and must have been then connected with one
another. Jamaica was joined to Guatemala, and Cuba to
Mexico, but Jamaica must have separated early from Haiti.
While the islands were joined to one another, an interming-
ling of the more active ancient types occurred, the less pro-
gressive ones being forced to the higher altitudes by the new
arrivals from Mexico and Central America. During the whole
of Miocene times Yucatan was apparently below sea-level.
When it rose in the Pliocene Period, it may have had a short
land connection with the Antilles by way of western Cuba.
An opportunity was then afforded the mammals of South
American type like Amblyrhiza, Megalocnus, and others to
spread to the islands. The smaller West Indian mammals
came earlier. Central America, during the existence of this
Yucatan land bridge, may still have been separated from
North and South America. At this time the Lesser Antilles
probably had an independent land connection with Venezuela; /
but that there was an Antillean Continent connected with the
mainland in Pleistocene times, as suggested by Dr. Spencer,
when Central America had already been invaded by the North
and South American immigrants, is entirely opposed to the
results derived from a study of the fauna and flora.

As for the trans-Atlantic land bridge, we cannot assume
that it oscillated up and down like the Antillean area, where
peculiar local conditions produced exceptional changes of land
and water. Some time during the Hocene Period it must
have enabled European types to travel right across the
Antilles and whatever portions of Central America then

294 ORIGIN OF LIFE IN AMERICA

existed, to western North America. I have endeavoured to
roughly represent on a map my conception of the geographical
conditions then prevailing in North and South America
(Fig. 14). Then followed a complete cessation of the migra-
tory stream to North America. This must have corresponded
with the depression of the Antilles. During the Oligocene
Period Professor Osborn recorded a re-establishment of the
faunal resemblance of western North America with western
Kurope. Here our correlation of Antillean geology with that
of the continental mammalian deposits fails us completely.
The supposed Oligocene beds of the Antilles-may really belong
to the Eocene Period. Another phase of independent evolu-
tion then succeeded this faunal interchange with western
Kurope. This has been represented on another map (Fig. 16),
although I am fully aware of the extreme difficulties and
pitfalls connected with such an attempt. Later on, in
Miocene times, a fresh invasion occurs from the Old World.
This, I think, certainly did not come from the same quarter
as the others. We may conclude, therefore, that the land
bridge between the Antilles and Kurope ceased to exist some
time during the Oligocene Period. It is quite possible that
long after that time large islands may have marked the former
site of the land bridge, while temporary land connections be-
tween the Azores and Europe, and between the Canary islands
and Africa, may have involved certain fragments of the older
trans-Atlantic land connection.

Fic. 16.—Map of North and South America, indicating roughly the supposed
conditions of land and water about the middle of the Tertiary Era. The
ancient land is slightly tinted. e

[ To face p. 294.

fax"

CHAPTER XII

THE GALAPAGOS ISLANDS

Riext on the Equator, off the west coast of South America,
in the Pacific Ocean, lies a small group or archipelago of
islands known as the “‘ Galapagos islands.’’ There are five
large islands and twelve small ones, the most extensive
(Albemarle) being about eighty miles long and of very irre-
gular shape, while the four next in importance (Chatham,
Indefatigable, James and Narborough) are each about twenty
or thirty miles in length, and of a rounded or elongate form.
They are best seen on the map representing the range of
Helicina (Fig. 11) being situated within the circle nearest
South America. The climate of the islands is cooler than
that of any other equatorial land at sea-level, because the
temperature of the surrounding water is singularly low. This
is caused by the Humboldt current, which strikes the islands
during its north-westerly course on its way from the cold
southern regions. The lower slopes of the islands suffer from
want of rain. At a height of a thousand feet and upwards
sufficient moisture is condensed to provide for a fairly
luxuriant vegetation.

The Galapagos islands differ in two important respects from
many of the West Indian islands. They are entirely formed
of volcanic rocks, according to Mr. Darwin, who gave us the
first reliable description of them, and they are situated at the
great distance of seven hundred and fifty miles from the main-
land of South America. The nearest land, apart from the
small Cocos islands, is Ecuador, to which state the Galapagos
archipelago now belongs. In the case of the Antilles almost
all authorities are agreed that the nucleus of the fauna re-
presents survivals from the time when the islands were joined
to the mainland, and that accidental distribution has not
greatly modified the original fauna. In the Antilles we meet

296 ORIGIN OF LIFE IN AMERICA

with a number of ancient types of animals and plants. In the
Galapagos islands similar relicts of bygone ages are found, yet
their presence on the islands is not generally considered to
be due to a former land connection with the mainland. But
the question whether the animals and plants inhabiting this
archipelago are the descendants of purely accidental visitors
or not, is of more than usual importance in this case. Both
Mr. Darwin and Dr. Wallace expressed the opinion that the
Galapagos islands are of the oceanic type, and that they
originated from sub-oceanic volcanoes, having never formed
part of a continent or any large land-mass. Many of the more
recent observers have followed the lead of our two great
naturalists. I need only mention Professor Agassiz, Dr.
Wolf, Mr. Salvin, Dr. Dall and Dr. Stearns. On the other
hand, Professor Baur was the first to seriously contest the
view of these authorities. His researches led to a reconsidera-
tion of the problem presented by the fauna and flora of the
Galapagos islands and a rejection by many naturalists of the
theory so ably maintained by Darwin and his followers.

Islands, as I have already indicated, possess many advan-
tages over continental areas for the study of the laws and
phenomena of distribution. The islands we are now dealing
with, moreover, are of the most profound importance in con-
nection with the geological history of the two great American
continents. We might almost say that the problem of the
Galapagos fauna presents the key to the solution of the most
complex and intricate questions concerning the American
fauna with which we are confronted. It is for this reason
that the whole of this chapter will be devoted to an exhaustive
survey of the Galapagos islands and their inhabitants.

When Darwin landed on the archipelago in 1835, he noted
in the first instance the fact that all the islands were formed
of volcanic rock and that they contained numerous craters.
The craters he found to consist either of lava and scoriae, or
of finely-striated sandstone-like tuff. All the latter, which he
examined, had the southern sides either much lower than the
other sides, or quite broken down and removed. He concluded
from this fact that all these craters were formed beneath the
sea, and that their broken state was due to the action of the
waves produced by the southern trade winds. On the other

DARWIN ON GALAPAGOS FAUNA 297

hand, Darwin’s* remark that he noticed a few fragments of
granite curiously glazed and altered by heat among the ejecta-
menta, would seem to imply that the bases of the craters are
composed of older forms of eruptive rocks. This supposition
is strengthened by an observation made by Professor Suess,+
that on the whole of the Pacific coast of America only a single
mountain range comes to an abrupt termination on the Pacific
coast, namely, the Central American continuation of the An-
tillean Cordillera, and that precisely at the point where we
might imagine the arcuate prolongation of this chain to meet
the principal South American mountains lie the volcanic Gala-
pagos islands. At any rate, as Dr. Blanford { has pointed
out, the rocks of an island may be entirely volcanic, although
the island may nevertheless be a remnant of a continental
mass. Except that some of the craters have their southern
faces broken down, which may be due to some other cause
than that suggested by Darwin, the Galapagos islands could
just as well represent the mountain tops of sunken land as
the summits of originally submarine volcanoes. Neither of
these two theories is supported by strong geological evidence.
No one was more impressed by this fact than Darwin himself,
and he bases his theory of the origin of the Galapagos fauna
and flora almost entirely on the nature, composition and dis-
tribution of the animals and plants he found on the islands.
His conclusions were that all the animals and plants must be
derived from accidental transport by sea-currents or by birds,
except for a few recent immigrants which were introduced by
man.

The natural history of the islands, as Darwin truly remarks,
is. eminently curious and well deserves attention. Of terres-
trial mammals, he says, there is only one which must be con-
sidered as indigenous, namely a mouse (Mus galapagoensis).
A rat also is sufficiently distinct from the common kind to have
been named and described, “ but,” continues Mr. Darwin,
‘as it belongs to the Old World division of the family, and as
this island had been frequented by ships for the last hundred
and fifty years, I can hardly doubt that this rat is merely a

* Darwin, C., “ Journal of Researches,” pp. 270—271.

+ Suess, E., “ Das Antlitz der Erde,” IT., p. 263.
{ Blanford, W. T., “ Anniversary Address,” p. 34.

298 ORIGIN OF LIFE IN AMERICA

variety, produced by the new and peculiar climate, food and
soil to which it has been subjected.” Hence Darwin * con-
sidered the rat as imported by man, and he adds that the
transportation of the mouse in a vessel from the mainland
is not improbable.

Dr. Wallace coneurs with Mr. Darwin in the belief that the
Galapagos islands agree with all other oceanic islands in so
far as they are devoid of indigenous mammals. He acknow-
ledges that the mouse, which had since been found to belong
to the American genus Hesperomys, differs somewhat from
other known species. Yet he remarks that we can scarcely
consider the species to be indigenous, firstly because these
creatures have been little studied in South America, and that
there may still be many undescribed mice there, and in the
second place because even had it been introduced by some
Kuropean or native vessel, there would have been ample time
in two or three hundred years for the very different conditions
to have established a marked diversity in the characters of the
species. Dr. Wallace?+ reiterates in conclusion Darwin’s
statement that the islands are really destitute of truly in-
digenous mammals.

Now since these great naturalists wrote about the Gala-
pagos archipelago, and stated their opinions on the mam-
malian fauna of the islands, the latter have been visited by
many competent observers, who brought their collections
home for careful study. Thus the mammals collected by
Dr. Baur on the islands were described by Dr. Allen, who
recognised among them a typical brown rat (Mus decu-
manus). He also thought that a skeleton which was picked
up on South Albemarle belonged to the black rat(Mus rattus).
There was likewise a bat which he identified as closely allied
to a Chilean form, but sufficiently distinct to deserve the
separate name of Atalapha brachyotis. Dr. Allen,{ moreover,
points out that the Galapagos mouse does not belong to the
Old World genus “‘ Mus ”’ nor to “‘ Hesperomys,’”’ but agrees
with Oryzomys, the well-known American rice-rats. Besides

* Darwin, C., ‘“ Journal of Researches,” p. 275.
+ Wallace, A. R., ‘Island Life,” p. 278.
¢ Allen, J. A., “ Mammals from the Galapagos Islands.”

si Sata

ah 92 itentigeen Tey I eae i int

RATS ON GALAPAGOS ISLANDS 299

Oryzomys galapagoensis he found a second distinct form
which he named Oryzomys bauri.

A more important natural history survey of the islands
was made by the Hopkins Stanford Expedition in 1898. In
addition to the mammals already known from the archipelago,
it was discovered that Narborough, Indefatigable and Sey-
mour islands are inhabited by rice-rats, which show such
structural distinctness in the interorbital portion of the skull
that Mr. Heller * proposed their being placed into the
new genus “‘ Nesoryzomys.”’ Four mouse-like mammals are
thus known to be peculiar to the Galapagos islands, viz.,
Oryzomys galapagoensis, O. bauri, Nesoryzomys indefessus
and N. narboroughi. The only other terrestrial mammal not
found elsewhere is Atalapha or, as it is now called,
Lasiurus. brachyotis.

It is interesting to note that the genera to which these
species belong are characteristically American. Both Ory-
zomys and Lasiurus have a wide range in North and South
America as well as in the Antilles. We have learned that
Oryzomys antillarum is confined to Jamaica. Another species
lives on St. Vincent, and several more on Trinidad, while a
species (QO. nelsoni) is peculiar to the Tres Marias islands off
the west coast of Mexico. A genus ranging from New Jersey
in the north to Tierra del Fuego in South America, with a
large number of species, must be a very ancient one; and
yet not a single species occurs outside the New World.

I have never hitherto alluded to bats because they are so
generally regarded as of little value in faunistic problems.
Specialists of this group, such as Dr. Knud Andersen,y} in-
form us, however, that this assumption is by no means correct,
and that in most cases bats are as good and reliable zoogeo-
graphical guides as other small but non-flying mammals.
The fact that although Lasiurus is found from Canada to
Patagonia it has nevertheless preserved its original habitat
in the New World, and has not even crossed Bering Strait into
Asia, would seem to support Dr. Andersen’s contention, while
its antiquity is vouched for by the occurrence of distinct
species of Lasiurus on several remote American. islands.

* Heller, Edmund, “ Mammals of Galapagos Archipelago.”
+ Andersen, K., “ Geogr, Distribution of Rhinolophus,” p. 652,

300 _ ORIGIN OF LIFE IN AMERICA

Lasiurus has likewise succeeded in reaching one other group
of islands besides the Galapagos archipelago, namely the
Sandwich islands. The latter are inhabited by Lasiurus
semotus, which is peculiar to them, and cannot therefore be
considered as a recent human importation.

Our present knowledge of the mammalian fauna of the
Galapagos islands has added one factor of extreme importance
to those hitherto known, namely the certainty that there are
indigenous mammals on the archipelago. For this reason the
Galapagos islands should be excluded from the oceanic
islands, and be placed among the islands which once formed
part of a larger land-mass or continent. It is not certain,
however, that: Darwin and Wallace would have taken that. view,
even had they been convinced that the mammals alluded to
were truly indigenous in the islands. Some naturalists hold
that even mammals can be successfully transported across
the ocean on tree trunks and floating islands. Dr. Stearns,*
in alluding particularly to the Galapagos fauna, remarks
that a single tree of large size might carry with it not only
molluscan and insect life, but also living individuals of many
vertebrate forms that found refuge or safety upon it. Thus,
he continues, if the environmental conditions were at all
favourable, colonies of many animal forms could be trans-
planted to distant regions. The possibility of such an acci-
dental transportal must have been carefully considered and
rejected by Darwin and Wallace. The Humboldt current I
alluded to as striking the Galapagos islands does not come
from the coast of Ecuador nor from Central America. It
originates in the far south, and, passing northward, skirts the
coast of Chile and southern Peru, and then leaves the land ina
north-westward direction. The tree trunks spoken of by Dr.
Stearns as carriers of all kinds of animal life would have had
to travel several thousand miles, no doubt experiencing stormy
weather on the way, before they could have safely deposited
their loads of vertebrates on the shores of the Galapagos
islands. If these floating trees are responsible for the present
mammalian fauna of these islands, how is it that they have
brought nothing new to them since their occupation by man ?

* Stearns, R. E. C., ‘“ Mollusk-fauna of the Galapagos Islands,”’ p. 366,

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ACCIDENTAL DISPERSAL 301

Man has brought the brown and the black rats apparently.
Why should the agencies of accidental transport have been
so much more potent in the distant past than they are
now? We might add also, is it possible that these same
agencies should be able to select the most ancient forms of
life as more suitable for transport than more modern pro-
ductions ? Of course, these ideas of mammals being carried
across a vast expanse of ocean and safely landed on a distant
shore are mere conjectures unsupported by any evidence.

“ Of land-birds,” says Mr. Darwin, “I obtained twenty-six
kinds, all peculiar to the archipelago and found nowhere else,
with the exception of one lark-like finch (Dolichonyx oryzi-
vorus) from North America.” Of waders and water-birds he

~ succeeded in capturing eleven kinds, only three of them being

new species. In 1875 the number of land-birds known to Mr.
Salvin had increased from twenty-five to thirty-six species.
Most of the genera to which they belong are of very wide
distribution; seven, ‘however, are confined to continental
America, leaving five peculiar to the islands. Mr. Salvin *
expresses no doubts as to the correctness of Darwin’s inter-
pretation of the origin of the Galapagos islands. Hence he
concludes that the birds now found on the islands, being
related to American birds, must have emigrated from’ America
and have become modified by the different climatic condi-
tions with which they were surrounded. A later review of the
Galapagos birds was undertaken by Mr. Ridgway + in 1897,
when the number of land-birds recorded from the islands was
nearly doubled. He notes the exact distribution of the various
species and varieties in detail, and shows how circumscribed
their range is. Of the five genera peculiar to the islands
only two, viz., Nesomimus and Nesopelia are of evidently
American relationship. The remaining three, he thinks, have
so obvious a leaning towards certain Hawaiian dicaeidine
forms, that the possibility of a former land connection with
the Sandwich islands, either continuous, or by means of inter-
mediate islands as “stepping stones,” becomes a factor in
the problem of their origin. “It may be,’’ he adds, “that
the resemblance of Cocornis, Cactornis and Carnarhynchus

* Salvin, O., “ Avifauna of Galapagos Archipelago.”
+ Ridgway, R., “ Birds of Galapagos Archipelago,” p. 467.

302 ORIGIN OF LIFE IN AMERICA

to the above-mentioned Hawaiian forms, is merely a super-
ficial one, and not indicative of real relationship. Drs. Roth-
schild and Hartert, indeed, believe that this is the case, but
as a certain affinity between these widely separated islands
undoubtedly exists in some other groups, Mr. Ridgway’s view
may possibly turn out to be the correct one. Moreover, as
Mr. Ridgway points out, two of the Hawaiian Procellariidae,
viz., Aestrelata phaeopygia and Oceanodroma cryptoleucura
occur in the Galapagos islands.

Drs. Rothschild and Hartert * derive the whole avifauna
from America. All the same, their studies do not lead them to
adopt Darwin’s theory. They remain uncertain whether the
fauna points to a former land connection with the mainland
or whether it owes its existence to accidental dispersal. That
there should be this doubt in their minds is rather surprising,
considering their own statement that the geological evidence
is entirely opposed to the theory of a former land bridge be-
tween the islands and America.

The most recent study on the birds of the Galapagos archi-
pelago is that of Messrs. Snodgrass and Heller.t Taking
the general results of all these papers, there can be no
doubt that the avifauna is mostly related to South and Central
America and the West Indies, thus agreeing in that respect
with the mammalian fauna.

The reptiles of the Galapagos islands certainly offer the
greatest difficulty to the acceptance of Darwin’s theory that
the islands have risen from the floor of the ocean and have
never been connected with one another or with the continent.
Darwin observed only one small lizard belonging to a South
American genus, two different kinds of the great lizard
Amblyrhynchus—a genus confined to the islands—one kind
of snake and a land tortoise. He noticed that the one kind of
Amblyrhynchus lived altogether on land, the other being
semi-aquatic. The latter he described as a hideous looking
black creature up to four feet in length, with a laterally.
flattened tail and webbed feet. Sluggish in their movements
on shore these huge lizards are expert swimmers, darting

* Rothschild, W., and E. Hartert, ‘‘Ornithology of the Galapagos

Islands,”’ pp. 137—139.
+ Snodgrass, R. E., and E. Heller, “ Birds of the Galapagos Islands.”

a in

BIRDS OF GALAPAGOS ISLANDS 303

among the rock-pools and feeding there on seaweed. The
terrestrial species has no webs on the toes, and is of about the
same size as its aquatic relative, reddish brown above and
yellow underneath. It inhabits burrows, which occur in such
numbers that the soil is constantly giving way as one walks
over them, much to the annoyance of the tired traveller, as
Mr. Darwin * remarks. Some of the tortoises, according to
Darwin, grow to an immense size, yielding as much as two
hundred pounds of meat. Like the two lizards they are
entirely vegetable feeders.

When Dr. Ginther+ described the reptilian fauna of the
islands he distinguished five species of lizards instead of
the three mentioned by Darwin. The gigantic tortoises,
moreover, he thought, were referable to five distinct forms,
every one of them inhabiting a different island. He did not
speculate on their origin or past history, but mentioned that,
although large land-tortoises are now restricted to the two
widely separated regions of the Galapagos islands on the
one hand, and the Mascarenes and Seychelles on the other,
they formerly had an extensive range. In the Miocene Period
they lived in India, southern Europe and in North and South
America. We may consequently look upon the few survivors
as relicts of Tertiary times.{

More recent researches on the reptiles show that there are
far more distinct forms than was anticipated even by Dr.
Ginther. Mr. Garman § alludes to twenty-two species, among
them several geckos. He does not enter into a discussion as
to their origin; he merely states that two theories have been
advanced to explain the affinities of the fauna.

The Hopkins-Stanford Expedition of 1898 made such ex-
tensive collections on the islands that many additional forms
were discovered among the material sent to the Museum of the
Stanford University. Mr. Heller, who describes the reptiles,
mentions twenty-five species and several varieties. Nine of
these are giant tortoises, fifteen are lizards, and there is one
snake. Among the lizards there are six geckos (Geckonidae)

* Darwin, O., “ Journal of Researches,” pp. 278—284..

+t Giinther, A., “ Zoological Collections from Galapagos,”’ p. 66.
¢ Giimther, A., “ Gigantic Land-tortoises,” p. 253.

§ Garman, 8., “ Reptiles of Galapagos Islands.”

304 ORIGIN OF LIFE IN AMERICA

belonging to the two genera Gonatodes and Phyllodactylus.
The single species of Gonatodes is most closely allied to a
species found in the West Indies, while the genus also occurs
along the coast of Ecuador and Peru. Of the five species
of Phyllodactylus, four are peculiar to the Galapagos archi-
pelago and more or less nearly related to P. tuberculosus, the
non-peculiar species being distributed along the west coast
of Mexico, Central and South America as far as Ecuador.
All the species of Tropidurus, a genus belonging to the family
Iguanidae, are peculiar and closely related forms, most of
them being confined to different islands. The genus is prin-
cipally found in Peru and Ecuador. The two very large lizards
which Darwin observed really belong to distinct genera. Two
species of Conolophus are now recognised, while the aquatic
form still retains the original name of Amblyrhynchus cris-
tatus. Both genera of Iguanidae are quite peculiar to the
archipelago and distantly related to a South American genus. —
Finally, the snake Dromicus biserialis, which is met with on
seven of the islands, is nearly akin to D. chamissonis of Chile
and Peru.

The reptiles thus exhibit affinity with those inhabiting
western South America, Central America and the West Indies.
If they had reached the Galapagos islands by means of marine
currents, as has been alleged, one may be tempted to ask the
same question as I put before—Why should practically all the
species belong to ancient types ? Giant tortoises seem to have
become extinct on the continents in Miocene times, while the
lizards of the archipelago belong to the two families Gecko-
nidae and Iguanidae. Although no fossil representatives of the
Geckonidae are known, the resemblance of their vertebrae to
those of the Palaeozoic Microsauri has been commented upon
as indicating their ancient lineage. The genus Phyllodactylus
occurs in tropical America, in Africa, Madagascar, Australia
and on Norfolk and Lord Howe’s islands in the Pacific. A
single species inhabits the western Mediterranean region. The
distribution of the genus, therefore, is suggestive of a very
remote origin. Of the Iguanidae, as I have already pointed
out, (p. 127), we know that they lived in America in Creta-
ceous, and in Europe in Eocene times, while at present they
- are confined to North and South America with the outlying -

GALAPAGOS TORTOISES 305

Tres Marias, Galapagos and Chiloé islands. Beyond this
centre of distribution there are only two remote stations, one
in Madagascar, the other on the Fiji islands. We could not
have a better example of discontinuous distribution, which,
as Dr. Wallace has always urged, is a proof of antiquity.
Lastly, the Galapagos snake belongs to the ancient family
Colubridae, which also meludes Tropidonotus, a genus
specially alluded to (pp. 128 and 222).

In spite of these facts, Mr. Heller * expresses the opinion
that the archipelago is mostly of Tertiary age, and that the
fauna has been chiefly derived from material carried by ocean
currents. |

Still another expedition has lately been sent to the archi-
pelago by the California Academy of Sciences. Dr. Van
Denburghy who was asked to report on the reptiles feels quite
convinced that the islands must all at some former period
have formed parts of a single land-mass. In a letter which he
addressed to me, he implies that several species of snakes
inhabit the islands. He states that ‘‘the closest relatives
of the serpents of the Galapagos archipelago are native to the
Bahamas, Greater and Lesser Antilles, Costa Rica and the
whole of South America. This being true, the snakes of these
localities must have had a common origin. Hither the West
Indian and Galapagos snakes have been derived from South
America, or else all must be descendants of species occupy-
ing a great central land-mass which has sunk below the level
of the sea, leaving mere remnants in Central America,
northern South America, the Antilles and the Galapagos.
Hither view implies a former land connection and a con-
tinental origin of the Galapagos ophidian fauna. 1 cannot
bring myself to share the opinion of those who believe that
the fauna of the Galapagos has reached these islands by the
more or less accidental agency of the winds and ocean
currents.”

When Dr. Stearns { reported upon the land and fresh-water
snails inhabiting the Galapagos archipelago, he alluded to one
* Heller, E., “ Hopkins-Stanford Expedition : Reptiles,’ pp. 46—48.

+ Denburgh, John Van, “ Preliminary Descriptions of Land-tortoises,”’
i. 2s

{ Stearns, R. EH. C., ‘“ Mollusk-fauna of the Galapagos,” pp. 359—370.
L.A. x

306 ORIGIN OF LIFE. IN AMERICA

species of Hyalinia, a large number of Bulimuli, two Pupae,
one Leptinaria, a Succinea and a Helicina as haying been
collected on the islands by previous visitors. He then dilates
upon the various accidental means of transport, and concludes
that the agency of winds and ocean currents is amply sufficient
to explain the origin of the molluscan fauna. He acknow-
ledges that the archipelago is situated within an almost wind-
less area, where storms are of rare occurrence, yet maintains
that during the course of ages the climatic features may have
been different from those obtaining at present. He also
emphasises the fact of the tenacity of life of mollusks and
the length of time they are able to subsist without food, claim-
ing that a theory which will fairly explain a good portion of
the phenomena of distribution by such agencies and operating
directly under our eyes, is preferable to those, however plau-
sible and attractive, involving conjectural and remoter con-
ditions.

In his endeavour to support the theory of accidental dis-
tribution as applied to the origin of the Galapagos fauna, Dr.
Stearns seems to forget that no observation has ever been
made clearly indicating the conveyance of mollusks or their
eggs in drift-timber. Mollusks have never been found
in the crevices or under the bark either of trees encountered
on the sea or of those stranded on foreign coasts. Very
shortly after the trees are stranded, they are no doubt invaded
by all sorts of creatures seeking moisture and shelter; but the
theory of accidental distribution, so ably advocated by many
eminent naturalists still involves a good deal of the conjecture
which Dr. Stearns is so anxious to avoid. Although Dr.
Dall * fully acknowledges that we possess no actual proof
in support of the drift-theory, he also concurs with Dr.
Stearns in the opinion that there can be little doubt of the
land snails having been introduced to the Galapagos islands
in that manner. In his review of the molluscan fauna of the
islands, he mentions thirty-three species of Bulimuli, two
species of Vitrea and one of Conulus, two Pupae, four
Succineae, one Tornatellina (Leptinaria), one Helicina and
finally one Endodonta. Of these forty-five species, only a

* Dall, W. H., “Insular Land-shell Faunas.”

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GALAPAGOS MOLLUSKS 307

couple are probably common to the islands and the main-
land. All the others are restricted and quite peculiar to the
Galapagos archipelago.*

The genus Bulimulus, to which most of the Galapagos snails
belong, comprises mostly species with ovate large heavy shells,
which would seem to be peculiarly unfit for accidental trans-
port by marine currents, though many live almost habitually
on shrubs. As defined by Dr. Pilsbry, the genus is restricted,
as I have already indicated, to the western borders of South
and Central America and beyond the latter as far north as
Mexico and Lower California. Eastward it passes along the
northern States of South America to Brazil, it extends to the
Antilles, and from Mexico to the southern United States.
Thus it is limited to North, South and Central America, the
West Indies and Galapagos islands. The Melanesian genera
Liparus and Placostylus are closely related. The range of the
large family Bulimulidae is very similar, one group being con-
fined to America, the other to the opposite side of the Pacific,
from Tasmania in the south through Australia to China north-
ward, and eastward to the Society islands. One is almost
tempted to invoke a Pacific continent in explanation of this
curious discontinuous distribution. It seems as if the family
had originated in some central Pacific area and had taken
refuge on the nearest lands east and west on the disappear-
ance of its ancient habitat. But we need not consider this
problem at present.

There are three groups of apparently very closely related
Bulimuli in Chile and Peru, in the Galapagos islands and in
Lower California. The shell in these groups certainly is very
similar, being narrow and elongated, and possessing the same
texture. All the same, Dr. Pilsbry ¢ is of opinion that this
similarity in appearance is not to be looked upon as indicating
close relationship, but as a case of convergence produced by
similar environments. He recognises three sections of Buli-
mulus according to the sculpture of the apical whorls of the
shell. The first of these lives in Argentina, Chile, Peru and
Bolivia, the second in tropical America, the Galapagos islands

%* Dall, W. H., “Insular Land-shell Faunas: Additions.”
+ Pilsbry, H. A., “ Manual of Conchology,” (Pulmonata), X., p. 127,

x 2,

308 ORIGIN OF LIFE IN AMERICA

and West Indies, the third in Mexico and the United
States. ;

The two species of Vitrea (Hyalinia) seem to be related to
the Vitrea radiatula group, which, like Conulus, has a very
wide range in the Old World and the New. One of the Gala-
pagos species of Pupa is apparently found in Ecuador also,
the other is peculiar to the islands. The genus has a world-
wide range. All the species of Succinea, a genus which has
an enormous range, are confined to the islands. Tornatellina
chathamensis is closely rélated to the Hawaiian Achatellina
and belongs to a typically Polynesian genus. Helicina, as
already pointed out (pp. 157—158), has evidently invaded
America from the Pacific. Considering that it is an operculate
shell, and therefore supposed to be specially fitted for trans-
port across the sea by marine currents, it is surprising that
only a single species of Helicina should have taken advantage
of these facilities (compare Fig. 11). Lastly, one species of
Endodonta (E. helleri) has been observed on the archipelago. _
Of the Galapagos mollusks this is one of the most in-
teresting, because the extremely primitive genus EKndodonta
is almost confined to the Pacific region, including New Zea-
land, Tasmania, Australia, New Guinea and the Philippine
islands. Only St. Helena, where it is also found, lies entirely
outside the area. It is significant that not a single species is
known from the American or Asiatic mainlands or the West
Indies. )

I cannot help thinking that the attempt to derive the Gala-
pagos molluscan fauna from America is a mistake. The
family Bulimulidae is Pacific in origin, rather than American.
Succinea and Pupa have a wide range in the Pacific islands,
Tornatellina and Endodonta are altogether Pacific, being un-
known in America, Helicina is mainly Pacific, and it has
entered America from the west. Only Vitrea and Conulus may
be looked upon as typically American and Old World genera of
great antiquity. With their exception all the other genera
except two are more likely to have passed into America from
the direction of the Galapagos islands than vice versa. The
two others stopped short at the Galapagos archipelago and
went no further east.

Too little is as yet known of the insects of the islands and

AFFINITIES OF GALAPAGOS SNAILS 309

their distribution to be of much service in this study, but
Dr. Giinther records a woodlouse (Cubaris galapagoensis),
which is apparently related to a West Indian form. The genus
Cubaris, which is otherwise confined to the West Indies,
Florida, Central America, California and South America, is
the American representative of Armadillo. The latter has its
headquarters in southern Hurope. Cubaris, no doubt, owes its
presence in America to the fact that some ancestor common
to it and the European Armadillo crossed over by the trans-
Atlantic land bridge described in the last chapter.

On the whole, remarks Dr. Wallace,* the flora agrees with
the fauna as indicating a moderately remote origin, great
isolation, and changes of conditions affording facilities for
the introduction of organisms from various parts of the
American coast, and even from the West Indian islands and
the Gulf of Mexico. As in the case of the birds, he continues,
the several islands differ considerably in their native plants,
many species being limited to one or two islands only, while
others extend to several. |

A point of great importance in connection with the theory
of dispersal of seeds by marine currents is the condition of
the coasts of the Galapagos islands. The dried up desert
aspect of the islands on landing has been commented upon by
Darwin. Dr. Wolf} gives us his impression of the same
islands during the rainy season. The lower zone up to six
hundred feet is only very sparsely covered by vegetation. The
whole landscape has a greyish-brown appearance. A Lantana,
a couple of Crotons and a few Euphorbiaceae and Compositae
are the principal members of this wretched flora. The only
plants that thrive in this district are two giant Cactuses,
reaching to a height of about twenty feet. They seem to
select the driest and roughest spots, where nothing else will
grow. Herbaceous plants are restricted in this lower zone
to a few parched grasses and a few shrivelled diminutive
plants. There are very large districts, moreover, where
nothing whatsoever will grow, the ground being paved, as it
were, with enormous blocks of lava. At a height of about

* Wallace, A. R., “Island Life,” p. 289.
t Wolf, Th., “ Die Galapagos Inseln,” pp. 257—260.

|

310 ORIGIN OF LIFE IN AMERICA

seven hundred feet the scenery changes completely. A fresh
and moisture-laden wind greets us from the south-east, the
ground is covered with short dense grasses, evergreen, shady
little woods are dotted about here and there, and the flora
as a whole is quite different from that below. Those ac-
quainted with the flora of Ecuador will feel as if transplanted
to the woods of the Paramo region, which flourish at a height
of about 9,000 feet. The most striking character of the
flora is its strong endemism, every one of the larger islands
having its peculiar species, which do not range to the
others even when the islands are in close proximity to one
another.

From Dr. Wolf’s graphic description we can gather valu-
able information. In its strongly endemic character the flora
of the archipelago agrees perfectly with the fauna. As among
the animals so it has been noticed among the plants that the
various islands all possess their own species, though the latter
are related to one another. But, in answer to our inquiries
into the causes of this singular distribution, we are told by
Dr. Wolf that he concurs with Darwin in the belief that the
islands received their plants, as well as their animals, by acci-
dental means of transport. He does not specify these means
of transport. Darwin* makes it perfectly clear to us that
winds could not have played any part in it. ‘‘ As the archi-
pelago is free to a remarkable degree,’’ he says, ‘‘ from gales
of wind, neither the birds, insects, nor lighter seeds, would
be blown from island to island.” If the seeds were carried
by marine currents from the mainland to the archipelago,
how were they afterwards conveyed from the inhospitable
shores of the islands across the almost absolute desert of
the lowlands to the higher level ? We are unacquainted with
any forces except wind, which would carry the seeds to a
height of seven hundred feet, but Darwin expressly tells us
the islands are remarkably free from wind. Moreover, we
should expect the plants found at that height in the Galapagos
islands to agree to some extent with the flora of the lowlands
of the continent. Few, if any, seeds carried down by rivers
would come from the highlands of the Andes. Yet the Gala-

* Darwin, C., “Journal of Researches,” p. 290.

FLORA OF GALAPAGOS ISLANDS 311

pagos flora possesses affinities with the highlands rather than
the lowlands.

In this brief account of the main features of the fauna and
flora of the Galapagos archipelago I have endeavoured to state
mainly the opinions of those who agree with the theory of
elevation as propounded by Darwin. Some authorities formu-
lated no decisive views on the subject. Itis currently believed
that the first criticism of this theory was brought forward by
Professor Baur * in 1890, in a paper on the variation of the
genus Tropidurus in the Galapagos islands. Although it was
the first serious criticism, Mr. Andrew Murray + remarked
much earlier that Darwin’s observations on the Galapagos
fauna. had led him to an entirely different conclusion. “ The
American type of the whole group,” he says, ‘ speaks pri-
marily of connection with the continent. The family facies
of the group inter se, speaks of a period when the whole
islands were separated from America, but united to each other.
The endemic peculiarity of the species of each individual
island tells of subsequent separation and change wrought
in each, probably at the same time, by the alteration of climate
from continental or terrestrial, to isolated and oceanic.”

It was not until 1891, when a more popular account of
Professor Baur’s views appeared in the “ American Natu-
ralist,’’ that his opinions led to considerable discussion both
in America and in Kurope. It had seemed as if Darwin’s
theory, supported as it was by Wallace, Hooker, Agassiz and
many other naturalists of less note, was unassailable. Never-
theless, Professor Baur’s careful reasoning induced many sub-
sequent writers to adopt his views in preference to older
ones. He urged with Dr. Wallace that all islands may be
divided into Continental and Oceanie ones. The first have
developed from continents or larger bodies of land through
isolation or subsidence. The second have not been so formed,
but have arisen from submarine portions of the earth by eleva-
tion. He thought that the fauna and flora of the first group of
islands would be more or less harmonic, that is to say, the
islands would be like satellites of the continent from which
they took their origin. The fauna and flora of the second

* Baur, G., “ Variieren der Eidechsen-Gattung Tropidurus.”
+ Murray, A., “ Distribution of Mammals,” p. 17.

319 ORIGIN OF LIFE IN AMERICA

group, however, ought to be disharmonic, for it will be com-
posed of quite a different mixture of animals and plants, since
they have been introduced accidentally from other land areas.
Accidental immigrants will also reach the continental islands
eventually in a similar manner. ‘Thus continental islands
may be composed of two faunal and floral elements, an original
and a secondary one. Oceanic islands, on the other hand, can
only contain a secondary faunal and floral element, and will,
therefore, not exhibit harmonic distribution. Since the dis-
tribution of the animals and plants on the Galapagos islands
is harmonic, just as it is on the West Indian islands, both of
them, according to Professor Baur, represent the remains
of land-masses that have been split off from the adjoining
continent, and they have not risen from the floor of the
ocean. Though agreeing in his final conclusions with Pro-
fessor Baur, I am unable to follow him in regard to his defini-
tions of “harmonic” and “disharmonic.” Some of the
Pacific islands are looked upon by Professor Baur himself as
remnants of a Pacific continent, others, I believe, are not.
Where is the exact distinction between them in the nature of
their fauna ?

A few years later Professor Baur * once more returned to
the subject in order to answer the objections brought against
his theory by numerous critics. He also intended to make some
remarks on the geological history of the Pacific Ocean, and
from his preliminary observations it is evident he believed
in its comparatively recent age; but before he could complete
his interesting series of articles his sudden death unfortu-
nately deprived us of further communications. From his
writings, however, we know that Professor Baur believed that
the Galapagos archipelago represented the remnants of a large
peninsula which joined the West Indies by way of Cocos
island and Central America. As some of his critics maintain
that in his views Professor Baur stands almost alone, and is
opposed by most of those who have discussed the fascinating
problem of the origin of the Galapagos archipelago, a few
remarks may be permissible in support of this theory.

Alluding to the gigantic land-tortoises which have survived

* Baur, G., “New Observations on the Galapagos Islands.”

BAUR’S GRITICISMS 313

on the Galapagos and various other islands, Dr. Gadow * asks
the pertinent question—Where did all these creatures come
from, and how did they get to these oceanic islands ? Acci-
dental transport is out of the question, as land-tortoises are
drowned within a few hours after immersion in water. Since
none of their kind inhabit the great continents now, although
they lived there formerly, we are constrained to assume that
the existing species are the survivors of tortoises which pro-
ceeded to the islands when they were connected by land with
the adjoining continents. In another place Dr. Gadow quotes
the Galapagos tortoises as supporting the hypothesis of an
Oligocene extension of land, considerably to the west and
south of the present Central America.‘ In his maps illus-
trating the palaeogeography of Middle America, he actually
joins the Galapagos islands with the Antilles, as Professor
Baur had done, by way of Cocos island.+

Professor Boettger { approves of the results obtained by
Professor Baur’s methods of investigation, arguing that the
facts of distribution are much more easily explained by the
assumption of a former land connection between the Gala-
pagos archipelago and Central America than by the theories

_ hitherto accepted.

While in general agreement with the same views, Dr.
Sarasin § suggests that the ancient land bridge lay in a north-
eastward direction, that is to say, from the Galapagos islands
towards Mexico rather than to Ecuador.

The fossil marine mollusks and their distribution are em-
ployed by Dr. von Ihering || in support of the same theory.
He draws attention to the remarkable fact that the species
of the Tertiary Chilean deposits only appear on the Cali-
fornian coast in Pleistocene times, and that similarly the
Californian Tertiary forms only reached the coasts of Chile
about the same time. On these grounds alone Dr. von Ihering
bases his theory of a Tertiary peninsula extending westward
into the Pacific Ocean and embracing the Galapagos islands,

* Gadow, H., “ Amphibia and Reptiles,” p. 373.

+ Gadow, H., “‘ Mexican Amphibians and Reptiles,” p. 211.

{ Boettger, O., “ Baur’s Differentiation of Species,” p. 462.

§ Sarasin, F’., “ Die Fauna der Galapagos Inseln,” p. 293,

|| Ihering, H. von, “ Fauna der Neotropischen Region,” p. 296.

314 ORIGIN OF LIFE IN AMERICA

-which thus acted as a barrier in separating the North
American from the South American fauna (see Fig. 17).

That the distribution of reptiles and mollusks on the Gala-
pagos islands points to a former land connection with the
American mainland is especially urged by Dr. Arldt,* but,
like Dr. Ortmann, he thinks the islands must have been iso-
lated since the end of the Mesozoic era. The land connection
referred to is shown in Dr. Ortmann’s + map illustrating the
distribution of land and water during the Upper Cretaceous
Period (Fig. 15).

As regards the flora, Messrs. Robinson and Greenman con-
tend that no species to be found on the different islands illus-
trates the noteworthy racial divergence in related forms better
than Euphorbia viminea. ‘This species differs markedly in
foliage from any other known member of the large genus
Euphorbia and is characteristic of the Galapagos archipelago.
Being essentially a desert plant, it can subsist even upon those
islands of the archipelago which are of low altitude and do
not attain the upper regions of moist atmosphere. The most
cursory inspection of the, forms from the different islands
discloses marked variation in the contour, size, thickness,
rigidity and colour of the leaves, as well as in the length of
the internodes, colour of the stems and so forth, whereas more
careful examination shows that these are not mere individual
differences, due to chance, state of development, or individual
environment, but that each form appears in general to be
restricted to a single island.

The question consequently presents itself, according to .
Messrs. Robinson and Greenman,{ “If this archipelago is
composed of islands of elevation, built up from the sea-floor
independently by volcanic action, how has such a distribution
been effected ?’’ If the vegetation has been derived from the
mainland by chance transportation of seeds, it is quite impos-
sible to believe that each island has received a slightly different
form of the same species, and we are forced to the much more
natural assumption that racial and varietal divergence has

* Arldt, T., “ Entwicklung der Kontinente,” p. 116. _

+ Ortmann, A. E., “ Distribution of Decapods,” p. 381.

¢{ Robinson, B. L., and J. M. Greenman, “ Galapagos Flora,” pp. 135—
137.

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EUPHORBIA AND ITS ORIGIN 315

come about after the introduction of the species on the islands.
Continuing the supposition that these are islands of elevation,
the seeds of Euphorbia viminea must have reached them in
one or two ways. Hither every one of the nine islands where
we know the species now to occur must have received its seed
directly from the mainland, or, what is much more natural,
seed must have reached one or more of the islands and from
these have spread to the rest. That the same species should
have reached all these islands presupposes a considerable
facility of transportation. But as soon as this is granted,
it is impossible to understand the highly individual develop-
ment of the forms on the different islands. For relative or
complete isolation seems necessary to account for the racially
- divergent floras of the islands, and especially for the occur-
rence of only one form on each island. On Dr. Baur’s
assumption of a former union between the islands, and sub-
sequent separation by subsidence, the authors maintain that
not only is an explanation of the facts possible, but the exist-
ing flora of the archipelago is just that which would most
naturally result from such an origin. A former union of the
islands would account at once for the occurrence of identical
ancestral species upon the different members of the-group. |
The subsequent separation would give the needed isolation for
varietal and racial divergence, while the latter could not have
come about if a continual interchange of seed were taking
place from island to island.

Messrs. Robinson and Greenman’s careful reasoning is
just as well applicable to the birds of the genera Geospiza,
Certhidea and Nesomimus, to the reptilian genera Tropidurus
and Testudo,.and to the snail Bulimulus as it is to Euphorbia
viminea, and from a study of any of them we should come to
precisely the same conclusion as these authors. Mr.
Hemsley * thinks the biological data which we possess from -
the Galapagos islands are strongly in favour of Professor
Baur’s views, and he supposes the area on which the islands
stand to have been continued eastward to the mainland of
Veraguas.

Professor Stewart does not produce any new data for or

* Hemsley, W. Botting, “ Insular Floras,’”’ VI. (A), p. 299.

316 ORIGIN OF LIFE IN AMERICA

against the theory of a former land connection between the
islands and the mainland. He scarcely discusses the problem
from a botanical point of view, but assumes that the Gala-
pagos islands are of oceanic origin.*

Personally, I am in agreement with Mr. Andrew Murray’s
and Professor Baur’s theory that the archipelago originated
through subsidence of a land-mass which was connected with
the mainland. From the latter the islands received the prin-
cipal members of the fauna and flora, and these progressed
from the one to the other on a solid land surface. Subse-
quently, possibly owing to volcanic disturbance, the land sub-
sided, leaving only the mountain tops with their animals and
plants as fragmentary relicts of a rich and varied fauna and
flora. So far [am in agreement with Professor Baur’s theory,
but I believe that the geological history of the Galapagos
archipelago forms only part of a much larger and far more
complex problem. In the first place, it is evident that the
whole fauna and flora of the Galapagos islands cannot have
originated in Central America or the West Indies. A large
proportion of the animals and plants seem to have their
nearest relations in Ecuador and Colombia. Others point
to a still more southern or northern origin. If we derive the
fauna and flora principally from a former land connection
with the mainland of America, that connection must have had
several branches. ‘The affinities of the archipelago appear
to be chiefly with Central America and Ecuador and much
less with Chile. On the other hand, a certain relationship, for
instance among the Bulimuli, exists with the southern ex-

tremity of Lower California. All these different areas of.

North, Central and South America may have been joined
with the Galapagos land-mass by peninsulae, though one or
more of them may have become disconnected long before the
others. Dr. Arldt + indicates something of that kind in his
map illustrating the conditions of land and water in Creta-
ceous times. At least, he connects western Mexico and
Ecuador by a broad land bridge westward of Central America
and across the area of the Galapagos archipelago. I ventured

* Stewart, A., “ Botanical Survey of Galapagos Islands,” p. 239.
+ Arldt, J., “ Entwicklung der Kontinente,’’-—Karte 19.

ee

ORIGIN OF GALAPAGOS FAUNA 317

to propound the theory that North and South America might
have been joined by means of a land bridge between Mexico
and Chile across the Galapagos islands at a time when the
greater part of South America was still submerged.* But
that land connection is evidently one which must have ceased
to exist in its entirety, at least in early Tertiary times (see
Fig. 16). .

I have likewise alluded above to a supposed affinity of some
of the Galapagos birds to species found in the Sandwich
islands, pointing out that in other groups this relationship
undoubtedly exists, although only to a slight extent. I have
mentioned examples among the mollusks. Among plants the
composite Lipochaeta is a good example. The genus is con-
fined to the Sandwich islands, except one species which in-
habits the Galapagos archipelago. Instances of affinity of
the Sandwich islands with Mexico and Central America also
occur, though as a rule the relationship is a remote one.
Still, it has been tentatively suggested by several writers that
some time or other in the past Mexico or California were
joined by a land bridge to these islands. It might be con-
sidered somewhat beyond the scope of this work to discuss a
faunistic relationship of this nature, but it really forms part
of the great problem as to the origin of the older Asiatic stock
on the American continent.

What I described above (p. 97) as the latest or most recent
immigration of Asiatic types into North America took place, I
think, in Pliocene and perhaps early Pleistocene times.
A large proportion of the more northerly animals and plants
now living in- North America readily reveal their Asiatic origin
as slightly modified descendants of a stock once common to
both Asia and North America. These we must regard as
the offspring of the latest Asiatic invasion. The American
species which thus indicate their Asiatic lineage were des-
cribed as Asiatic invaders principally in the early chapters.
In the fourth chapter the time and the place of their invasion
across Bering Strait were more fully discussed. Throughout
the subsequent chapters I drew attention to the existence
of severally geologically more ancient invasions from Asia, ex-

* Scharff, R. F., “ Early Tertiary Land-connection,” pr 525.

318 ORIGIN OF LIFE IN AMERICA

pressing my belief, contrary to the opinion of almost all those
who had occupied themselves with this problem, that these
earlier Asiatic immigrants took an entirely different route
from the later ones. The opinion I had formed was founded
on a variety of circumstances.

If the theory I had formulated is correct, namely that the
effects presented by the Glacial Epoch were due to the
simultaneous closing of the Arctic Ocean from the Atlantic
and Pacific by the formation of two land bridges, one
of which connected North America with Europe in the
east, while the other joined North America and Asia in
the west (see Fig. 7), the warmer climate in pre-Glacial
times must have been due to the fact that the Arctic
Ocean then received a greater amount of heated water
than it does now. That the two land bridges must have existed
at nearly the same time seems to be amply demonstrated from
biological evidence. During the Miocene Period the climate
in the extreme north of Hurope and North America must have
been much milder than in Pliocene times. The evidence from
northern Hurope is against the supposition that the Gulf
Stream entered the Arctic Ocean more freely during the
Miocene Period than it does at present. The Japanese
‘““Kuroshiwo,’’ or possibly some even more powerful marine
current, must have passed, therefore, entirely into the basin
of the Arctic Ocean across Bering Strait. I remarked before
(p. 96) that the appearance of certain Pacific species of
mollusks in the English Crag deposits may perhaps be due
to this cause. It was not until Pliocene times, according to
Professor J. P. Smith,* that the marine faunas of Japan
and the western coast of North America began to be re-
markably similar, thus implying that a migration at that time
took place along a continuous shore-line. The Californian
Miocene marine deposits seem mostly to contain endemic
species with a slight admixture of southern and circumboreal
ones. All this evidence favours the view of an open Bering
Strait in Miocene times, and a closed one during the Pliocene
Period. Dr. Dall + states that the Kenai leaf beds in Alaska
(now generally considered of Hocene or Oligocene age) are

* Smith, J. P., ‘“ Periodic Migrations,” pp. 225—226.
+ Dall, W. H., “Correlation Papers—Neocene,”’ p. 261.

HISTORY OF PACIFIC OCEAN 319

succeeded by Miocene beds with a marine fauna. Similarly -
he describes a series of Miocene marine mollusks from sand-
stones obtained at the head of the Gulf of Penjinsk on the
opposite shore of Asia. As in Alaska, these Miocene sand-
stones are apparently resting on leaf-bearing lignites, thus
strengthening the assumption of a wide and freely open
passage in the north, between the Pacific and Arctic Oceans.*
Professor Schuchert} separates North America from Asia by
a marine channel throughout Miocene and Pliocene times in
his maps illustrating North American paleogeography. All
the evidence, says Mr. Knopf,{ from which conclusions of
some positiveness can be drawn, record only epochs during ©
the Tertiary Era of more widely spread submergence and
increased separation of the continents. And yet his exten-
sive studies of the mammalian fauna led Professor Osborn §
to the conclusion that the emergence of continents progressed
during the Miocene Period and that North America was
broadly united with eastern Asia. How can we reconcile these
diametrically opposite views ? I have shown that in Oligo-
cene times, or during part of that Period, a trans-Atlantic land
connection probably enabled the Old World types to travel to
North America. A Bering Strait land bridge is not essential,
therefore, in explaining existing Oligocene or Eocene affini-
ties between the Old World and the New. But I have given a
large number of instances among North American plants as
well as animals, indicating a direct migration either from Asia
to North America or vice versa, in early and late Tertiary, at
any rate in pre-Pliocene times. I need only allude again to
the close relationship of the hellbender of the eastern States
to the Japanese giant salamander, of the blue-tailed skink
of the eastern States and Japan, and of the absolute identity
of the American and Japanese ground lizards (Lygosoma
laterale). The only living relation of the American alligator
inhabits the Yangtse river in China; the nearest akin to the
American green snakes (Liopeltis and Cyclophis) reside in
‘south-eastern Asia. The family of snapping turtles (Chely-

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320 ORIGIN OF LIFE IN AMERICA

dridae) are confined to America and New Guinea, the Aglypha,
a division of the Colubrine snakes, inhabit south-eastern Asia
and Papuasia, except one genus which is restricted to Central
America. The pythons are mainly Australian and southern
Asiatic, but a single species (Loxocemus bicolor) lives in
southern Mexico. The American land-snail Bulimulus, as
we have seen, has its nearest relation (Placostylus) in
Australia and the islands of the western Pacific. The geogra-
phical distribution of the land isopods belonging to the group
of Spherilloninae, from New Zealand, Australia, Polynesia,
south-eastern Asia and Japan to south-western North
America, seemed to Mr. Budde-Lund * so very peculiar that
he invoked a Pacific continent to explain it. As a matter of fact
we have very numerous similar instances indicating a striking
faunistic affinity between North America and eastern Asia.
But these examples belong to an entirely different category
from the animals and plants referred to as forming the later
Asiatic immigration. Certain closely allied or even identical
forms such as the alligator, the blue-tailed skink and the
ground-lizard in America and eastern Asia apparently point
to a geologically recent faunistic interchange between these
countries. But alligators are known even from the earliest
Tertiary deposits, while the range of the ground-lizard
(Lygosoma) from New Zealand, Australia and southern Asia
as far north as Japan, indicates that the genus is probably of
Mesozoic origin, and that we have to deal with a remarkably
persistent ancient type.

When we take a general survey of the range in North
America of these older Asiatic animals (and the plants per-
fectly agree with them), we find that their number decreases
as we go north-westward, but increases towards the south-
west and Central America. The whole stream of these ancient
Asiatic immigrants seems to have issued forth from the south-
west, precisely from the same part of North America that
also yielded the Huropean colonists. It is in south-western
North America, I think, that we have to search for indications
of the older land connection with Asia, and not in the Bering
Strait. Another point that strikes us during our general

* Budde-Lund, G., “ Revision of Crustacea Isopoda Terr.,’’ II., p. 40

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THEORY OF A PACIFIC CONTINENT 321

survey is that the American and Asiatic forms related to one
another are in Asia mainly confined to the south-eastern
border generally, or to Japan. Australia, New Zealand and
New Guinea also possess a large number of species and genera
very closely allied to west American ones. These seem rarely
to extend further north in Asia than Japan. Are we to throw
a bridge across the Pacific ocean from Japan in order to find a
possible explanation of this former invasion of south Asiatic
and Australian types into western America, or does any other
theory meet all the facts of the case ?

Since Dr. Augustus Gould * first mooted the hypothesis of
a former Pacific continent about sixty years ago, the idea has
been widely discussed by biologists and geologists. Mr.

-Murray’s + attention seems to have been first drawn to the

subject by the occurrence of the beetle Meristhus serobinula
in Mexico and China, and by the presence of the mole Urotri-
chus in California and Japan. The Japanese and Californian
moles are no longer placed into the same genus, but no one
doubts that the American Neiirotrichus and Japanese Urotri-
chus are very nearly related to one another and that they
must have had a common ancestor.

The supporters of the theory of the permanence of our great
ocean basins explain such cases by means of a former Bering
Strait land bridge, but, as already stated, the solution of this
problem must be sought elsewhere. That several of the pre-
mises on which the theory of the permanence of ocean basins
is founded are incorrect has been demonstrated (pp. 274—
277). Darwin’s theoretical considerations on the formation
of coral reefs and atolls, which demanded a long continued
subsidence of the mid-Pacific region, have been amply veri-
fied. To put his subsidence theory to a practical test Darwin
suggested that a boring should be made into one of the cores
of an atoll. Through the perseverance and energy of Pro-
fessor Sollas { and Professor Edgworth David a boring on
Funafuti atoll was carried to a depth of one thousand one
hundred and fourteen feet, where cores were obtained showing
that the whole mass of rock was composed of pure coral. Since
* Gould, A., “Remarks on Mollusks,” p. 78.

+ Murray, A., “ Geographical Relations of Coleopterous Faunas,”’ p. 37.
t Sollas, W. J., “The Atoll of Funafuti.”
L.A. Y

322 ORIGIN OF LIFE IN AMERICA

the organisms that form coral reefs are unable to live at a
greater depth than one hundred and fifty feet, it is manifest
that the floor of the ocean must have subsided very slowly
and continuously, thus enabling the reef-building corals to
raise their structures to the requisite depth of water. The
verdict of Funafuti is thus clearly and unmistakably in favour
of Darwin’s theory of subsidence. The fact that a slight local
elevation seems to be taking place in some parts in no way
detracts from the truth which has been so firmly established.

It would lead me too far from my main object to allude to
the numerous papers that have been written on the Pacific
Continent controversy. After Gould and Murray it was
Captain Hutton,* I think, who again revived the theory, which
he later on discussed in his presidential address to the Philo-
sophical Institute of Canterbury in New Zealand. His idea
was that New Zealand, eastern Australia and India formed one
biological region in early Mesozoic times. In Lower Cre-
taceous times a large Pacific Continent extended from New
Guinea to Chile, and from the latter a long lobe of land
stretched southward to New Zealand. This Pacific Continent,
in his opinion, supported plants, insects, snails, frogs, some
lizards, perhaps snakes and a few birds, but no mammals.
Later on, during the Cretaceous Period, New Zealand became
separated, while the Pacific Continent broke up.

More recently Dr. von [heringy alluded to a Pacific Con-
tinent which he believes to have gradually subsided during
the Mesozoic Era, but without going into further details as
to its nature and size. I may mention that the supposed
antarctic land connection between Patagonia and New Zea-
land is a subject which I am not dealing with at present.
Dr. Pilsbry assailed the problem entirely from the point of
view of the molluscan distribution. He points out that many
genera of land-snails reach back to the Oligocene Period
unchanged save in specific characters, and that the modern
family groups of these snails undoubtedly diverge far back
in Mesozoic time. Now it is a most significant fact that the
Pacific islands are almost entirely tenanted by the most primi-

* Hutton, F. W., “ Origin of Fauna and Flora of New Zealand.”

+ Ihering, H. von, “Relations between New Zealand and South
“America,” p, 444.

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THEORY OF A PACIFIC CONTINENT 323

tive and oldest groups of land-snails. And, as Dr. Pilsbry,
facetiously puts it, “it is very easy to show that snails may
have been carried from place to place by a hurricane, a float-
ing tree or ‘ floating island,’ or that their eggs may find room
in the pellet of earth clinging to a bird’s feather, but it is in-
cumbent upon the theorist who peoples the mid-Pacific islands
by such means to show why such dominant groups as the Heli-
cidae, Bulimulidae, Rhytididae, Streptaxidae—in fact the
whole Holopoda and Agnathomorpha, with the higher mem-
bers of the aulacopod families, as well as the higher opercu-
lates—should have utterly failed to take advantage of these
means of transport.’’ Instead of being a faunal dependency of
the Australian or Oriental regions, Polynesia has every ap-
pearance, says Dr. Pilsbry, of being a region which started
with a fauna long antedating the present Australian and
Oriental faunas, developing along its own lines, retaining old
types because they did not come into competition with the
higher groups of animal life. Dr. ’Pilsbry’s conclusion is that
a Pacific Continent existed, which was finally separated from
other lands as early as the middle of the Mesozoic Era, and
that the northern portion became disconnected when the
remainder was still joined to the mainland.*

A careful review of the distribution of the ants and lizards
in particular led Professor Baur + to formulate the theory
of a former Indo-Pacific Continent extending from Malaysia
to the west coast of America. He looked upon the Pacific
islands as the last remnants of this continent, which still
existed, he thinks, until the commencement of the Miocene
Period.

Mr. Hedley,t who took part in the famous Funafuti Ex-
pedition, and has had the advantage of studying the problems
of dispersal on the spot, altogether disbelieves in a Pacific
Continent in the sense of Baur, Pilsbry and Hutton, but he
suggests that New Zealand was formerly connected with Aus-
tralia by way of New Caledonia, the New Hebrides, Solomon
islands and New Guinea. Even the Fiji islands come within
this scheme. Some years earlier he had already demonstrated

* Pilsbry, H. A., “Genesis of Mid-Pacific Faunas,” pp. 569—578.

} Baur, G., ‘‘ New Observations on the Galapagos Islands,” p. 869.
t Hedley, C., ‘‘Zoogeographic Scheme,”’ pp. 400—405.

y2

324 ORIGIN OF LIFE IN AMERICA

the essential unity of the area inhabited by the snail Placo-
stylus,* thus regarding New Zealand and the archipelagoes of
Solomon, Fiji, New Hebrides, Loyalty, New Caledonia and
Lord Howe as portions of a shattered continent which he
called the “ Melanesian plateau.” The short review on the
subject by Dr. Holdhaus} in favour of a Pacific Continent in
Tertiary times adds little to the arguments already advanced
by Professor Baur. |
A most determined and thoroughgoing onslaught on the
theory of a supposed former Pacific Continent was recently
made by Mr. Guppy. It seems scarcely fair to compare the
results of his studies with those just alluded to, because
he derives his arguments almost altogether from the flora
of the Pacific islands, while the others were founded on
faunistic data. Still, Mr. Guppy’s works { contain a great
deal of personal observation, and his careful labours in
this particular field of enquiry will be sure to attract
the serious attention of the student of geographical dis-
tribution. His discussion of the subject is disappointing
in some respects. “If the distribution of a particular
group of plants or animals does not accord with the pre-
sent arrangement of the land,” he remarks, “it is by far
the safest plan, even after exhausting all likely modes of
explanation, not to invoke the intervention of geographical
changes.” A little further he explains “I scarcely think
that our knowledge of any one group of organisms is ever
sufficiently precise to justify a recourse to hypothetical altera-
tions in the present relations of land and sea.” In reading
such passages one wonders whether Mr. Guppy can have
become acquainted with the science of geology, or with the
principles that underlie the geographical distribution, for
example, of mammals. His opinions differ radically even from

those of Dr. Wallace, who cannot be said to have been unduly ~ J |

rash in any of his conclusions as to former changes of land

and water. One would also expect from Mr. Guppy an abun-

dance of important facts concerning the dispersal of seeds

by the various means of accidental transport. But he tells us
* Hedley, O., “ Range of Placostylus,” p. 339.

+ Holdhaus, K., “ Argumente f. d. Existens eines pazif. Kontinents.”’
¢ Guppy, H. B., “A Naturalist in the Pacific,” I., p. 380.

tienda: tea ae

GUPPY ON PACIFIC CONTINENT 325

that the story of plant distribution in the Pacific is bound
up with the successive stages of decreasing activity in the
dispersing agencies. He thinks that the area of active dis-
persion, as illustrated by the non-endemic genera of plants,
at first comprised the whole of the tropical Pacific.* After-
wards it was limited to the southern Pacific, and finally to the
western Pacific only. The birds that carried seeds all over this
ocean became more and more restricted in their range, pro-
bably, as Mr. Guppy suggests, on account of increasing
diversity of climatic conditions. The plants of necessity re-
sponded to the ever narrowing conditions of bird-life in this
ocean, the differentiation of the plant and bird taking place
together.

Mr. Guppy dislikes the idea of hypothetical alterations in
the present relations of land and water, and yet what an
amount of hypothesis he has to resort to in his endeavour to
explain the theory which he is so anxious to support! There
is not a scrap of evidence for the belief that dispersing
agencies have practically ceased at the present time, nor that
the migrations of birds have diminished. On the contrary,
ornithologists have done their utmost to trace the origin of
all bird migrations to the gradually increasing diversity of
climatic conditions during the Tertiary Era, which they sup-
pose to have culminated in the Glacial Epoch. Although we
have little evidence for such a belief, it seems a reasonable
supposition. But what can be said in favour of Mr. Guppy’s
theory, that, owing to the increasing diversity of climatic con-
ditions, the seed-carrying birds have become more restricted,
that is to say, less migratory ?

A careful perusal of Mr. Guppy’s work must make it evident
to anyone, that, although plants have far greater facilities for
accidental transport, and have in many cases actually been
thus conveyed from one land surface to another, they agree
on the whole perfectly with animals, in so far as the Pacific
islands are largely tenanted by very ancient types. If we adopt
the theory of accidental dispersal for the origin of the Pacific
island flora, we must apparently assume that the means of
occasional conveyance were far more efficient in former times

* Guppy, H. B., “A Naturalist in the Pacific,” II., pp. 519—520.

326 ORIGIN OF LIFE IN AMERICA

than they are at present. Even Mr. Guppy, however, some-
times relents and partly withdraws from his precepts when
confronted by really difficult cases of distribution. Thus he
acknowledges that the conifer Dammara vitiensis, which grows
on the Fiji islands, is unfitted for accidental dispersal by any
of the known modes of conveyance. The genus Dammara is
confined to New Zealand, eastern Australia, New Caledonia,
the New Hebrides and Fiji islands. From this region it ex-
tends westward to Java and Borneo, the centre of distribution
being in the western Pacific. The absence of the genus from the
neighbouring Samoan and Tongan groups is, as Mr. Guppy *
remarks, very significant, and it is evident that the ordinary
agencies of dispersal by birds, winds or currents have here
failed to extend Dammara over a few hundred miles of sea.
For once Mr. Guppy concedes, therefore, that the present
relations of land and sea do change sometimes, and that,
“nolens volens,” we must admit that Dammara may well be
cited in support of any continental hypothesis affecting the
western Pacific. Later on, in fact, he expresses the opinion
that the Fiji islands mark the site of a Mesozoic continental
area in this region.

There is thus a certain amount of distributional evidence
in favour of the theory of the existence of a large land sur-
face in the western Pacific. Whether the remainder of that
ocean was ever completely occupied by land is a more difficult
question to answer. But even on the distant Marquesas
islands granites and gneisses occur,.as I mentioned before.
In the tuffs of the Kermadec islands numerous boulders of
hornblende granite have been found. New Caledonia consists
of an ancient series of mica schists and slates with a general
north-easterly strike. There are also shales containing fossils
identical with those of the New Zealand Trias, followed by beds
of coal of Jurassic age. Gneisses, crystalline limestones and
serpentines, like those of New Caledonia, are reported from the
New Hebrides. Crystalline schists, granular limestone,
granite, diorite and gabbro have been discovered on the Fiji
islands. The occurrence on the Tonga group of fragments
of garnet, tourmaline and uralitic gabbro suggests the close

_ * Guppy, H. B., “A Naturalist in the Pacific,” II., pp. 297—306,

DARWIN’S THEORY OF CORAL REEFS = 827

proximity of an area of metamorphic rocks, while a series of
plutonic rocks have recently been described from Tahiti.

Thus, according to Mr. Speight,* there appears to be geo-
logical evidence of the former extension of continental con-
ditions over a large area of the mid-Pacific region. As he
remarks, it is highly probable that many volcanic islands
classified as oceanic will ultimately have to be looked upon
as built up on the remnants of a continental area. We may
imagine that a large land area or continent covered the greater
part of the present Pacific Ocean in Palaeozoic and early
Mesozoic times, and that there was a subsidence during later
Mesozoic and Tertiary times with more recent local elevations.

Professor Haug, discusses the Pacific problem from
another point of view. His studies of the geosynclinals, which
he calls the essentially mobile regions of the earth’s crust,
led him to the conclusion that the circumpacific geosynclinal
implied the former existence of a continent in place of the
present Pacific Ocean.

The well-known parallelism of the different groups of Pacific¢
islands has likewise been utilised in support of the same
theory. It may be explained by the supposition that these
islands are either the remnants or the initial stages of a
series of mountain chains.{ The Funafuti boring results seem
to point to the first of these as the more likely assumption.

That Darwin’s theory of subsidence still meets with a good
deal of determined opposition by the believers of the per-
manence of ocean basins may be gauged from Sir John
Murray’s writings on the structure and origin of coral reefs.
I think it is unnecessary for me to discuss the bearings of his
arguments on the American problems raised in this chapter,
because, in the first place, it seems probable that both Mur-
ray’s hypothesis of elevation and Darwin’s of subsidence may
be applicable to certain cases, and, secondly, because a Pacific
continent in the sense of Hutton, Pilsbry and Baur cannot
evidently be cited in support of most of the older Tertiary
affinities between Asia and North America that I have alluded

* Speight, R., “ Petrological Notes on Rocks from Kermadec Islands,”
pp. 244—250.

+ Haug, E., “ Géosynclinaux et aires continentales,” p. 646.
{ Arldt, T., “ Parallelismus d. Kiisten y. Siidamerika.”’

328 ORIGIN OF LIFE IN AMERICA

to. If a Pacific continent existed, and I quite concur with
those who are of that opinion, it must have largely subsided
before the Tertiary Era. It seems to me as if the central
part of it had broken down gradually, the margins slowly
following suit, both on the eastern and western Pacific, only
leaving here and there a few remnants which either remain
as isolated pillars far out in the ocean or have become joined
to more recent land-masses. I imagine that the latest pre-
Pliocene land connection between North America and Asia was
not the Pacifie Continent, but merely its margin, which per-
sisted probably until Oligocene or Miocene times. In a geo-
logical sense, remarks Dr. von Drasche,* it is more correct
to draw the western boundary of the Pacific Ocean through
Kamchatka, Japan, the Philippines, New Guinea and New
Caledonia, because they all possess old crystalline or ancient
sedimentary rocks. But the oceans, as Professor Walther +
has pointed out, are areas of depression surrounded by folds or
flexures which give rise to extravasation of eruptive material.
The chain of the volcanic Aleutian islands lie in such a fold.
Near the east coast of Japan the depth greatly increases. On
the eastern side of the Pacific, in western North America,
the igneous rocks skirt the coast for some distance, whereas
in the south-west the volcanic centres lay far inland, justi-
fying the assumption that the Tertiary coast-line extended
some distance inland, which is fully established by geological
observation. Although the Pacific is known to have invaded
Californian territory, there is no evidence that the coast hills
and outlying islands were covered by the sea; and these pro-
bably remained as part of the marginal land which skirted the
west coast of North America. Itis from this old land, I think,
which contained Asiatic immigrants, that North America
received its ancient Tertiary fauna from Asia. I suggest,
therefore, that in early Tertiary times a belt of land, possibly
representing the margin of the more ancient Pacific Continent,
extended from the south-west coast of North America in a
great curve to Japan and further south (see Fig. 14). The
extraordinary similarity of the east Asiatic, Mesozoic and

_ * Drasche, R. von, “ Palaeozoische Schichten auf Kamtschatka,” p. 268.
+ Walther, J., “ Uber den Bau der Flexuren, &c.”’

if
|
ie

NORTH PACIFIC LAND BRIDGE 329

early Tertiary marine faunas to those of California would.
thus receive a satisfactory explanation without invoking a
land connection across Bering Strait. As soon as the marine
channel which separated the coast hills in California from the
rest of the country disappeared, a number of Asiatic immi-

‘grants entered North America. But the flora, especially of the

small islands lying off the coast of California, still bears the
impress, as Mr. Greene* has pointed out, of belonging phyto-
geographically to another continent than America.

I also mentioned that the European invasion of North
America, which travelled by the trans-Atlantic land bridge,
had ultimately entered the Continent from the south-west.
The two elements, the Asiatic and the European, must have
joined there eventually. To judge from purely faunistic testi-
mony, that was evidently the course of events (compare
p. 211). Somewhere about the Miocene Period extensive sub-
sidence of the land west of California must have compelled
the fauna and flora to seek refuge on the continent with which
the Pacific belt of land seems to have become united. Palaeon-
tological evidence gives us reason for such a supposition. Take
for example the great land-tortoises. Their sudden appearance
in south-western Miocene deposits suggests that they. came
from the west with other new-comers. This hypothesis like-
wise throws light on their survival near at hand in the Gala-
pagos islands, which no doubt once formed part of the Pacific
belt of land alluded to. There are such a variety of problems
connected with this theory that I shall defer the further dis-
cussion of it till the next chapter. In conclusion, a few addi-
tional remarks on the nature of the supposed extension of land
west of Central America will facilitate the comprehension of
the scheme of land connections that have only been roughly
outlined so far.

When I described the remarkable fauna and flora of the
Cape region of Lower California (p. 207) and their marked
affinities to those of the opposite coast of Mexico, I made no
reference to the fact that this interesting assemblage of
animals and plants is living in a hilly district being separated
from the nearest mountains to the north of it by a wide extent

* Greene, E. L., ‘‘ Botany of Santa Cruz Island,” pp. 377—3888.

330 ORIGIN OF LIFE IN AMERICA

of a low-lying plain. This district, moreover, is entirely
granitic and composed of a number of high ridges running
parallel in an east-westerly direction, the remainder of the
great peninsula being largely formed of calcareous rocks with
mountain ranges running in a north and south direction.
Between the two lies a great plain several hundred miles long
with a height of scarcely one hundred and fifty feet above sea-
level. The two mountain ranges manifestly belong to entirely
different systems, and the junction between the two must have
been a comparatively recent geological event. Mr. Hisen*
was so much impressed by the supposed severity of the climate
during the Glacial Epoch that he believed the whole Cape
region was at that time wrapped in snow and ice and devoid of
animal life. But he also contends that it must have been an
island and that during its rise animals and plants gradually
reached it from the mainland by accidental transport. That
the Cape Region has only recently become part of Lower Cali-
fornia is highly probable. To judge from the fauna and flora,
it must have been connected by land with some part of Central
America or southern Mexico, though it possesses affinities, too,
with Asia and the Pacific islands (compare, p. 208). Rather
more than half-way across the sea between the Cape Region
and the south coast of Mexico lies the small group of the
Tres Marias islands, and it might be argued that they
had once formed the connecting link between the mainland
and that faunistically so remarkable Cape Region of Lower
California. The animals and plants of these islands, how-
ever, although clearly showing that the islands have been
joined to one another and to southern Mexico, exhibit no
near relationship to those of the Cape Region. Hence it
is probable that the faunistic and floristic affinity between
the Cape Region and southern Mexico is due to the fact
that both regions have acquired their animals and plants, in
more remote times, from the same source in Central America.
I suggested in a former chapter (p. 237) that the moun-
tains of Guatemala had once extended further westward.
Guatemala certainly seems to have been a land surface

* Hisen, G., “ Explorations in the Cape Region,”’ p. 735.

+ Nelson, E. W., L. Stejneger, and others, “ Natural History of the
Tres Marias Islands.”

SUNKEN PACIFIC LAND 331

_ since very remote geological times, while its ancient moun-
tain system, trending in a west-eastward direction, abruptly
terminates on the Pacific coast. I ventured: to explain
the many instances of curiously discontinuous distribution
in Central America by the supposition that an ancient land
occupied the adjoining portion of the Pacific, and that the
present Central America is partly formed of the remnants of
that land having eventually become moulded together by geo-
logically recent voleanic deposits. If we assume that the Cape
Region of Lower California belonged to that Pacific land
which really formed the southern continuation of the north
Pacific belt of land alluded to, a reasonable explanation is
advanced for the faunistic affinity of the Cape Region to
Central America, the West Indies and Asia, and its dissimi-
larity with the rest of Lower California. The hypothesis of a
former westward continuation of portions of Central America
is not founded purely on zoogeographical considerations.
In his reference to the older Tertiary sediments of Central
America Professor Hill* states that it is impossible to avoid
the conclusion that they were derived from a near-by
land which existed at the time of their deposition. The only
hypothesis, he says, that can fit the condition of their
present lay and arrangement is that this land existed
towards the Pacific coast or in the area now covered by the
Pacific waters of the Isthmian Region. The “old land”
or early representative of the isthmus of Panama, remarks
Mr. Hershey,+ lay mainly south of the present isthmus.
That it was a land-mass of considerable extent, he con-
tinues, is indicated by the heavy beds of conglomerate
formed from it, and he argues that the peninsula of Azuero
which projects out into the Pacific is a remnant of this land,
while on its northern border were laid down the more recent
formations which make up the main body of the isthmus.
Geologically there is, therefore, some evidence, too, for the
assumption of a former extensive land surface on the Pacific
side of Central America. It must be remembered that while
Central America as a whole has a south-east and north-west

* Hill, R. T., “Geological History of Panama,” -p. 263.
+ Hershey, O. H., “Geology of Isthmus of Panama,” p. 249,

332 ORIGIN OF LIFE IN AMERICA

trend the isthmus of Panama runs in an east-westward direc-
tion. :

That this Pacific land persisted to some extent until com-
paratively recent geological times, seems to be indicated by
several notable features. When Mr. Agassiz surveyed the
ocean floor from the steamer ‘‘ Albatross,” he found the Pacific
side of Panama faunistically poor compared with the Atlantic
side, but he attributed that condition to the absence of a great
oceanic current on the south side of the isthmus. The absence
of deep-sea corals on the Pacific side was most striking. Yet,
he remarks that there is on the west coast of Central America,
even in deep water, a considerable fauna, which finds its
parallel in the West Indies and recalls later Cretaceous times
when the Caribbean Sea was practically a bay of the Pacific.
This assumption that the Caribbean Sea was once a bay of
the Pacific has been put forward by other writers. The
faunistic resemblance, or parallelism, as we might call it,
between the seas on each side of Central America may be due
to a former westward extension of the Atlantic Ocean just
as much as to an eastward extension of the Pacific. However,
one of the most remarkable features brought to light by the
“ Albatross” expedition was the condition of the ocean
floor. There was not a station between Acapulco, on the
coast of Mexico, and the Galapagos islands, according to
Mr. Agassiz, of which the bottom could be characterised as
strictly oceanic. At the most distant points from the
shore the bottom specimens invariably showed some trace of
admixture of terrigenous material. All the way, even to a
depth of 2,000 fathoms, the trawl became filled with a sticky
mud containing logs of wood, branches, twigs and decayed
vegetable matter. Being a firm believer in the permanence
of ocean basins, Mr. Agassiz * naturally attributed this extra-
ordinary condition of the sea floor to the existence of currents,
which, striking Central America from north and south, are
reflected in a westward direction. He likewise argues from
this discovery that it offers a very practical object lesson re-
garding the manner in which the Galapagos islands received
their fauna and flora. The peculiar condition of the ocean

* Agassiz, A., “ Reports on ‘ Albatross’ - Expedition,” pp. 11—77.

AFFINITIES OF TWO OCEANS 338

floor may, I think, be explained in an entirely different way.
We might possibly expect. a condition such as Mr. Agassiz
describes off the mouths of the Amazon or Orinoco rivers, but
there are no vast rivers anywhere on the Pacific coast to fur-
nish all this vegetable detritus he speaks of. A similar condi-
tion, moreover, occurs only to a very limited extent on the
Atlantic side of the isthmus. That the ocean floor is covered
with tree trunks, twigs and other vegetable detritus may be
due to the existence within recent geological times of a well-
timbered land between Central America and the Galapagos
islands which has since vanished beneath the ocean.

_ And yet that all was not land on the Pacific side of Central
America is proved by many distinct lines of evidence. |

Mr. Guppy * tells us that Laguncularia racemosa, Rhizo-
phora mangle, Anona paludosa and Conocarpus erectus, all
of which are plants of the mangrove formation, occur not
only on the Pacific and Atlantic coasts of America, but also
on the west coast of Africa. We cannot suppose that such
characteristic sea-shore species can be conveyed across a land
area by any known means of accidental dispersal. Moreover,
since that vegetation does not occur south of the Bay of Guaya-
quil, it could not have reached the coast of Ecuador from
eastern South America by travelling round Cape Horn. Thus
the most likely explanation of the occurrence of the flora on
both sides of Central America is to assume the existence of
a former continuous shore line between Ecuador and Vene-
zuela.

In the list of stalk-eyed crustacea found on the coast of
Peru, Miss Rathbun + reports that a few species of crabs, like
Acanthonyx petiverii, Microphrys platysoma, Panopeus ber-
mudensis and Geograpsus lividus, are common to both sides
of Central America, while a most striking feature is the
faunistic uniformity of the marine area between the Cape
Region of Lower California and the coast of Chile. Dr.
Dall{ divided this whole fauna into two provinces, viz., the
Panamic, extending from Lower California to Guayaquil, and
the Peruvian, from the latter to the island of Chiloé in Chile,

* Guppy, H. B., “ A Naturalist in the Pacific,” p. 498.

+ Rathbun, M. J., “Stalk-eyed Crustacea of Peru.”
t Dall, W. H., “ Report on the Shells of Peru,” p. 185.

334 ORIGIN OF LIFE IN AMERICA

but the two have many forms of mollusks in common, and
should be regarded perhaps as sub-divisions of one faunistic
marine area. According to Dr. von Ihering,* Chile received,
in early Tertiary times, certain tropical genera of mollusks
which never succeeded in attaining the North American
coasts, yet are represented also in Patagonia, while others,
such as Conus, Purpura, Oliva, Concholepas, Cassis, Cypraea
and Rissoa are absent from the latter country. They are
supposed to have travelled along the north coast of South
America to Ecuador, Peru and Chile by means of a Central
American marine channel. Certain species even of that an-
cient marine migration have persisted to the present day,
not only on the coast of Chile, but on the west coast of Africa
and in the Mediterranean. Even in Miocene times the in-
fluence of the Caribbean and European marine faunas was
felt on the coast of Peru, according to Dr. Ortmann.t+
Certain northern species of the genera Saxidomus and
Chlorostoma, says Dr. von Ihering (p. 524) did not reach the
coast of Chile until the Pleistocene Period. Thus it seems
manifest that during practically the whole of the Tertiary
Kra there was no Humboldt current sweeping northward
along the west coast of South America, as it does at present.
On the contrary, there is sufficient evidence to show that
whatever current there existed flowed in the opposite
direction.

This investigation has resulted in two very important
results, viz., firstly, the demonstration that the Humboldt
current formerly did not exist, and secondly, that its absence
must have been caused by profound differences in the condi-
tions of land and water from those now prevailing. Of the
nature of these changes I have foreshadowed already enough
to enable anyone to reconstruct them. When the currents
issued from the Caribbean Sea into what is now the Pacific,
they must have been faced by land westward and northward.
They could only have flowed southward. But the land which
lay south-westward between Central America and the Gala-
pagos islands extended probably far southward, parallel to

* Thering, H. von, “ Mollusques fossiles de Argentine,”’ pp. 514—516.
t+ Ortmann, A. E., “ Tertiary Invertebrates of Sta. Cruz,” p. 320.

ete hd ee Na peste
a hore Noa a pit Path me
ep Mery Kee ee hy dz

2 oe

Piste ee
=

rw

HUMBOLDT CURRENT 85

THE HI
the present coast. How far it reached will be more fully dis-
cussed in the subsequent chapters. It may only compara-
tively recently have subsided. May not the remarkable cir-
cumstance, alluded to by Dr. Bigelow,* that to the south-west
and west of the Humboldt current the sea is almost entirely

- devoid of surface as well as bottom life, be due to this

cause ?

* Bigelow, H. B., “ Albatross Expedition—Medusae,” p. 222.

Da ee hire he a TO I Le OF CITT ee Mike aI Pere 2 LA
No A eo Oe Ee : et ele 1 or 4 Ee SEND fe 0

r Lao
Pea thy
+
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CHAPTER XIII

NORTHERN STATES OF SOUTH AMERICA

THE great continent of South America (Fig. 18), with its
roughly triangular shape, is not much smaller than its
northern relative. The basis of the triangle facing northward
is bounded by the Caribbean Sea, and the two other sides
by the Atlantic and Pacific Oceans respectively. There is
a very general impression that the west coast of South
America is mountainous, the remainder being a vast plain.
This is not quite correct. A northern continuation of
the long chain of the Andes skirts also the southern shores
of the Caribbean Sea, while to the south-east of it lies the
highland of Guiana and further south the Brazilian highland.
The two eastern highlands—that of Guiana and Brazil—are
broken into two parts by the Amazon valley. The space
between these eastern highlands and the Andes is occupied
by the central lowlands. We might say, therefore, that the
three great natural regions of South America are the eastern
highlands, the central lowlands and the western Cordillera.
The Amazon, Orinoco and La Plata—the three great streams
—all drain eastward. ,

The main part of the continent has a tropical climate.
Sub-tropical and temperate conditions prevail in the south.
The climate of the Brazilian region is exceptionally favour-
able for a luxuriant development of the fauna and flora,
whereas certain parts of what Dr. Wallace called “ the Chilean
sub-region ’’ are arid, and inimical to expansion and specific
differentiation of animals and plants.

Although our acquaintance with the fauna, flora and
geology of this vast continent is naturally much less complete
than that of North America or Hurope, we possess unmis-
takable evidences of the fact that South America has under-
gone considerable alterations in the distribution of land and

i]
— oe eee ee

om °
. PeGalli nas ye 10

2

45

=> Highland over 1500 Ft
Upland over 600 Ft

Gaze Lowland under600Ft
3b

6U

Fic. 18.—Map of South America. (Reproduced from Meiklejohn’s Oroscopic
Map, by permission of Messrs. Meiklejohn & Son.)

[ Zo face p. 336.

HISTORY OF SOUTH AMERICA 387

water since the close of the Mesozoic Era. The testimony is
of a threefold character. It is founded on our knowledge of
geology, of palaeontology, and of the geographical distribu-
tion of living animals and plants. Richness, as Dr. Wallace
observed, combined with isolation, is the predominant feature
of neotropical zoology. Nevertheless, he thinks that early
during the Tertiary Era, the zoological differences between
the Nearctic and Neotropical, that is to say, between the North
and South American regions, were probably even more radical
than they are now. South America, he argues, was then a
huge island or group of islands—a kind of Australia of the
New World—chiefly inhabited by the imperfectly organised
group of edentate mammals. Dr. Wallace * believes, more-
over, that there must have been one or more ancient land
connections between the two continents, perhaps in Eocene
or Miocene times, admitting ancestral types of monkeys and
the members of the camel-tribe (Llamas) from the north to
South America.

Dr. Wallace’s. opinions, expressed thirty-five years ago,
were founded entirely on the distribution of living animals.
Rapid strides have been made since that time in our know-
ledge of the fauna of South America. The geology of. certain
districts is being worked out. Botanists have made great
progress in mapping out the distribution of plants, while the
most astonishing discoveries have been disclosed principally
among the past inhabitants of the continent. Thus we are
now in a very different position from that of Wallace, when
he pronounced upon the physical changes of South America
during the past, on the strength of his zoological know-
ledge. |
We are particularly indebted to Dr. von Ihering’s re-
searches on the fauna and flora of South America, which he
conducted during many years of devoted labour, that our in-
formation on the main features of distribution has advanced
so rapidly. During his long residence in southern Brazil he
collected, and is still collecting, data bearing principally on
the question of the geological history of the continent; and
since his scattered papers have recently been reprinted in

* Wallace, A. R., ‘ Distribution of Animals,’’ IT., p, 48.
L.A. VA

338 ORIGIN OF LIFE IN AMERICA

book form we are better able to appreciate the advances in our
knowledge that are due to his investigations. His researches
were not confined to recent zoology. He has also dealt with
the subject from a palaeontological point of view, and has
even subjected the main features of the flora to a detailed
revision. All the same, he acknowledges that there are several
important problems connected with the geological history of
South America for which no satisfactory solution has as yet
been suggested. More than twenty years ago, Dr. von Ihering
announced that the close relationship of the Brazilian with
the African fresh-water mussels implied the former existence
of a land connection between South America and Africa.
But, whereas America as a whole is one of the richest regions
for fresh-water mussels in the world, Chile and Peru are
among the poorest. While east of the Andes there is a
luxuriant fauna of fresh-water mussels largely related to that
of Africa, we find only the genus Unio (in its wide sense) re-
presented on the western slope of the mountains. Dr. von
Ihering explains this and other similar facts by the supposi-
tion that in the east and the west there were originally similar
faunas, but while eastern South America obtained a rich stock
of immigrants across the land bridge from Africa, the great
mountain chain of the Andes, which was then commencing
to rise, prevented any further influx westward. Considering
that the fresh-water mussels (Unionidae) are well represented
even in Jurassic deposits, Dr. von Ihering* recognised that the
geographical distribution of these mollusks may be utilised
to advantage as indicators of very ancient, especially
Mesozoic, conditions of land and water.

In the course of his studies the same author came to the
conclusion that from the Cretaceous to the end of the Pliocene
Periods, South America must have been completely separated
from North America. A real South American continent
existed only since Oligocene times. It then consisted of two
parts united by the narrow isthmus of the newly formed
Andes. He named these two old original constituents of
South America ‘“Archiguiana’”’ and ‘‘ Archiplata.’”? The
former comprised the highlands of Guiana and Venezuela,

* Thering, H. von, ‘‘ Archhelenis and Archinotis,’’ p. 79.

FAUNISTIC ELEMENTS © 339

the latter the remainder of South America, the two parts
being separated by a broad ocean except for a narrow western
land bridge. Each of these great islands had its own peculiar
fauna and flora, but Archiguiana must have been connected
by land with Africa until Oligocene times, and Archiplata
with New Zealand and si pvr during the ee
Era. ee

With the gradually increasing knowledge of ‘pak aos
Dr. von Ihering’s original ideas naturally became subject to
various modifications. Thus in a map representing the con-
ditions of land and water during the Hocene Period, and pub-
lished in 1907 (Fig. 17), not Archiguiana but Archiplata is
connected by land with Africa and also India, the whole of
this ancient continent being called “‘Archhelenis.’’ Archi-
plata is still joined at this time to Australia by means of the
antarctic continent ‘‘Archinotis,’’ while Arehiguiana is
united with the West Indies and parts of Central America
into a large land-mass which stretched forth westward to the
Sandwich islands, and was called “ Pacila.” Quite recently
the same author brought forward testimony in favour of a
Miocene land bridge between Central America and eastern
Asia. I have already alluded to it in the previous chapter.
Dr. von Ihering now tells me that he will shortly publish
a revised palaeogeographical map in the ‘‘ Neues Jahrbuch
fir Mineralogie und Geologie,” in which these features are
indicated.

The same problem, studied from the point of view of the
distribution of fresh-water crabs and crayfishes, led Dr.
Ortmann* to somewhat different conclusions. At the end
of the Mesozoic Hra he recognises the existence of the island
of Brazil, which had previously been connected with Africa,
while Guiana was still joined to western North America on the
one hand and Africa on the other. The independent Chilean
tract of land was connected with Australia by means of the
supposed antarctic continent (Fig. 15). At the commence-
ment of the Tertiary Era South America had assumed its
present shape, except for an elongated bay extending inland
from the Atlantic Ocean into the valley of the Amazon. In

+ Ortmann, A. E., “ Distribution of Decapods,” pp. 379—381.
Zz 2

340 ORIGIN OF LIFE IN AMERICA

the south it was still joined to the Antarctic Continent, which
had then become separated from Australia. In the north it
had lost its land connection with North America, which it did
not regain until later Tertiary times.

To a certain extent the views of the two authors agree, at
any rate, in the assumption that the continent of South
America is composed of several originally independent land-
masses, one of which was joined to Africa. The most striking
difference in their opinions, apart from the geological period
during which the various elements are supposed to have be-
come fused together, lies in Dr. Ortmann’s conception of
three totally distinct land-masses, while Dr. von Ihering only
recognises two. Nevertheless, even the latter acknowledges
the faunistic division of his “‘ Archiplata ’’ into a northern
and southern portion, although his nomenclature is apt to be
somewhat confusing. Dr. von Ihering informs us (p. 177)
that the old Archiplata fauna has no close relationship to
that of the rest of South America.

A third contribution to the geological history of South
America is furnished by another group of fresh-water animals,
namely, the fishes. The tropical American fresh-water fauna,
having its centre of greatest diversity in the middle Amazon
basin, says Professor Kigenmann,* is attenuated northward
till it reaches the vanishing point just on the borders of
the United States. Southward it extends to somewhere south
of Buenos Aires. The Patagonian and North American
faunas are entirely different from the tropical American fauna
and from each other. The results of his studies are that the
existing distribution of the fresh-water fishes can only have
been brought about by the supposition that tropical America
in early Tertiary times consisted of two land areas (‘‘ Archi-
guiana ’’ and “‘ Archamazona ’’), separated by the lower valley
of the Amazon, which was submerged by the sea. There was

a land-mass between Africa and South America, possibly
joining Guiana and tropical Africa. But this connection, he
urges, must have ceased to exist before the origin of the
present genera, and even before that of some of the families.

* HKigenmann, 0. H., ‘‘ Freshwater Fishes of South America,” pp.1517
—528.

+
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Pe 5-2

GEOLOGY OF SOUTH AMERICA 341

Several other writers have discussed the theory of former
land bridges between South America and Africa and between
South America and other continents without dealing with the
geological history of South America itself. Their views will
be presented later on.

The only author who, to my knowledge, has treated the
subject under review from a purely palaeontological stand-
point is Dr. Ameghino. His views were brought for-
ward in several important technical papers. As they may
have undergone slight modification in the course of time, I
prefer to quote his opinions from a recent semi-popular
account. It may be mentioned that Dr. Ameghino’s *
theories are founded on the known distribution of fossil
mammals. North of the Equator, he says, there was, at the
end of the Mesozoic Era, a vast ocean containing many
islands. In the south lay a great continent, united in the
east with Africa and in the south with Australia and New
Zealand by way of an antarctic land bridge. Gradually, in
early Tertiary times, the northern islands became fused and
joined to the southern land-mass, while Australia was dis-
connected. During all this time North and South America
remained entirely separated. Mammals, however, were able
to pass from the latter continent through Africa into Europe,
and across a land bridge in northern latitudes to North
America. The sea, which had covered the Andean region in
Mesozoic times, disappeared early in the Tertiary Era, but
certain bays of the Pacific Ocean still remained and ex-
tended eastward to the far side of the Andes. During the
Kocene Period the Atlantic Ocean advanced from the south,
covering part of Argentina and practically separating

- Brazil from the rest of the continent, while the former land

connection with Africa ceased to exist. Towards the end of
the Oligocene Period the ‘‘Archhelenis”’ land bridge once
more rose to the surface for a brief period and then finally
subsided entirely, save for a few scattered islands.

It would have been particularly valuable to obtain Pro-.
fessor Osborn’s opinions on the geological evolution of South

_ America. We possess only his palaeogeographical maps

* Ameghino, Fl., “ Geologia de la Repaiblica Argentina,” pp. 9—16.

342 ORIGIN OF LIFE -IN AMERICA

founded upon the distribution of fossil mammals. It is sur-
prising that in these maps South America in late Cretaceous
and basal Hocene times, is represented as almost precisely
what it is to-day, except that it is continued southward across
an antarctic continent to Australia. In the middle Eocene,
South America differs only in so far as a long bay of the
Atlantic has entered the Amazon valley. There are no indica-
tions of any land bridges at that time, South America being
completely isolated from all other continents. During the
Oligocene Period it still remained so, but the sea made
further inroads on the Amazon valley, it encroached on the
valley of the Parana river and flooded a large part of Argen-
tina, reducing southern Chile to a few islands. It is only in
Miocene times, according to Professor Osborn,* that South
America became divided into two parts by a broad gulf ex-
tending from the Atlantic to the Pacific across the Amazon
valley.

Geologists, except Dr. Katzer and Professor de Lapparent,+
have as a rule dealt with the problem in a less comprehensive
manner. The ideas of the latter differ from the authors cited
in so far as the main permanent land-mass at the end of the
Mesozoic Era in South America was confined, in their opinion,
to the east. They suppose the highlands of Guiana, eastern
and southern Brazil to have been united. All the rest of the
continent was then under water. At the commencement of
the Hocene Period, according to Professor de Lapparent,
Central America had come into existence, but disappeared
again shortly after, while a broad marine channel stretched
from the Pacific to the Atlantic between northern Chile and
Argentina. Dr. Katzer’s views are somewhat similar. He
dces not believe in the Atlantic Ocean having invaded South
America from the east. In the beginning of the Mesozoic Era
the area of archaean rocks and later palaeozoic deposits of
Guiana and Brazil formed a large connected land-mass. In
Upper Jurassic times, he says, the old land connection be-
tween South America and South Africa on the one hand, and
between South America and Australia, still existed. An old

* Osborn, H. F., “‘ Age of Mammals’? Maps, pp. 64, 137, 183 and 244.
+ Lapparent, A. de, “'Traité de Géologie,”’ 4th ed., pp. 1376 and 1445.

DEVELOPMENT OF SOUTH AMERICA 343

ocean strait extended from the north side of Guiana across
Venezuela and Colombia to Peru during the Cretaceous
Period. During all this time, and even in early Tertiary
times, the waters from the old eastern land continued to
drain westward towards the Pacific. The persistent rise of
the newly formed Andean mountain chain resulted at first
in the formation of a vast lake covering the entire Jowlands
of the Amazon valley area. Eventually, in Miocene times,
according to Dr. Katzer,* the drainage was reversed, with the
result that the Amazon river flowed for the first time into the
Atlantic Ocean. Concurrently North and South America be-
came united through the Central American land bridge.

Professor Koken’s + palaeogeographical maps were con-
structed as the outcome of a combination of geological and
palaeontological studies. South America, he remarks, had
already assumed its present shape and form in Cretaceous
times, though it did not extend so far west as at present except
in Ecuador and Colombia. It was separated from all other
continents but Africa. In early Tertiary times South America
became entirely isolated. Argentina and southern Chile were
largely flooded by, the sea, while a long gulf filled the whole
valley of the Amazon as far east as the Andes.

Dr. Arldt,{ who included the distribution of living animals
and plants as well as palaeontology within the sphere of his
studies, gives a series of highly complex maps which cannot
readily be described. His conception is that South America
in Lower Cretaceous times was somewhat like that described
by Professor Koken, viz., an extension of land eastward as far
as Africa and a simultaneous submergence of the west coast.
Towards the end of the Mesozoic Era, that is to say at the end
of the Cretaceous Period, a complete change in the conditions
of land and water supervened. South America was then
divided into two parts by an interoceanic connection across
the Amazon valley. The northern portion, consisting of
Colombia, Ecuador and Guiana, is supposed to have extended
westward across the Galapagos islands as far as the Sandwich

* Katzer, F., ‘‘ Geologie des Amazonengebietes,” pp. 239—262.
+ Koken, E., ‘“‘ Die Vorwelt,”? Maps 1 and 2.
¢ Arldt, J., ‘‘ Entwicklung der Kontinente,” Maps 19 and 20.

344 ORIGIN OF LIFE IN AMERICA

islands, thus forming a great peninsula of land which like-
wise was joined to lower California and western Mexico. The
southern part of South America was then still united by a
narrow land bridge with Africa, while the western side of it
now became joined to a great belt of land extending right
across the Pacific Ocean to New Zealand and Australia. In
early Tertiary times South America became separated from
North America and the Sandwich islands, while the two
sections of the continent fused in the west. The African
and Australian land connections still persisted in a modified
form.

We can gather from all these expressions of opinion as to
the past geological history of South America that there is
comparatively little general agreement on the subject. Some
points, however, seem to be fairly well established. All
authorities concur in the belief that the Eastern highlands of
Guiana and Brazil have been land surfaces since the begin-
ning of the Secondary Era, at any rate, and on these, there-
fore, we ought to find relicts of a Mesozoic fauna. All the
writers quoted also agree that at some time or other during
the Tertiary Era there was either a complete interoceanic
connection along the Amazon valley or a long gulf of the ocean
extending for some distance inland. Yet there is an im-
portant difference of opinion as to whether this gulf belonged
to the Atlantic or the Pacific Ocean. But since most of the
writers contend that the central portion, at any rate, of the
Andes is made up largely of Jurassic and Cretaceous marine
deposits, while the eastern parts of South America were land
in Mesozoic times, it seems more reasonable to assume, with
Dr. Katzer, that the Pacific Ocean extended eastward as far
as the archaean highlands of Brazil and eventually retreated
so as to leave only a Pacific gulf on the site of the existing
upper Amazon valley. In view, however, of the fact that the
Pacific Ocean must have been completely shut out from South
America by the western belt of land above alluded to, it was

really the waters of the Atlantic Ocean which flooded western |

South America as far east as the highlands of Brazil (com-

pare Fig. 14).

| Several of the authors cited recognise a faunistic relation-
ship between Australia as well as between Africa and South

ee ee ae

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DEVELOPMENT OF SOUTH AMERICA 345

America, and some contend that Chile has been wholly or par-
tially above the surface of the ocean since very early geological
times. As Professor Suess * has pointed out, the extreme
south of the continent is composed of a peculiar and probably
very ancient system of rocks. This Patagonian mountain
chain is quite independent of the Andes, of which it does not
form a continuation. Further north in Chile it lies outside or
westward of the Andes, constituting the coast Cordillera.

Still further north, in Peru, only fragments of this Cor-
dillera are recognisable here and there close to the coast,
while in Ecuador the ancient coast Cordillera again appears
to be more clearly represented. There is some evidence,
therefore, of the existence of a very old land-mass not only on
the eastern but also on the western side of the continent. And
it seems as if the Mesozoic rocks forming a large part of the
Andes had been deposited in a great trough along the eastern
shores of this ancient land. When the Andes were subse-
quently raised, the older western land presumably subsided,
leaving only here and there along the coast some traces of its
former existence. |

Let us now pursue this subject from a purely zoogeo-
graphical point of view, and endeavour to utilise groups with
whose distribution we are fairly well acquainted, in elucida-
ting the more obscure points in the geological history of
northern South America. Groups of animals of which we
have reason to believe that they are very ancient, possibly
of Mesozoic age, will be best for this purpose. Such a one for
example is that of the Onychophora (Protracheata). It
contains creatures caterpillar-like in appearance, with a beau-
tifully soft skin and unjointed limbs. Internally they contain
air-tubes so characteristic of insects ; at the same time, their
excretary organs resemble those of worms. These very pri-
mitive features, taken together with a wide and most discon-
tinuous distribution, have always caused these creatures to
be looked upon as survivors or relicts of very remote geological
ages. Formerly they were all classified under the genus
Peripatus. In recent years many new forms have been dis-
covered and subjected to careful study, with the result that

* Suess, E., “‘ Antlitz der Erde,” I., pp. 666—690.

346 ORIGIN OFj-LIFE IN AMERICA

quite a number of genera are now recognised. The most
exhaustive account of these remarkable creatures.is, no doubt,
the monograph recently published by Professor Bouvier. He
divides the group into seven genera, of which Peripatus is
confined to tropical and sub-tropical America and tropical
Africa, and Opisthopatus to Chile and South Africa. This is
a most astounding discovery. That a group of these creatures
found in tropical South America should be more closely related
to another occurring in tropical Africa than to that of Chile,
and that the latter should exhibit a more intimate affinity with
South African forms than with tropical American ones, is of
great zoogeographical interest. Professor Sedgwick,* however,
does not share Professor Bouvier’s opinion with regard to
the intimate relationship supposed to exist between the
tropical South American and tropical African, and between
the Chilean and South African groups. He thinks they are
perfectly distinct from one another. On the other hand, he
agrees with Professor Bouvier in the recognition of a group of
Onychophora, limited to tropical and sub-tropical America, as
distinct from the Chilean group. And this is really the prin-
cipal point I wish to draw attention to.

Professor Bouvier; claims that the Andean species of Peri-
patus are the most primitive members of the whole family.
He believes that the ancestral stock inhabited a former Pacific
continent, and that their immediate descendants took refuge
on the eastern and western land areas when their original
habitat vanished. The whole genus Peripatus, as defined by
Professor Bouvier, | may mention again, is found from
Mexico in the north, throughout Central America, the West
Indies and South America as far south as Bolivia. The
Chilean species belongs, according to the same authority, to
the distinct genus Opisthopatus.

The genus Peripatus is readily divisible into two sections,
the Andean and the Caribbean one. The twelve species be-
longing to the former all inhabit the Pacific side of the Andes,
except Peripatus eiseni and Peripatus goudoti, which live in
Mexico nearly two thousand miles north-westward of the other

* Sedgwick, A., ‘‘ Distribution of Onychophora,” pp. 383—406.
+ Bouvier, E. L., ‘“‘ Onychophores,” I., pp. 64—79.

PERIPATUS IN SOUTH AMERICA 847

members of the Andean group. This discontinuous distribu-
tion is a very noteworthy fact, for it cannot be explained by
the supposition that some member of this Andean group may
still exist and have been overlooked in the intermediate vast
tract of country, because many specimens of Peripatus have
been discovered in Costa Rica, Nicaragua and Panama, all
belonging to the Caribbean group. Accidental dispersal, such
as marine currents, cannot be invoked as being responsible for
this distribution. It is due, in my opinion, to a former direct
land connection between western Mexico or Guatemala and
some part of the west coast of South America. That the
mountain system of Guatemala suddenly terminates at the
edge of the Pacific, and that it formerly had a westward
continuation, has been alluded to, and I have mentioned also
several cases of discontinuous distribution that I thought
were due to the existence of an ancient land, more or less in-
dependent of Central America. The newt Spelerpes is one
of these. Its headquarters seem to be in Mexico. A few occur
in Guatemala, Costa Rica and Chiriqui. Further south we
meet with the genus again in Colombia, Heuador and northern
Peru, but nowhere else in South America. The tortoise
Chelydra rosignoni occurs in Guatemala. It is absent from
the rest of Central America, yet in Ecuador we find an isolated
colony. Another tortoise, Geoemyda punctularia, inhabits
Guatemala and Mexico. Southward it is only known from
Ecuador, Colombia, Venezuela and further east. The gecko-
like genus Eublepharus is probably an exceedingly ancient
one, its range being most peculiar and strikingly western.
One species occurs in California, another in Mexico, still
another in Panama, and lastly one in Keuador. All the re-
maining species, which show great resemblance to the
American ones, are confined to southern Asia. We probably
have to deal in this case with a persistent type which through-
out many geological periods has retained the same characters
and has died out in the still existing land fragments of the
ancient Pacific continent, whence it originally spread east
and west after its subsidence. There are numerous other
examples, particularly among plants, implying that the land
which I described as lying westward of Central America
once touched the South American continent, probably near

348 ORIGIN OF LIFE IN AMERICA

Ecuador (compare Fig. 14). As this western belt of land
was in direct communication with the West Indies by way
of Central America, it follows that the West Indies and
Ecuador were able to enter into a faunistic exchange. Many
instances might be quoted showing this relationship between -
the West Indies, Central America and western South
America, or between parts of these areas. The head-
quarters of the snake-like limbless amphibians, known as
Coecilia, are in Ecuador. From there they have spread
eastward through Guiana to Brazil, and northward through
Colombia as far as Panama. No species is actually known
to occur in Central America beyond Panama. I alluded
to the family Anguidae on several occasions, those generally
limbless lizards to which the so-called glass-snake belongs.
~ One genus with well-developed limbs (Diploglossus), inhabits
chiefly the principal islands of the West Indies, viz., Cuba,
Haiti and Jamaica. In Central America it occurs in Guate-
mala and Costa Rica, while in South America it inhabits only
Ecuador and Brazil, having apparently spread into the latter
state from the west.

Attention has been drawn to the fact that while the fauna
and flora of the Galapagos islands are principally Central
American and West Indian in character, they also are related
to those of western South America. A mere fragment only
of the animals and plants that passed across the lands of
which these islands formed part could have been preserved
there. Thus the Streptaxidae, a family of carnivorous snails
almost restricted in America to the southern continent, do
not occur in the Galapagos islands, although a few species
have penetrated to Guatemala, and one even to Haiti. The
genus Martinella is peculiar to Ecuador, whereas two other
genera, viz., Guestieria and Systrophia appear to have spread
from an HKecuadorian centre of dispersal to Peru, Colombia
and Bolivia.

A most interesting and important case of discontinuous dis-
tribution is that of Clausilia, a genus of snails which I men-
tioned when dealing with the origin of the West Indian fauna
(p. 272). I then stated the reasons for my belief that
Clausilia had travelled across the mid-Atlantic land bridge
from southern Europe to the West Indies rather than by a

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ON THE ORIGIN OF CLAUSILIA 349

land connection between eastern Asia and Central America
as suggested by Dr. von Ihering.* The American species
all belong to the sub-genus Nenia, being extremely like the
Pyrenean Clausilia pauli. So far only a single species is
known from the West Indies, while the genus has not
yet been discovered in Central America (Fig. 19). No
trace of Clausilia, either recent or fossil, has been met with
in North America or in northern Asia. If we assume that
Clausilia passed across the Atlantic Ocean to the West Indies
and thence to South America, it should have traversed Central
America. It may still be found in Guatemala, or it may
recently have become extinct. At any rate, I think it passed
from Central America to the western or Pacific land bridge con-
necting Guatemala with Heuador. The latter state, together
with northern Peru, must be looked upon as the centre of
dispersal of the South American species of Clausilia. Over
fifty Clausilias are now known from South America.t A few
are found northward of Ecuador as far as the province of
Bogota in Colombia. The great mass, however, is confined to
the highlands of Ecuador and Peru. South of Bolivia the
genus is unknown. Is there any possible explanation for the
presence of this isolated colony of mountain snails in western
South America except by migration on a former land connec-
tion from Europe or eastern Asia ? A dispersal of the ances-
tral Clausilia in early Tertiary times to South America by
_ means of either land bridge is possible, but I greatly favour
| the Atlantic one (compare Fig. 14). It also explains the
| presence of a species of Clausilia in Portorico better than the

| 4 other theory.

Besides this instance of discontinuous distribution, we more -
over have a large number of others exhibiting ancient rela-
tionship between the faunas of the west coasts of North and
South America. These will be more fully dealt with when we
come to the consideration of the Chilean fauna. I may only
mention one example, that of the three very closely related
genera of scorpions, Hadrurus, Hadruroides and Caraboc-
tonus. The first inhabits California, having spread from there

* Thering, H. von, ‘‘ Verbreitung der Heliciden,” p. 450.
+ Boettger, O., ‘Die Nenia Arten.”

350 ORIGIN OF LIFE IN AMERICA

into the adjoining state of Arizona. The second lives in
Ecuador and Peru. The third is only met with in Chile and
southern Peru. They all are entirely confined to the west
coasts. A somewhat more distant relationship exists between
the centipede Newportia of the West Indies and Central and
South America, and Plutonium, which is confined to Sardinia
and Corsica. This affinity implies the presence of a former
mid-Atlantic land bridge between the Mediterranean and
Antillean Regions and between the latter and northern South
America.

My principal aim, in alluding to the fauna of Ecuador
and the adjoining areas, was to point out the more im-
portant features of the former as an ancient land-mass
somewhat independent from the rest of South America,
and the affinity of its animal inhabitants with those
of Central America, the Antilles and even southern
Europe. The antiquity of the region can be demonstrated by
many examples. Even birds show it clearly. Among one
hundred and eighteen genera of humming-birds (Trochilidae)
known to science, Androdon, Eutoxeres, Damophila, Uro-
chroa, Phaeolaema, Agapeta, Ionolaema, Kugenia and others
are quite confined to this region.* Among mammals I need
only mention the remarkable discovery by Mr. Oldfield
Thomas + of Caenolestes. This small rat-like mammal in-
habits Ecuador and the province of Bogota in the adjoining
State of Colombia. It is, therefore, quite confined to north-
western South America. The only other known genera of the
family Epanorthidae were found in the Santa Cruz deposits
of Argentina. The presence of a still living member of this
otherwise extinct family is of considerable interest. Even
more important is the fact that Caenolestes is the only living
American herbivorous marsupial mammal more nearly related
to the kangaroo of Australia than to the American representa-
tives of the order—the opossums. .

The only South American representative of the family of
bears (Ursidae) known as the spectacled bear (‘Tremarctos
ornatus), on account of the yellow rings surrounding its eyes,

* Hartert, E., “ Trochilidae.’’
+ Thomas, O., “ On Caenolestes.”*

THE BEAR OF SOUTH AMERICA 351

is confined to the Andes between Colombia and Chile, that is
to say, altogether to western South America. This range sug-
gests that the bears are not originally a South American family,
otherwise we might expect their having a wider distribution.
The only alternative is that they migrated from some other
part of the world to the part of South America where they
still maintain themselves. Dr. von Ihering * argued that the
ancestors of the South American bear originally came from
Asia, and that they wandered across on a Miocene land con-
nection which united eastern Asia with Central America with-
out touching North America. In that case they would be older
than the North American bears which, according to Professor
Osborn,+ belong to the much later Pleistocene Eurasiatic inva-
sion. As a matter of fact, the geological history of the bears in
America has never received the careful attention it deserves.
Bears, it is well known, are entirely absent from Africa south
of the Sahara, that is to say, from what is known as the
Kthiopian Region, and no fossil remains of any members of
the family have ever been discovered there. Hence it is un-
likely that Africa was the source of the Ursidae or that they
invaded South America by means of a direct land bridge from
that continent as suggested by Dr. Ameghino.{ The absence
of bears from the whole of eastern South America indicates,
moreover, that bears have made their, entry from the west. The
bears of South and North America are not closely related.
They appertain to different genera. A fossil bear (Arcto-
therium vetustus), belonging to a genus closely related to or
identical with Tremarctos, has been recorded by Dr. Ameghino
from the Hntrerios deposits of Argentina which are of Mio-
cene age. It would appear on that account as if Dr. von
Thering’s suggestion that the South American bears were older
than the North American ones, and had quite an independent
Asiatic origin, was borne out by palaeontological evidence.
Since Arctotherium also occurs fossil in some Pleistocene
beds of North America it must have spread northward in
recent times and subsequently have become extinct there.

* Thering, H. von, “ Geschichte der Siidamer. Raubtiere,’’ p. 179.
Tt Osborn, H. F., “ Age of Mammals,” p. 438.
t Ameghino, F'., ‘‘'Tetraprothomo argentinus,’’ p. 230.

352 ORIGIN OF LIFE IN AMERICA

Among living bears the nearest relation of the Andean species
seems to be the Malayan bear (Ursus malayanus) inhabiting
the Malay peninsula and neighbouring countries. But the
European Miocene Ursus boeckhi and the Pliocene Ursus
etruscus are members of the same group, and it appears to me
possible that the South American Tremarctos and the Ursus
malayanus groups may have had a common ancestor which
passed from southern Europe to South America by way of the
mid-Atlantic land bridge and the Antilles in Oligocene times.

Although tapirs have a much wider range in South America
than bears, their American distribution also suggests that,
like the bears, they are immigrants either from Europe or
Asia. Their general range is in so far comparable to the
distribution just cited as the only living tapirs are confined
to South America and southern Asia. Tapirs are often alluded
to as among the most striking and familar instances of what
is called ‘‘ discontinuous distribution.’? But we know a good
deal more of the geological history of tapirs than of bears. Of
the two South American tapirs the smaller one is confined to
the Andes between Colombia and Peru, while the other
(Tapirus americanus) has probably spread eastward from a
western centre of dispersal, for it occurs from eastern Peru to
Brazil, Venezuela, Guiana and to northern Argentina. Two
other tapirs live in Central America. The genus is only known
fossil from Pleistocene South American deposits, and it might
appear as if it were a recent immigrant from North America.
But in the latter continent only a single fossil species
(Tapirus haysi) has been discovered, and that likewise in

Pleistocene beds. Professor Osborn asserts that a tapir, un- » i

distinguishable from the living South American species
(Tapirus americanus), invaded North America together with
Mylodon and Megatherium in Pleistocene times. I am not

aware of any reliable osteological characters distinguishing the © a

living South and Central American species. If there are such,
Professor Osborn’s * statement may possibly refer to one of
the latter. Still, it is quite evident that the genus Tapirus
could not have come across any Bering Strait land connection
in Pleistocene times and have travelled to Argentina before

* Osborn, H. F., “Age of Mammals,” p. 472.

es a

THE TAPIRS OF SOUTH AMERICA 353

the end of the Pleistocene Period, nor does Professor Osborn
suggest such a mode of origin. The problem, therefore, still
remains unsolved. Mr. Earle * pointed out that tapir-like
creatures or tapiroids arose about the same time in Hurope
and North America. In the light of more recent researches
it would appear that the Eocene Systemodon and Isectolophus
are confined to North America, while the European tapiroid
remains belong to the related family Lophiodontidae. The
true tapirs, to which the American genera belong, do not
make their appearance in Europe until the Oligocene Period.
According to Professor Osborn,t the existing Malayan
tapir is almost identical with the Pliocene tapir of southern
Europe (T. arvernensis), and I cannot help thinking that the
genus Tapirus has evolved in the Mediterranean region from
American ancestors much earlier than is generally supposed,
the modern tapirs having spread west and east from this centre
of dispersal at a time when the mid-Atlantic land bridge was ©
still in existence.

If we pass from Ecuador southward along the chain of the
Andes, we meet with a number of new forms of animal life,
all of which are more or less confined to this great mountain
range. In certain districts in Peru at high altitudes there
are immense colonies of curious little squirrel-like rodents
with very large ears and grey fur of extreme softness. Like
the prairie-dogs and other North American rodents, these
chinchillas, as they are called, live in burrows. There is a
larger kind, too, which has still longer ears and great black
whiskers, differing sufficiently from Chinchilla to deserve
recognition as the distinct genus Lagidium. Both genera
inhabit exclusively the high mountains between Peru and
Chile. A third member of the same tribe, the viscacha, lives on
the plains of Argentina, and will be more fully described later
on. These three genera included in the family Viscaciidae
(Lagostomidae) have, to judge from their distribution, pro-
bably originated from one or more western ancestors. But
Dr. Ameghino { has described quite a number of genera

* Karle, C., ‘‘ Fossil Mammalia of Europe,” p. 115. ~
+ Osborn, H. F., “Age of Mammals,” p. 315.
t Ameghino, FL, ‘‘ Formations sédimentaires,” p. 428.

L.A. AA

354 ORIGIN OF LIFE IN AMERICA

obviously of the same family from the Patagonian and Argen-
tine Eocene, Oligocene, Miocene and Pliocene beds, so that
it would seem, as he indeed suggests, as if South America
had been the original home of the family. Professor Schlosser
quite agrees that these are the undoubted ancestors of the still
existing South American genera, but he thinks that Dr.
Ameghino is mistaken about the age of the South American
deposits in which these rodents occur. He believes them to
be not earlier than Miocene, while more primitive ancestors
of these rodents are to be found in European Oligocene beds.
The Theridomyidae of Europe which, according to Professor
Schlosser, have given rise to Chinchilla and its relatives, are
more primitive in structure than the latter and nearly allied
to them, The same writer acknowledges that other groups of
mammals also entered South America from Europe, although
he does not give us the least clue as to the means they em-
ployed in doing so. Whether Chinchilla and its relations are
descended from European ancestors, or whether the European
Theridomyidae have been derived from South America, is
really comparatively immaterial to our present enquiries. The
important point at issue is the recognition, by such an autho-
rity as Professor Schlosser,* that the two continents have had
a faunistic interchange about Oligocene times in which North
America took no part.

Ecuador possesses such a number of quaint archaic forms
of animal life that I have scarcely been able to give a general
sketch even of the main features of the fauna, but before
dealing with the causes that produced them I must mention
one more instance. It is the most noteworthy perhaps of the
whole deer-tribe, namely, the little pudu (Pudua mephisto-
pheles). No larger than a hare, this tiny creature, with its
simple unbranched spike-antlers, reminds us of some of the

early progenitors of the deer-tribe. The genus Pudua has two

species, both entirely confined to western South America, like
the bear and Chinchilla. One of these lives in the mountains
of Ecuador, the other in Chile and on the island of Chiloé.
I need not repeat the remarks made in an earlier chapter

* Schlosser, M., ‘‘Tullberg’s System der Nagethiere,” pp. 741—
742,

ee

DWARF DEER OF SOUTH AMERICA 355

(pp. 107—112), when I argued that the South American
deer had not originated in North America, as is generally
assumed, but in South America from European ancestors.

I venture to think that most palaeontologists will agree with
my contention, which is by no means a new one, that there is
quite a remarkable affinity between the living western South
American groups of mammals and those of the early Huropean
Tertiaries. It is my interpretation of the causes which pro- -
duced this striking feature that will not so readily commend
itself. The faunas of the West Indies and Central America
form the chief difficulty to the acceptance of my theory. I
acknowledge that comparatively few traces remain in these
countries of the vast migration that swept across them. In
the West Indies, I presume, the subsequent submergence must
have destroyed the principal part of the original fauna, while
Central America in its present form did not exist at the time
when the mid-Atlantic land bridge spanned the ocean. Com-
petition with newer arrivals, moreover, must have been very
keen, so that Central America became unfitted for the survival
of Kuropean relict forms. This explanation does not appear
altogether satisfactory. But the crux of the problem is North
America. By what possible system of land bridges can
western South America have received part of its fauna from
Kurope and have exchanged certain groups in return without
North America having become affected ? This seems all the
more puzzling considering that I drew special attention in
Chapter IX. to the conspicuous faunistic relationship between
southern Europe and California. The faunas of western
North America and western South America as a whole are
strikingly different, and yet I have indicated certain points
of resemblance, especially between some of the more ancient
members of the two faunas. If we supposed the mid-
Atlantic land bridge of early Tertiary times to have been
connected at first with both western North America and
western South America, while disconnected at all other points
with these continents, certain very ancient points of resem-
blance between the two continents and with Europe might
thus receive a satisfactory explanation. If the same land
bridge had then become entirely separated from North
America, remaining united with South America, the faunistic

AA 2

356 ORIGIN OF LIFE IN AMERICA

interchange would have continued only between Europe and
South America. If the land bridge had then become discon-
nected with South America, and joined to western North
America, while the Antilles were submerged, the latest Huro-
pean emigrants would have taken refuge in California as the
last remnants of the old land sank into the Pacific. That
something of this kind actually took place I feel convinced,
although the details of these events must be founded largely
on geological studies which unfortunately are as yet insuffi-
ciently known. My own knowledge, moreover, of the geo-
logical features of the regions alluded to is only fragmentary.
Nevertheless, the little I have been able to gather does not
tend to contradict the general scheme of the theories I now
suggest.

In later Cretaceous times a broad sea, as I have pointed
out on several occasions, separated western from eastern North
America, while the Pacific Ocean flooded a large portion
of the western States, so as to leave only a comparatively
narrow strip of land between the two seas. The Cretaceous
deposits can be traced all along the Pacific coast as far almost
as the extreme tip of Lower California. Here they suddenly
stop. The Cretaceous sea evidently did not cover the in-
teresting Cape Region of Lower California nor any part of
western Mexico. There are reasons for the belief that even
at this time the western part of the coast ranges of California
were not submerged, thus suggesting the existence of another
land-mass to the west of the Californian Sea. This land may
have been connected with the Cape Region of Lower Cali-
_ fornia, and thus with Mexico. By the end of Cretaceous time,
says Professor Smith,* the subsidence and erosion of the
western part of the continent had almost established a con-
nection between the Pacific Gulfs in California and Oregon
and the old Mediterranean Sea in the Mississippi valley. The
intervening isthmus was covered by extensive marshes. Pro-
fessor Smith tells us that the geographical conditions re-
mained the same in Kocene times as in the Upper Cretaceous,
except that the sea encroached still further on the land. Now
it is precisely at this time that we notice a striking affinity

* Smith, J. Perrin, “ Geological History of California,” pp. 347—348.

SAR OOS POET | TE SEIT, | IVER ETN EE feces

ANCIENT LAND BRIDGES. 857

between the western mammalian fauna of North America and
those of Europe on the one hand and South America on the
other. Since south-western North America was then prac-
tically isolated and separated from the remainder of North
America by great ocean belts, how can we imagine these Kuro-
pean and South American affinities to have been brought
about ? Surely only by some land connection that lay to the
south. I suggest that it was from western Mexico that these
earliest mammals invaded south-western North America.
Then followed a time when the Gulf of Mexico and the Pacific
Ocean probably communicated with one another, thus separat-
ing the supposed mid-Atlantic land bridge from North
America. Professor Smith speaks only of a temporary con-
nection between the oceans, accounted for by the occurrence
in Oregon, as well as in California, of the Atlantic marine
mollusk Venericardia planicosta. Before the Miocene Period
this Atlantic connection had ceased, and the faunas of the
later Tertiary were wholly of the Pacific type, continues Pro-
fessor Smith.* He does not allude to Oligocene deposits, but
it is not long since that these were recognised at all outside
Europe. At any rate, after the Eocene follows a time during
which the Pacific recedes from the west coast, thus giving
full opportunities for an invasion of animals from the theo-
retical western land. We may suppose that this corresponded
with the Oligocene Period and with the time when, as Pro-
fessor Osborn tells us, there was a re-establishment of the
faunal resemblance of south-western North America with
Europe. Possibly Chile, which was connected at an earlier
period with this same western belt of land, became separated
from it. ‘This again was succeeded by a period of marine
transgression in the west. Hven northern Mexico was largely
covered by the sea, as well as both sides of Lower California
and a large portion of western California. All this time
western South America must have risen gradually above the
sea, and I presume that certain fragments of land, like

Peru, became joined to the long peninsula which stretched

far southward running parallel with the newly formed west
coast of South America. Thus while North America no longer

* Smith, J. Perrin, ‘‘ Geological History of California,” p. 348.

* *

858 ORIGIN OF LIFE IN AMERICA

received its quota of European emigrants, they found suitable
accommodation on the newly-formed land of north-western
South America. The mid-Atlantic land bridge now ceased
to exist, and far-reaching geographical changes super-
vened almost everywhere. Owing possibly to the extensive
subsidences in the Pacific Ocean, the land that I assume to
have occupied part of the eastern Pacific, was gradually re-
duced in size. But, being no longer tenanted by the more
vigorous and more advanced Huropean types, South American
forms now commenced to occupy this land, thus first reaching
the Antilles and then North America as it again became fully
connected with the western land. Central America in its pre-
sent shape had not yet come into existence. Not long ago it
was thought that the Central American isthmus must have
been first utilised as a highway at the beginning of the Plio-
cene Period, and that then the great edentates began to pour
into North America. Now the surprising evidence has come
to hand that true edentates of the Megalonyx type occur in the
Middle Miocene Mascall beds of Oregon. Dr. Matthew writes
to inform me that the Megalonyx remains only doubtfully
belong to this horizon. Professor Osborn,* on the other hand,
believes in the discovery, and expresses the opinion that it
tells in favour of my theory of the former existence of a
western land connecting North and South America inde-
pendently of Central America. Still, he points out that it is
inconsistent with the fact that other animals did not pass
south or north.

Let us examine some of the other new arrivals in North
America in Miocene times, and endeavour to trace their geo-
logical history. One of the most noteworthy of these is the
first appearance in North America of elephants (Mastodon).
Since Dr. Andrews’ + surprising discoveries in northern
Africa were published, Africa is generally looked upon as the
original home of elephants, the earliest form being Moeri-
therium, from which later on Palaeomastodon and its more
modern relations arose. The first of the latter was the Mas-

* Osborn, H. F., “ Age of Mammals,”’ pp. 289—292.
+ Andrews, O. W., “Tertiary Vertebrates of the Fayim,” pp. xvi—
| Xvill.

FOSSIL ELEPHANTS IN AMERICA 359

todon called Trilophodon on account of the three transverse
rows of cusps on its intermediate grinding teeth. Now Trilo-
phodon arrived in Europe and in North America at about the /
same time during the Miocene Period. Professor Osborn
assumes that these mammals came from Asia, although we
possess no evidence of their having reached the northern or —
eastern parts of that continent. We might be tempted to
invoke a direct land connection between Africa and South
America in Oligocene times, but, as we shall see later on, that
connection must have disappeared at a still earlier period.
However, these and other problems will be considered in the
next chapter.

Several important zoogeographical features of western and
northern South America still remain to be considered. Special
researches among the Cretaceous rocks and their fossils in
Peru have shown that during Lower Cretaceous time, that is to
say, towards the latter part of the Mesozoic Era, the greater
part of the country was buried deeply beneath the ocean.
From Bolivia and Chile, even as far south as the Strait of
Magellan, Lower Cretaceous deposits have been discovered.
North of Peru they occur in Colombia and Venezuela. The
most surprising circumstance connected with these South
American beds, however, is the great number of species that
are either identical with or closely allied to, such as oceur in
the Cretaceous deposits of north Africa, the south of France,
Switzerland and the neighbouring countries.* More than
sixty years ago D’Orbigny already drew attention to this fact,
and argued from it that a land connection across the mid-
Atlantic must have enabled species to cross the ocean by
travelling along a continuous shore-line. On the other hand,
scarcely any affinity exists between the Cretaceous of Vene-
zuela and that of Mexico or Texas, thus clearly implying the
presence of a land barrier between these two areas. The old
highland of Guiana east of Venezuela was long ago a penin-
sula of the archaean highlands of Brazil in the south. There
is reason to believe that the great mountain chain of the
Andes gradually emerged out of this sea. During this process
some of the newly-formed islands probably became attached

* Paulcke, W., ‘‘ Kreideformation in Siidamerika,”’ pp. 305—3808.

TTL Sh TOT FRED © PY REEMA TPA LUG ER SEL MSY EI THE OM SSD RS EE OR
|

360 ORIGIN OF LIFE IN AMERICA

to parts of pre-existing western lands. All through Tertiary
time the mountains must have continued to rise, though our
knowledge of later geological history is still meagre. -We know
that Tertiary marine deposits occur in the Orinoco valley, and
it is likely that a narrow marine channel still separated north-
western South America from the rest of the continent during
the earlier part of the Tertiary HKra. The Amazon valley no
doubt was at that time a bay of the Pacific; still, I am unaware
of any geological or zoogeographical evidence for Professor
Osborn’s supposition that north and middle South America
were completely divided in Miocene times by a wide sea. That
the Orinoco and Amazon valleys were in communication with
one another for a long time is shown by the fact that one of
the species of manatees (Trichechus inunguis) and the fresh-
water turtle Podocnemis expansa are confined to the upper
portions of these two great rivers. A most surprising
confirmation of the theory that an ocean bay extended to the
neighbourhood of the Andes has been discovered near the small
town of Pebas, on the upper Marafion, more than twenty
degrees of longitude west of the mouth of the Amazon. Pro-
fessor Boettger described deposits from this locality contain-
ing typically brackish water mollusks which could only have
lived in the neighbourhood of the sea. He naturally came to
the conclusion that the Atlantic then had invaded the Amazon
valley so as to extend near to the foot of the Andes. But
Dr. Katzer’s view, already alluded to, according to which the
Amazon drainage only changed eastward in later Tertiary
times, appears to me to agree better with the zoogeographical
features of eastern South America. Professor Boettger *
looked upon the Pebas beds as being of Oligocene, possibly
Eocene age. The fresh-water fish fauna of the Pacific slopes
of southern Keuador still exhibits such affinity to that of the
Amazon that the Ecuador mountains could only have had a
slight elevation until comparatively recent geological times.
Hence we may assume that the Pacific extended to the neigh-
bourhood of Pebas when these brackish water beds were laid
down.

An interesting zoogeographical demonstration of the

* Boettger, O., “ Die Tertiarfauna yon Pebas,”’ p..503.

Pe ST >

ot Sei ee

pod :

HISTORY OF RIVER AMAZON 861

gradual elevation and consequent slow change of the marine
character of an ancient lagoon is afforded by Lake Titicaca
on the borders of Peru. This lake, with a length of eighty
miles, lies in a mountain valley over 12,000 feet above sea-
level, and occupied not long ago a much larger area. To sup-
pose that this region should have risen from sea-level to such a
height, and still preserve the remnants of an ancient marine
fauna dating back to the period when it was a gulf of the
Pacific, would seem a very bold theory. Professor Suess,*

indeed, expresses the opinion that the presence of a marine }

fauna in Lake Titicaca cannot be regarded as a sufficient proof
of the theory that the lake was at sea-level within recent
geological times. I quite concur with Professor Suess in so
far as the assumption of a recent elevation is concerned, but
we have reason to believe that certain ancient forms of animal
life, particularly among aquatic groups, have transmitted
their specific characters unchanged to their modern descen-
dants. It is conceivable, therefore, and even possible, that the
striking affinity of the fauna of Lake Titicaca to that of the
Pacific coast may have been preserved, although the actual
junction of the lake with the sea took place perhaps as far back
as early Tertiary times. The theory of the recent elevation was
first mooted by Mr. A. Agassiz,+ owing to the discovery in the
lake of eight species of the marine amphipod Allorchestes, one
of which (A. dentatus) differs but slightly from a form still
inhabiting the Strait of Magellan. That fact alone might
be attributable to accidental dispersal, although the enormous
difference in height between the sea and the lake, and the
circumstance of there being eight different species of Allor-
chestes, would be difficult to explain on that theory. But
besides this marine crustacean other members of a marine
fauna have been shown to exist in Lake Titicaca, and thus
the case against accidental dispersal has assumed a stronger
position. The fish fauna consists of a catfish (Pigidium
rivulatum), belonging to a genus which is very widely distri-
buted all over South America, and several species of Orestias.
The latter genus is quite confined to Lake Titicaca, and since

* Suess, E., “ Antlitz der Erde,” I., p. 693.
‘t Agassiz, A., “ Lake Titicaca,” p. 287.

|

- 362 ORIGIN OF LIFE IN AMERICA

its nearest relations are all marine forms, its ancestors, as
Professor Kigenmann * remarks, could only have entered the
area when it was still a gulf of the sea.

In the Hocene Period ‘‘ Archiguiana,’’ as Dr. von Ihering
named the ancient highland of Guiana and eastern Venezuela,
was supposed by this writer to have been isolated from the
highland of Brazil. And, indeed, the mountain plateau of
Guiana contains a very large number of archaic and most
peculiar types, some of which seem to spread westward into
Venezuela and Colombia rather than into Brazil. Yet the
great majority of these ancient forms of Guiana also occur
southward in eastern Brazil. One of the most noteworthy
birds, the hoatzin (Opisthocomus hoatzin), whose young
climb about among the branches of the trees by means of
well-developed claws on their wings, and which have been
placed into a distinct order by themselves, range southward
as far as Bolivia. The chatterers (Cotingidae) comprising
some of the most ornate and peculiar birds of South America,
are almost equally divided between Brazil and Guiana. The
familiar umbrella bird (Cephalopterus ornatus), the bell bird
(Casmorhynchus niveus), the bald-headed crow (Gymnoce-
phalus calvus), and the cock-of-the-rock (Rupicola crocea), all
belong to genera which have spread westward from Guiana
rather ‘than into Brazil. In all these cases we have to deter-
mine what was the original centre of dispersal. The singular
genus of snails Ampullaria probably spread across South
America from a Brazilian centre, and so did the fresh-water
crab (Pseudothelphusa) and the whole family of fishes called
Cichlidae. The snail Strophocheilus, the fresh-water mussel
Unio, the archaic arthropod Peripatus, the family of tortoises
Cinosternidae and others, have apparently entered Brazil from
the north and west. As I shall endeavour to show in the next
chapter, many of the forms that have spread from the Brazi-
lian highlands have near relations in Africa, while among the
northern and western immigrants into Brazil scarcely any
have succeeded in crossing the Atlantic area to Africa.

* Eigenmann, OC. H., “ Freshwater Fishes of South America,” p., 521.

CHAPTER XIV

EASTERN SOUTH AMERICA

Wuen we consider that Brazil covers an area larger than
that of the whole of Europe, merely the roughest outlines of
the general zoological features of that vast country can be
attempted in a work of this nature. The highlands of Brazil,
as I have mentioned already, are confined to the east, being
surrounded by the ocean on one side and by a continuous
tract of lowlands on the others. It is believed that the
mountains were once continuous with those of Guiana
right across the present mouth of the river Amazon.
The whole of the area between the two great highlands
of Brazil and Guiana is drained by the mighty Amazon,
whose waters exceed in quantity that of any river in the world.
The Paraguay and its tributary the Parana drain the south-
western parts of Brazil. Practically the whole of the country .
lies in the tropics. The combined influence of high tempera-
ture and abundance of moisture thus produces that exuber-
ance of animal and plant life which is so characteristic of
Brazil. The great tropical forests are truly bewildering in the
wealth and variety of their vegetation, and it is here that we
realize more than anywhere else the keen struggle for exist-
ence as applied to plants and animals. In their constant efforts
to reach the light, and in their endeavour to obtain a full share
of it, the trees crowd and press upon one another until the
weaker succumb. In their turn they are invaded again by
others, while hosts of enemies, parasitic plants and climbers,
twine round and strangle the less sturdy long before they
succeed in attaining their object. Weare thus presented with
a scene of savage warfare among plants. It is less evident
among animals. But the ringing sound of the multitude of
voices issuing out of the forest reminds the traveller that in
this teeming profusion of nature there must be an acute

364 ORIGIN OF LIFE IN AMERICA

struggle for life among animals as well as among plants.
And yet, except birds, insects and lizards, animals do
not appear to be present in unusually large numbers. The
large class of mammals, which elsewhere form such a con-
spicuous feature of a fauna, seem almost to be absent. This
is largely due to the fact that Brazil is really poor in terrestrial
mammals. Those that do inhabit the country are chiefly of
arboreal habits, and thus escape attention. Mr. Bates *
believes that the South American fauna has been slowly
adapted to an arboreal life, and that extensive forests
must always have existed since the region was first peopled
by mammalia.

Among these arboreal mammals the family of the capuchin

monkeys (Cebidae), whose unusually prehensile tail gives
them peculiar facilities for climbing, are the most noteworthy.
They range all over tropical America, being most abundant
in the dense forest regions of Brazil. In some monkeys, like
the howlers (Mycetes), the end of the tail underneath is devoid
of hair, and thus acts with even greater efficiency than in
capuchins (Cebus). The sakis (Pithecia) and squirrel-mon-
keys (Chrysothrix) have non-prehensile tails. The spider
monkeys, with their long limbs and long prehensile tail, are
the most admirably adapted creatures for a purely arboreal
life. A second family (Hapalidae) includes the smallest of all
monkeys, the marmosets. Mostly very active little squirrel-
like creatures, with arboreal habits, they are almost confined
to Brazil and north-western South America. In many respects
these two families of South American monkeys are closely
related to one another, whereas they differ from the Old World
species, especially in their dentition. Since no members of
the Cebidae and Hapalidae have ever been found fossil outside
South or Central America, it is believed that they form a
branch distinct from the Old World monkeys, having had a
separate origin from lemur-like creatures. Dr. Ameghino has
described quite a number of lemuroid remains from the Cre-
taceous of Patagonia, and he maintains that these early fore-
runners of monkeys and man originated in the ancient vast
territories of southern South America. I am fully aware that

* Bates, H. W., “ Naturalist on the Amazons,”’ p. 32.

——e "> 2 ee -

THE MONKEYS OF SOUTH AMERICA 365

the views of Dr. Ameghino * as to the age of these beds have
received a considerable amount of adverse criticism. Still,
if we assume the correctness of his arguments and the former
existence of a land bridge between South America and Africa,
these lemuroid mammals might have passed from Patagonia,
as Dr. Ameghino supposes, to Africa and thence to Kurope,
and lastly, from there to North America. I do not think that
this was the history of events. One distinct branch may
have travelled from Patagonia to Chile, and thence direct to
North America by a western land connection (compare
Fig. 14), which I have already mentioned and which will be
further discussed in the next chapter. From North America it
may have passed into Europe by the mid-Atlantic land bridge.
I doubt whether a’separate branch reached Africa from South
America by a land bridge, which Dr. Ameghino contends
joined these two continents. However, it is this very problem
of the zoological affinity between South America and Africa
and its origin which will be dealt with in this chapter.

What we have to consider principally, therefore, is
whether there are really such affinities between the living
faunas of the two continents as to make it probable that
the latter were once connected with one another by land.
The capuchin and marmoset families, which are quite con-
fined to South and Central America, have probably originated
there in the remote past and have not been able to pass into
any other continent. All we know of their immediate ancestry
is that in the Hocene deposits of Patagonia a new family
of monkey-like creatures arose, possessing certain marks of
resemblance to the two recent South American families. They
were named “ Homunculidae ” by Dr. Ameghino. As these
also are quite unknown outside South America, it would
appear as if Patagonia had become isolated during the course
of the Eocene Period from the rest of the world. We cer-
tainly have no evidence of any Tertiary land connection
between the southern portions of South America and Africa
from the distribution of monkeys.

Another typically Brazilian arboreal mammal is the sloth,
which lazily and cautiously moves from branch to branch

* Ameghino, F'l., “ Formations sédimentaires de Patagonie,”’ p. 289.

366 ORIGIN OF LIFE IN AMERICA

supported by the long claws of its toes. Two genera of this
edentate mammal are known, viz., Bradypus and Choloepus,
both of them confined to South and Central America; and, like
the monkeys, absent from Argentina, Chile and Patagonia.
In spite of their absence from the latter country, it is there,
according to Dr. Ameghino, that we find the earliest traces
of the sloth-tribe in the Eocene beds. The Eocene Entelops
and Trematherium have been placed into the same family
with the modern sloths. Certain sloth-like remains have even
been traced back to the Upper Cretaceous of Patagonia.
Sloths of the arboreal type have not been found fossil out-
side South America. The remains of a supposed sloth (Brady-
therium) were discovered by Mr. Grandidier ten years ago
on the island of Madagascar. According to Dr. Smith Wood-
ward they belong to a lemur, yet there are so many other
points of affinity between South America and Madagascar
that a former direct land connection between the two regions
has been suggested: I return to this subject more fully in
the next chapter.

In a previous chapter (p. 70) I explained that, although
all American porcupines are arboreal in distinction to the
Old World species which live on the ground, only the
South and Central American forms have prehensile tails.
This gives them greater facilities for dispersal in Brazil, and
greater protection from their enemies. These South
American porcupines agree in their general range with the
monkeys and the sloths, and like them are absent from the
southern states of South America, although their ancestral
home was seemingly in Patagonia. Some species of Coéndu
are known from the Brazilian caves, still, the centre of origin
lay manifestly further south.

Of the pouched or marsupial mammals we have noticed that
the opossum has a wide range in North America. In Central
and South America the same North American species
(Didelphys marsupialis) occurs widely distributed. Such an
enormously extensive range must be due to the fact of its
being a persistent mammalian type. The genus, or one
closely related to it, certainly was already represented in the
Lower Eocene of North America and the Upper Eocene of
France. Only one genus of these marsupial mammals occurs

ae a ee ee

SOUTH AMERICAN SLOTHS 367

in North America. From South America three others are
known. The general range of the family Didelphyidae points
to South America as the centre of dispersal. Although the
genus Didelphys or Peratherium has been met with in the
Eocene of North America and France, while it first appears
in South America in the Miocene Period, if Dr. Ameghino is
correct, the earliest member of the family (Proteodidelphys)
occurs in the Lower Cretaceous beds of Patagonia. Even if
we look upon these beds, with Professor Osborn, as really of
Eocene age, the more primitive characters of Proteodidelphys
point to South America as the ancestral home of the family,
and on this continent no doubt the genus Didelphys has
originated and not in south-eastern Asia, as suggested
by Mr. Lydekker.* I think the geological history of the
opossums, though dating further back than that of the South
American monkeys, followed much upon the lines of the
groups just considered, at any rate, they seem to have entered
Brazil about the same time.

Among the birds of South America we have precisely
similar examples, except that in their case we know unfor-
tunately very little of their past history from palaeontological
evidence. The wonderful family of humming birds (Trochi-
lidae) is comparable in distribution with the opossums, in so
far as it ranges all over South and Central America. It
has in all likelihood entered North America in later geological
times. Not a single species of humming bird is known be-
yond the confines of America. It is of importance to note that
of the one hundred and eighteen genera admitted by Dr. Har-
tert,~ the great majority are confined to the west coast. Some
of them inhabit Chile, others Peru, Bolivia, Ecuador,
Colombia, Central America and Mexico. A few (Oreotro-
chilus) live at enormous heights, up to 20,000 feet. Others
are limited in their range to the Antilles and Brazil. Only
the single genus Avocettula, with one species, is peculiar to
Guiana. This seems to suggest that the family originated in
western South America, and has only gradually spread east-
ward on the mainland. The West Indian area no doubt was

* Lydekker, R., ‘‘ Geographical History of Mammals,” p. 112.
+ Hartert, E., “'Trochilidae,’’

368 ORIGIN OF LIFE IN AMERICA

invaded by the humming birds in earlier times from the west,
since several very distinct genera with well marked characters
have originated there. The humming birds constitute a
sharply defined family, whose nearest relatives are the tree-
swifts (Macropteryx) of southern Asia and western Polynesia.
The common ancestors of these two groups may possibly
have inhabited part of the supposed ancient Pacific continent,
and may have diverged from it east and westward when it sub-
sided. As Dr. Wallace* aptly remarks, no naturalist can
study in detail this single family of birds without being pro-
foundly impressed by the vast antiquity of the South
American continent, its long isolation from the rest of the
land surface of the globe, and the persistence through count-
less ages of all the conditions requisite for the development
and increase of varied forms of animal life.

The chatterers(Cotingidae) which have already been alluded
to as comprising some of the most beautiful and noteworthy
of American birds, are almost confined to South and Central
America and the West Indies. Only a few species enter North
America in Mexico. The curious toucans (Rhamphastidae)
with their huge bills and strange texture and coloration of
their plumage, as well as several other families, are restricted
to South and Central America and have no near relations in
the Old World.

If South America had been connected by land with Africa
in later Tertiary times, we should expect, at any rate, such
mobile creatures as birds and also butterflies to indicate by
their distribution the former existence of such a land bridge.
Among the most conspicuous butterflies in the Brazilian
forests, Mr. Bates mentions the Heliconiidae, which are
readily recognisable by their long narrow black wings,
variously ornamented with white, crimson and yellow dots
or stripes. Yet the family is almost purely South American.
A single species only (Heliconius charitonia) passes into
Mexico.t ae | |
_ The Morphidae likewise range from Argentina to Mexico,

some of the larger species, with their dazzling metallic

* Wallace, A. R., “ Distribution of Animals,” IL., p. 9.
+ Stichel, H., and H. Riffarth, “ Heliconiidae,”

ae ae oe ee

BIRDS OF SOUTH AMERICA 369

colours, being characteristic of the Brazilian forest fauna.

The family is unknown in the Old World, but, as in the case
of the humming birds, we have closely allied groups (Ama-
thusidae, etc.) in western Polynesia and southern Asia, so
that the Morphidae or their ancestors may possibly have
entered South America, as so many other groups have done,
from the west.

The large and mostly active lizards belonging to the family
Teiidae are spread all over South America, ranging northward
as far as California and Texas and through the West Indies.
They appear to have only extended their range into North
America in comparatively late geological times, although they
are known from early Tertiary deposits in South America.
Nevertheless the Teiidae are quite unknown in the Old World.
Instances of that kind might easily be cited from every group
of vertebrates and invertebrates.

Yet although these examples seem to show that the faunistic
community between South America and Africa is so slight
as not to necessitate the hypothesis of a former land connec-
tion between these continents, we possess other very striking
features of distribution which are strongly opposed to such
a conclusion. I may draw attention again to the most re-
markable fact, pointed out by Professor Bouvier,* that the
genus Peripatus is peculiar to America, with the single ex-
ception of Peripatus tholloni of West Africa. All the other
Peripatus-like creatures have been proved by Professor
Bouvier to belong to different genera or groups.

During his travels in the Amazon region, Mr. Bates dis-
covered a curious archaic spider-like creature, which was
named Cryptostemma westermanni. More recently the same
species has been recorded from Sierra Leone and from the
Cameroons in West Africa. Those who allege that accidental
dispersal is responsible for such cases of distribution, pro-
bably accept the discovery of Cryptostemma westermanni
on both sides of the Atlantic as a notable instance of the
facility with which species are wafted across the ocean. But
we must remember that there are thousands of species of
animals and plants inhabiting the coasts of West Africa and

* Bouvier, E. L., ‘‘ Monographie des Onychophores,” I., p. 91.
L.A. BB

870 ORIGIN OF LIFE -IN AMERICA

Brazil that are specifically and generically distinct from one
another, although more fitted for accidental dispersal across
the ocean than Cryptostemma is. The instances of such
specific or generic identity of animals and plants, in fact, are
scarce. Moreover, Cryptostemma is the single survivor that
has yet been brought to light of the otherwise extinct order
Meridogastra, which occupies a somewhat intermediate posi-
tion between the true spiders and what are called “ harvest-
men.’’* For this reason it must, like Peripatus, be looked
upon as an exceedingly ancient relict member of our fauna.

Let us take another group of apparently very ancient
animals, the worm-like and limbless coecilians, which live
underground. Dr. Boulengery tells us that of the genus
Dermophis three species are found in Central and South
America, one in West Africa and another in East Africa, and
that the genus Herpele is confined to Gaboon in West Africa
and Panama. Dr. Sarasin argues that the dispersal of
Herpele at any rate dates from pre-Cretaceous times. It
seems possible, therefore, that these few archaic creatures
indicating faunistic relationship between South America and
Africa, have obtained their present range during some very
remote geological period, when the conditions of land and
water were entirely different from what they are at present,
and that they are not to be regarded as instances of accidental
dispersal across the Atlantic. The suggestion that South
America and Africa were once united by land is not a new one.
It has been made, as we have learnt, by various authorities on
entirely different grounds. Considering the contradictory
nature of the evidence, however, the problem requires close
scrutiny.

I have already stated that Dr. Ameghino had expressed the
opinion, based on the evidence of the fossil mammals, that
South America and Africa were joined by a land bridge during
the whole of Upper Cretaceous times. During the Eocene
Period this land connection, he thinks, became more restricted
or narrowed down, while it still persisted incompletely as a
chain of islands, until middle Miocene times. Dr. Ame-

* Karsch, F., “ Uber Cryptostemma,” pp. 25—29.
+ Boulenger, G. A., “Synopsis of apodal Batrachians,” pp. 404—409.

FOSSIL MAMMALS - 371

ghino’s * arguments in favour of this union of South America
and Africa are not founded on any palaeontological resem-
blance between these two continents, but rather on the affinity
of the fossil mammals of South America to those of Europe,
Asia and North America. Since I have shown that until
about Oligocene times southern Europe was connected by
land with western South America, by way of the West Indies
and part of Central America, there does not seem to be any
necessity for a second land bridge further south in order to
account for the mammalian affinities existing between South
America.and Europe as well as Asia and North America.
Professor Osborn does not recognise the existence of any
former land bridge during the age of mammals between South
America and the Old World except by way of North America.

Mr. Lydekker t argues that the only marked community
between the Ethiopian and Neogaeic(South American) faunas
as regards mammals, relates to the hystricomorphous rodents,
but he thinks this community is a very marked one and diffi-
cult to explain on any other hypothesis than that of a land
connection between the two areas. The Hystricomorpha are
a section of the rodent mammals, well distinguished by mor-
phological characters from the other sections of that order.
It is of the greatest importance to note that this hystrico-
morphous section is now confined to Africa and America,
with the exception of a couple of genera which range into
southern HKurope and Asia. The centre of distribution is
no doubt South America. If they had passed from there to
Africa, we should expect them to be found in Brazil and
western Africa. Let us examine the two closely related
families of Octodontidae and Ctenodactylidae, which are in-
cluded in the section Hystricomorpha. The first is con-
fined to South America, the other to Africa. Of the former
it is the sub-family Octodontinae which is nearest related
to the Ctenodactylidae, and almost entirely confined to
Argentina and the west coast of South America. Only a few
species like Ctenomys brasiliensis and Ct. minutus really
enter Brazil. The extinct species are all but one confined to

* Ameghino, F., ‘‘ Formations sédimentaires,”’ pp. 281—287.
t+ Lydekker, R., “ History of Mammals,” p. 127.

BB2

372 ORIGIN OF LIFE IN AMERICA

Argentina. It seems manifest, therefore, that the ancestral
members of this sub-family have travelled along -the west
coast of South America probably from a southern centre of
dispersal. We find no trace of them in Central America or the
Antilles, but it is in North Africa where we meet with
Ctenodactylus with its peculiarly modified inner toes. Here
in the Mediterranean region, and not in Africa proper, must
have been the Old World centre of dispersal, for we find the
allied extinct genus Pellegrinia in the Pleistocene of Sicily,
and Ruscinomys in the Pliocene of southern France. A
recent relation of Ctenodactylus. (Massoutiera) has passed
southward towards the Senegal. The main branch, however,
has apparently invaded eastern Africa from the Mediterranean
region, giving rise to the genera Pectinator, Thryonomys and
Petromys. Only a single species (Thryonomys swinderianus)
has gained the west coast of Africa. Of the sub-family
Echimyinae, which largely inhabits Brazil, Africa possesses
no near relations. The only African family of the hystrico-
morphous rodents, that of the Cape jumping hares (Pede-
tidae), occupies a more isolated position, its exact relationship
being still somewhat obscure. But in any case, I fail to
deduce sufficient evidence from the distribution of these
hystricomorphous rodents, in favour of a direct land connec-
tion between South America and Africa, although there must
have been one between the Mediterranean region and western
South America. by way of the West Indies and Central
America (see p. 280 and Fig. 14).

Apart from the cape jumping hares (Pededitae), there are
in South Africa certain mammals which indicate a distant
relationship with South American ones. The peculiar pig-
like African edentate Orycteropus occurs in Africa, while
another edentate, the pangolin (Manis), inhabits Africa and
the Indian region. Dr. Tullberg thought that these and other
features implied that south-western Africa must have been
joined by land to South America during a time when the
former was completely severed from the rest of Africa. But
even this land bridge ceased to exist, according to Professor
Tullberg,* at the beginning of the Tertiary Era, at latest in

* Tullberg, T., “ System der Nagetiere,”’ p. 498.

ae Sh te Ss

OLD WORLD AFFINITIES 878

Eocene times. He thought that south-western Africa later on
became united with eastern Africa, thus enabling some of
these ancient mammals of South American origin to spread
northward towards Europe and eastward into Asia. But both
the Manidae and the Orycteropidae are represented in the
_ Eocene deposits of southern Europe, while the genus Orycte-
ropus lived in Samos and on the mainland of Greece 1 in Miocene
times. Moreover, neither Manis nor Orycteropus are confined
to southern Africa. Both are distributed north-eastward as
far as Kordofan and Senaar. It seems more likely, therefore,
that these edentates, like the hystricomorphous rodents just
alluded to, have originated in the Mediterranean region from
- South American ancestors and have spread southward subse-
quently.

The same problem has also been discussed by Dr. Andrews*
as the result of his remarkable discoveries of fossil mammals
in the Fayam of Egypt. All the Carnivora he found there
belonged to that archaic group known as the ‘“ Creodonta.”’
He argues that the presence of these creodonts in Africa would
account for the existence of the ‘“ Sparassodonta ” in Pata.
gonia, if we assumed that during the remote period when these
ancient groups originated, Africa and South America had
been joined to one another by land. He also brings forward
another testimony in support of his suggestion, which I shall
deal with later on. As for the Creodonta, they are so amply
represented in the early Tertiaries of both North America and

Europe, that the assumption of a mid-Atlantic land bridge is _

sufficient to explain their presence in these continents as well
as in Kgypt, while Patagonia must have had some land con-
nection with North America in late Cretaceous or early
HKocene times.

The distribution of birds does not give us many definite
suggestions as to former land connections between South
America and Africa. The range of the parrots (Psittacidae),
however, points to an affinity between these continents. A
more striking example seems to be that of the ostrich and
rhea. The former inhabits exclusively Africa and Arabia, the
other Argentina and Brazil. Hence we might be tempted to

* Andrews, C. W., ‘‘ Tertiary Vertebrates of the Fayim,” p. xxii.

374 ORIGIN OF LIFE IN AMERICA

explain their present range by a direct land bridge between
the two continents. The American ostrich (Rhea) is only
known fossil from superficial deposits, but the ostrich (Stru-
thio) occurs in the Miocene or Lower Pliocene of the Siwaliks
of India and of the island of Samos. Since the ostrich once
| lived in the Mediterranean region, it is possible that the
common ancestor of the two families may have utilised the
mid-Atlantic land bridge to travel from the Old World to
the New or vice versa.

The reptiles and amphibians, as Dr. Blanford * has pointed
out, indicate a much more pronounced faunal relationship
between South America and Africa than the birds or mammals
do. Professor Pfeffer + endeavoured to explain this very inge-
niously by the assumption of a former sub-universal, or
almost universal, distribution and a subsequent extinction on
the northern continents. He admits that some form of
land bridge was necessary, of course, yet almost all inter-
continental communication must have passed, according
to his views, across a Bering Strait land bridge. He
quotes a number of instances of groups which are now
confined to the southern hemisphere, but have once also
extended to the northern continents, and because they
have done so he contends that they must have had a
sub-universal distribution. All those examples which are
not found fossil in the northern hemisphere are nevertheless
supposed to have had a similar range and to have gained their
present southern distribution in different countries by wander-
ing from one to the other almost by way of the North Pole and
then south again. Nothing but a careful general study of
existing distribution can convince us of the fallacy of such
an assumption.

Let us take, for instance, the family of fresh-water tortoises,
the Pelomedusidae. It is confined to Africa, including Mada-
gascar, and South America. Curiously enough, one of the
genera of this family, viz., Podocnemis at present inhabits
only northern South America and Madagascar. But, as Pro-
fessor Pfeffer tells us, the genus is known as far back as

* Blanford, W. T., ‘“‘ Anniversary Address,” pp. 70—-71.
+ Pfeffer, G., “ Zoogeographische Beziehungen,” pp. 417—418,

gin iat a ee

—

> ee oe Ce, ~ Ee > eee ee

SOUTH ATLANTIC LAND BRIDGE 875

the Cretaceous of Patagonia and New Zealand, the Eocene
of Egypt, England and India, and the Miocene of Egypt and
Malta. The faunistic relationship between Patagonia and New
Zealand will be explained later on, yet it has by no means been
produced. by a sub-universal distribution. The only fossil oc-
currence of. Podocnemis we know of from Africa is that from
Egypt, and even that, with Malta and England, is rather sug-
gestive of a radiation from a Mediterranean centre. The
dispersal from an originally Patagonian birthplace may have
taken place westward to New Zealand and northward along
the ancient land connection, which I described as extending
by way of Central America to southern Europe. It is impor-
tant to bear in mind this very peculiar case of faunistic rela-
tionship between South America and Madagascar, exclusive
of the African continent, because similar instances are met
with among many groups of animals and plants. I have
already alluded to one, and it was first suggested by Dr.
H. O. Forbes, I think, that this range was due to a former '
direct land connection between Patagonia and Madagascar.
I drew attention in a former chapter (p. 173) to the
members of the family Amphisbaenidae as furnishing, on
account of their subterranean habits, important evidences
of former changes of land and water. I may men-
tion again that they are limbless, wormlike liazrds, and
that many of them live underground in ants’ nests. They
are not liable, therefore, to accidental dispersal. Their
distribution is most interesting. They inhabit mostly Africa
and South America. A few occur in the West Indies and
the Mediterranean region. Some have even spread into the
southern States of North America, and we possess a few
‘remains from Oligocene deposits. Otherwise we know nothing
of their past history. We might suppose that some early mem-
ber of this family had spread across the mid-Atlantic land
bridge to the Mediterranean region and thence colonised
Africa with Amphisbaenidae. But in this instance such a
land bridge cannot help us, because the genus Amphisbaena
occurs in Africa and South America, while the Mediterranean
region is inhabited by the genus Blanus. The latter, no doubt,
may owe its origin to a migration across this mid-Atlantic
land bridge, still we can scarcely imagine that, coming from

376 ORIGIN OF LIFE IN AMERICA

the north, and after having given rise to Blanus in southern
Europe, the American ancestor reverted again to Amphisbaena
when it reached Africa. Amphisbaena, moreover, is represented
in Brazil by about a dozen species, some of which are very
closely allied to those of Sierra Leone and Liberia in West
Africa. If we attribute such a range to a former sub-universal
distribution, as Professor Pfeffer suggests, then practically
all animals with a wide southern range must at some time or
other have passed through North America and Asia or Hurope
to raach their present habitats, and for such an assumption
we have no palaeontological evidence. I think a case of this
kind, as Dr. Blanford remarks, implies a former land con-
nection between South America and Africa. We possess
among the Amphisbaenidae an even more striking example of
faunal relationship between these two continents. There are
two species of Anops, one of which (Anops kingi) ranges
from Brazil to Argentina, while the only other species (A.
africanus) is confined to West Africa.

Of particular interest are the skinks (Scincidae), as I
explained (p. 124) that this family must be of very great
antiquity. Some of the genera certainly date back to Meso-
zoic times. Now, while skinks are abundant in North
America, the southern continent is almost entirely free
from these lizards. Those that live there, at any rate,
belong to a genus distinct from the northern one. Southern
Asia and Africa are the headquarters of this large family.
Only the single genus Mabuia has spread into South
America. Mabuia occurs principally in southern Asia,
Madagascar and Africa. A few species are known from
the Cape Verde islands. on the west coast of Africa,
while one (Mabuia punctata), very closely allied to them,
has been met with on the island of Fernando de Noronha
off the east coast of South America and also in (7ulana.
Three species are found in Brazil. A couple have passed
northward penetrating into Central America and one even
to the Greater Antilles. We have clear evidence here of
a former land connection between West Africa and South
America and of its having been utilised by the skink, Mabuia,
in traversing the Atlantic in a westward direction.

Tbe worm-like amphibian Dermophis has not yet been

LIZARDS, FROGS AND TOADS _877

noticed in eastern South America, but to judge from the cir-
cumstance that one species lives in east Africa, another in west
Africa, a third in Ecuador, and a fourth in Central America,
according to Dr. Boulenger,* we may conclude that the genus
will probably turn up in Guiana.

The frogs and toads are divided into two groups, one of which
(a very small one) contains those that are devoid of a tongue,
while all others possess this useful organ. The tongueless
toads are generally looked upon as the most primitive of the
_ tailless amphibians. Three genera of these creatures are
known to-science, two (Xenopus and Hymenochirus) inhabit-
ing Africa south of the Sahara, the other (Pipa) castern
South America. The only member of the last genus is the
remarkable Surinam toad (Pipa americana) whose skin on
the back of the female is provided with pits in which the
eggs are placed and the young undergo their whole metamor-
phosis. These tongueless toads (Aglossa) are not known
as fossils. We have thus to conjecture the origin of their dis-
persal from their present distribution which is highly sug-
gestive of a former direct land bridge between Africa and
South America. This view is considerably strengthened by
the fact that the West African Hymenochirus is in several
respects more closely related to Pipa than to Xenopus.

~The toothless frogs (Dendrobatidae) appear at first sight
to be typical examples of a group which has obtained its pre-
sent range by means of a former land bridge between South
America and Africa. They occur only in northern South
America, in west Africa and Madagascar, a discontinuous dis-
tribution which betokens antiquity, and which is not unknown
among other animals and plants. Yet Dr. Gadowy argues
that the Old World and New World genera were evolved inde-
pendently from toothed frogs, that this is, in fact, a case of
convergence. It may be so, but his arguments are by no
means convincing.

I may once more be permitted to draw attention here to
the opinion long ago expressed by Dr. Gill ¢ that fishes are

* Boulenger, G. A., “Synopsis of apodal Batrachians,”’ p. 404.
t+ Gadow, H., “ Amphibia and Reptiles,’ p. 272.
{ Gill, T., “ Principles of Zoogeography,”’ pp. 29—30.

378 ORIGIN OF LIFE IN AMERICA

among the best indicators of past continental changes,
and that the relations of the several southern continents as
to their ichthyic faunas can be best understood by the assump-
tion that, at some remote epoch or epochs, there was distribu-
tion of land and water which eventually permitted an emigra-
tion and immigration of types from one into another. Dr.
Ginther * enunciated similar views. He thought that the
existence of so many similar forms of fishes on both sides of
the southern Atlantic supported the supposition that they are
the descendants of a common stock which had its home in a
region now submerged under some intervening part of the
ocean. Since the days when these two great authorities pro-
nounced upon this subject, the ichthyology of both Africa and
South America has become better known, and new light has
been thrown on the relationship between the various groups
of fishes. We can deal with the problem now in the light of
the latest researches. Dr. Boulenger has made a special study
of the African fish fauna, while Mr. Regan and Professor
Kigenmann have paid particular attention to the ichthyology
of South America. In his interesting address to the British
Association on the distribution of African fishes Dr. Bou-
lenger mentions Protopterus as the most noteworthy fish of
Africa. In some respects it approaches the amphibia. It
possesses a double lung as well as gills, and is able to live for
a long period in dried mud. ‘Anatomically there are many
characters in which it differs from almost all other fishes.
Its only living relation, Lepidosiren of Brazil, is very similar
‘in form and so closely allied that the two are placed into
the same family Lepidosirenidae. Professor Pfeffer + con-
tends that since this family is represented in the Permian
and Trias of western North America, in the Trias of India
and South Africa, in the Cretaceous of Patagonia and the
Trias and Jurassic of Europe it must have had a universal dis-
tribution. Hence he argues that the occurrence of Pro-
topterus in Africa and of Lepidosiren in South America can
have no significance in supporting the theory of a former
land connection between these two continents. But recent

* Giinther, Albert, “Study of Fishes,” p. 233.
+ Pfeffer, G., “‘ Zoogeographische Beziehungen,”’ p. 483,

er

—_ RoR Da a

THE FISHES OF SOUTH AMERICA 379

researches have shown that these extinct forms all belong
to the genus Ceratodus, that all are members of the family
Ceratodidae.* The only fossil member of the Lepidosirenidae
is Protopterus libycus of Egypt. There is really no reason,
therefore, as Dr. Boulenger y+ puts it, why the latter family
should not have passed from one of the two continents into the
other when they were connected by land.

Another striking feature of the South American fresh-water
fish fauna is the extraordinary number and variety of forms
of the Characinidae, unquestionably, according to Dr. Bou-
_lenger, one of the most lowly and generalised groups of ex-
clusively fresh-water teleosts. They are likewise abundantly
represented in western and central Africa, yet not a single
genus is common to both continents. Hence Dr. Boulenger ft
concludes that it is quite legitimate to explain the distribu-
tion of this family by the assumption of a land bridge con-
necting Africa and South America about the end of the
Cretaceous Period. |

A similar argument is used by Mr. Regan § to account for
the large fresh-water family Cichlidae (compare Fig. 12) in
these two continents, except that he is of opinion that the
land bridge was still in existence in early Kocene times.

Professor Eigenmann || states that there is no known means
by which these two families could have crossed the existing
gap between Africa and South America. There has been no
exchange of species in recent times, for there is no species
or genus common to the two continents. The South American
and African elements of these two families must have been
derived from some intermediate land-mass, or must have
travelled from one continent to the other over a land bridge.
That this connection must have been obliterated before the
Tertiary Era is evidenced, he remarks, by the fact that the
Tertiary deposits of Taubaté and Parana include existing
genera, and that many South American families of fishes

* Goodrich, E. 8., “ Cyclostomes and Fishes,” p. 258.

+ Boulenger, G. A., “ Distribution of African Fishes,” p. 5.

{ Boulenger, G. A., “ Distribution of African Fishes,” p. 6. —

§ Regan, T., “ Fishes of Central America,” p. xiv.

|| Higenmann, C., “ Fishes of South and Middle America,” pp. 525—
526,

380 ORIGIN OF LIFE IN AMERICA

which are absent from Africa have arisen in South America
from the Characinidae and Siluridae since the separation of
the two continents.

Dr. von Ihering’s early recognition of the importance of
fresh-water faunas as an aid to the palaeogeographical studies
of the Palaeozoic and Mesozoic Eras, has led to very remark-
able results. Some of these I have indicated already. His
noteworthy discovery that some of the fresh-water bivalves
of South America have a “‘lasidium’”’ larva, while all the
Unionidae possess a “‘glochidium,’’ placed the family Mute-
lidae into quite a different position. The Mutelidae are a
family essentially South American and African, demonstrat-
' ing clearly, as Dr. von Ihering * admits, the existence of a
— land connection between South America and Africa during the
Mesozoic Era.

The family Achatinidae includes some of the largest and
most conspicuous land-snails, Achatina achatina growing to a
length of seven inches. Their distribution, which is well
known, indicates an African centre of evolution. The early
members of the family are unknown and should be looked for
in mid-Mesozoic deposits, according to Dr. Pilsbry.t The
same authority believes that some of the sections of the Acha-
tinidae migrated to South America before the interruption of
the land connection across the tropical Atlantic. Dr. Pilsbry,
who in his earlier volumes condemns the practice of throwing
hypothetical bridges across the oceans, now almost takes it as
a matter of course that Africa and South America were once
* united by land. The mollusks, as most other groups of
animals, yield facts of distribution that are quite unexplain-
» able by the theory of accidental dispersal, and many of those
who at first were firm believers in the immutability of our
ocean basins, have entirely changed their opinions after a
careful study of zoogeography. It is the smaller kinds of the
Achatinidae which show the affinity between the two con-
tinents most clearly. Thus the genus Subulina is confined to
Africa and tropical America while Opeas and Pseudopus have
spread to other parts as well.

* Therine, H. von, “ Archhelenis and Archinotis,”’ pp. 125—145.
+ Pilsbry, H. A., ‘“ Manual of Conchology,” Vol. XVIIL, p. vi.

FAUNISTIC PROBLEMS 381

It is now fifty years since Mr. Andrew Murray * first
directed attention to the fact that the beetle Tauna® of Old
Calabar in West Africa presented certain affinities with that
of South America. He even then suggested that some sort of
communication must once have existed between these two
regions of the earth. A few years later he returned to the
same problem, éxpressing the opinion that this communica-
tion consisted of an actual land bridge of which the only re-
maining vestiges are the islands of Ascension, St. Paul’s, St. |
Helena and Tristan da Cunha.+

Great stress is also laid on this remarkable relationship
between the southern continents by Professor Kolbe,t but he
explains it by the assumption of a land bridge far to the
south of the Equator.

Dr. Packard § was good enough to inform me some years
ago that the distribution of the Lepidoptera was distinctly
in favour of the theory of a former union between South
America and Africa. He alluded in particular to a family of
moths known as the Saturnidae, stating that their general
range confirmed the view arrived at from other sources, that
perhaps at the close of the Cretaceous Period and through
the early part of the Tertiary Era the two continents were
connected with one another by land.

The importance of the fresh-water crabs in the solution of
problems of this nature has been emphasised, as I mentioned
before, by Dr. Ortmann,|| who showed that the west African
Potamoninae are geographically most closely approached by
the South American Potamocarcininae, and that this suggested
a former union of these regions. This land bridge in its full
extent, he thinks, existed during the Jurassic and in early
Cretaceous time. In the middle of the Cretaceous Period the
southern Atlantic advanced northward and gradually invaded
the east coast of South America extending as far as the
Amazon valley. Guiana still remained joined to West Africa
during the remainder of the Cretaceous Period, and was not

* Murray, A., “ Coleoptera of Old Calabar,” pp. 453—454.

+ Murray, A., “ Coleopterous Faunae,” p. 15.

t Kolbe, H. J., “ Die Coprophagen Lamellicornier,”’ p. 503.

§ Packard, A. S., “ Larval Forms of Moths,”’ p. 280.

|| Ortmann, A. E., “ Distribution of Decapods,” pp. 350—351.

382 ORIGIN OF LIFE IN AMERICA

finally destroyed until early Tertiary times (compare Figs. 15
and 20). Quite recently, however, Dr. Ortmann * argued that
this ‘“ Archhelenis” of Dr. von Ihering must have sunk
beneath the waves of the ocean by the end of the Mesozoic Era.

Some time ago Mr. Pocock + pointed out that the scorpions
of the genus Opisthacanthus were confined to tropical Africa,
Madagascar and South America. Our knowledge of the dis-
tribution of scorpions has increased considerably since he
wrote his essay, but the range of Opisthacanthus has not been
greatly extended. It occurs in west, east and south Africa
and Madagascar, while it reappears on the opposite side of the
Atlantic in Colombia and the island of Haiti. It is not known
from either Brazil or Guiana and may possibly have become
extinct there. On the other hand, Damon, one of the ‘Tarantu-
lidae, occurs in west and east Africa and from Brazil to Pata-
gonia. Professor Kraepelin { assumes that because the African
Damon variegatus in a specifically identical form actually
inhabits South America, it must have been introduced into the
latter continent, yet in another place he urges that several
of the centipedes (Scolopendridae) probably maintained their
specific characters from archaic times to the present day. Like
some of the species of Otocryptops, Rhysida and Scolopendra
and the curious arachnid Cryptostemma, Damon variegatus
may possibly represent one of these ancient species which
has retained its morphological characters unchanged since
Mesozoic times. |

The numerous examples, cited above, indicate that there
exists a perfectly recognisable faunistic relationship between
tropical Africa and tropical South America. Nevertheless this
relationship rarely extends to genera and species. If so it is
confined to forms like Anops, Mabuia, Subulina, Opistha-
canthus, Cryptostemma and others, of which there is reason
to believe that they are extremely ancient types. From some
cause or other they may have retained their specific or generic
characters throughout a series of geological ages. The faunas
of Africa and South America as a whole are thoroughly dis-

* Ortmann, A. E., “ Tertiary Archhelenis,” p. 242.
t Pocock, R. I., “ Distribution of Arachnida,” p. 229.
{ Kraepelin, K., “ Scorpiones and Pedipalpi,’’ p. 240.

ie at

»

VON IHERING’S RESEARCHES 383

tinct. All the more modern families of these continents show
scarcely any traces of relationship to one another. Conse- —
quently we must conclude with Dr. Ortmann and several other
authors who have definitely expressed themselves on the geo-
logical age of the former land bridge between South America
and Africa, that the latter ceased to exist before Tertiary
times.

Dr. von Ihering* did not limit his studies in South America
to the fauna, he likewise urged, contrary to the opinion
held by most botanists, that the floras of South America and
Africa pointed unmistakably to the existence of his ‘ Arch-
helenis.” ‘His arguments were so convincing that Professor
Engler + adopted his views after a very careful and critical
examination of the problem from a botanical aspect. He ac-
knowledged that for a long time he had looked upon the theory
of a former land connection between South America and Africa
with scepticism, chiefly on account of the great intervening
ocean depths and the marked endemism in the flora of the two
continents. After discussing the various means of accidental
dispersal, and eliminating those plants which might possibly
owe their presence in both continents to some of the known
modes of occasional transport, he was impressed by the cir-
cumstance that there was still a residuum of species, genera
and families which must have had another origin. He urged
that the distribution of the Strelitzioidae, whose fruits cannot
be dispersed by wind, also that of some of the water plants of
Africa, which have very near relations in South America, and
others might be accounted for by the supposition of the former
existence of a series of large islands in the Atlantia Ocean
separated by narrow channels. All the same he prefers a
complete land bridge between the two continents.

Dr. Arldt { discusses the problem in a very effectual manner |
both from a biological and a geological point of view. Like
Dr. Ameghino, however, he is led to the conclusion that even

in early Tertiary times South America was still directly joined

* Thering, H. von, “ Das Neotropische Florengebiet.”

+ Engler, A., “ Floristische Verwandtschaft zwischen Afrika and
Amerika,” pp. 50—351.

{ Arldt, Th., “ Entwicklung der Kontinente,” p, 451,

384 ORIGIN OF LIFE IN AMERICA

to Africa, whereas I favour the theory that such a connec-
tion could only have persisted indirectly by way of the Antilles
and southern Europe.

It has been urged that if a land bridge had once existed
between Brazil and west Africa we ought to find some traces
of sedimentary rocks on the few islands that are scattered
about in the intermediate area, like Fernando de Noronha, St.
Paul’s, St. Helena, Ascension and Tristan da Cunha, whereas
all these are believed to be composed of volcanic rocks. Pro-
fessor Schwarz,* nevertheless, affirms that although Ascen-
sion consists of voleanic rock the substratum is granitic. St.
Paul’s island, he thinks, is mainly metamorphic in structure,
and there are signs of its having been subjected to considerable
earth movements. Continental types of rocks occur on Tristan
da Cunha. Consequently Professor Schwarz concludes that
these Atlantic islands furnish some geological testimony for
the belief in a Mesozoic Continent in the position of the
southern Atlantic lasting until the beginning of the Tertiary
Era.

The island of Fernando de Noronha lies about two hundred
miles east of Cape San Roque on the coast of Brazil. Since
its discovery in 1503 both the original fauna and flora of the
island have been laid waste by early settlers, so that only
vestiges of these are left. The splendid trees that once clothed
the island are gone and with them probably the greater part
of the fauna. A mammal, at any rate, existed on Fernando de
Noronha when it was discovered, but it has quite vanished.
Mr. Ridley, who visited Fernando de Noronha in 1887, noticed
that quite a number of species of animals and plants had evi-
dently been introduced by human agency. Many others, he
thinks, have been transported to the island from the main-
land by winds, although he noted that the smaller birds and
a large proportion of the smaller insects are endemic. A few,
he remarks, may possibly have been brought over on the feet
of wading birds. There still remains a small group of indi-
genous species which are difficult to account for, on the hypo-
thesis of accidental distribution. The subterranean lizard

* Schwarz, E. H. L., “ Land-connection between Africa and ‘uth
America,” pp. 81—90.

FERNANDO DE NORONHA © 385

Amphisbaena ridleyi, for example, is peculiar to the island,
its nearest relation living in the West Indies. The skink
(Mabuia punctata) occurs on the island as well as in British
Guiana. The snail Bulimulus ridleyi, as I have already
pointed out (p. 176), is the only living representative of the
Oligocene group of species which once inhabited Florida.
There are, moreover, two species of Opeas identical with West
Indian forms, while a Pupa seems closely allied to a Cuban
species. The single fresh-water species (Planorbis noron-
hensis) is endemic. The noteworthy relationship with the
Antilles is also noticeable among the plants as well as among
the marine forms living on the shores of the island. As might
be expected, this is attributed by Mr. Ridley * to the action
of sea-currents. No other theory of the origin of the fauna
and flora of Fernando de Noronha than that of accidental
dispersal by wind or waves ever occurred to him. Yet both
Mabuia and Amphisbaena are genera which, as I have shown,
can be cited with some justification as evidences of the exist-
ence of a former land connection between South America and
West Africa. And these, with a gecko of enormously wide
range, constitute the only members of the reptilian fauna.
Why should these ancient reptiles inhabit Fernando de
Noronha and not any of the more modern groups? ‘This
and other pertinent criticisms of Mr. Ridley’s theory have
also been urged by Dr. von [hering,+ who shows, especially
from a botanical point of view, that accidental dispersal has
not played a very important part in the origin of the island
flora. On the contrary, he maintains that it is part of the
ancient Archhelenis which once united South America and
Africa.

The small island of Trinidad, not to be confounded with the
island of the same name in the West Indies, lies much further
south, and about seven hundred miles east of the coast of
Brazil. It is now uninhabited, though for a time it contained
a small colony of settlers who left a few goats and pigs on the
island, which continued the destruction of the native fauna
and flora commenced by their late masters. The ground

* Ridley, H. N., “ Zoology of Fernando Noronha,” pp. 473—502.
+ Ihering, H. von, “Fernando de Noronha,’’ p. 6.

L.A. cc

386 ORIGIN OF LIFE IN AMERICA

moreover, is riddled with the burrows of myriads of land
crabs, which have aided the domestic animals, to the best of
their ability, in this work. ‘Trinidad seems to have been
densely wooded formerly with tree ferns, palms, etc., whereas
living trees are now confined to the mountain tops. Among
the ferns collected on the island by Dr. Copeland * there was
one (Asplenium compressum) hitherto only observed in St.
Helena. Of the fauna nothing appears to be known. .
Ascension island lies in about the middle of the southern
Atlantic. When Darwin visited the island during his famous
voyage round the world, he found little there of interest. A |
principal mound in the centre looks as if it were the parent of
the lesser voleanic cones studded round the island. The sur-
face is parched and barren, and everything presents a scene
of utter desolation. Yet not only is Ascension island in-
habited, the scanty pasture has even been made serviceable
for a number of sheep, goats and cows. Ascension stands on a
submarine bank about two hundred miles in length. It is
probable on that account that the existing island only repre-
sents the last remnant of a cluster of volcanic cones which
rose high above the surrounding land. The surviving fauna
and flora are extremely poor. Many of the species, like the
centipede Scolopendra morsitans, are almost cosmopolitan in
their range, a few also occur in Africa or South America.
But no effort has as yet been made to conduct a thorough
zoological and botanical survey of the island, and it is to be
hoped that this will be accomplished before all traces of the
ancient relicts that might still occur have been superseded
by recent importations. At any rate, nothing of any impor-
tance can be gathered from the little information we possess.f
St. Helena, like Ascension island, is wholly volcanic in ©
structure, and being, moreover, surrounded by depths up to
17,000 feet, Dr. Wallace claims that we ought to be satisfied
as to its being a true oceanic island and as to its owing none of
its peculiarities to a former union with any continent or other
distant land. But, as I have pointed out once before, the exis-
~ a tence of such a great depth of the ocean does not prove that it

. Copeland, R., “ Insel Trinidad,” pp. 274—277.
+ Ginther, A., and others, “ Collection made in Ascension Island.”

ST. HELENA AND ITS FAUNA 387

does Not prove, nor even point to, a permanence of the great
depths, at least in the oceans of the Atlantic type. No longer
can we, therefore, subscribe to Dr. Wallace’s statement that
St. Helena is necessarily what he calls a “true oceanic
island.’”’ The island was densely covered with a luxuriant
forest vegetation when it was discovered in the year 1501.
Human occupation has almost wholly destroyed this in-
digenous vegetation, and with it no doubt the greater part of
the fauna. The rich soil, no longer protected by the covering
vegetation, has been swept away by tropical rains, leaving a
vast expanse of bare rock or sterile clay. Fortunately the
fauna and flora of St. Helena have received greater attention,
than those of Ascension, and although a mere fragment only of
what originally inhabited this area, it allows us to draw some
conclusions as to their origin. There are neither mammals,
amphibians nor reptiles on the island. The only indigenous
bird is a small plover (Aegialitis sanctae-helenae), closely allied
to a species found in South Africa. Among the invertebrates
the beetles in particular have been carefully studied by Mr.
T. V. Wollaston.¢ Out of two hundred and three species
collected on the island, he considers one hundred and twenty-
nine to be indigenous. Only one of these is found else-
where. These species belong to thirty-nine genera, of
which no less than twenty-five are peculiar to St. Helena,
most of them being weevils (Rhynchophora). Since the
greater number of weevils are woodborers, we conclude
from this fact alone that the island once possessed a luxuriant
forest vegetation. Many of the beetles show no close affinity
with any existing insects. A small number only are more
or less remotely related to European and South African
species. These features imply, as Dr. Wallace truly remarks,
that the beetle fauna of the island is extremely ancient, dating
back to at least the Miocene age. Dr. Wallace acknowledges
that at present the marine currents flow towards St. Helena
from the region of the Cape of Good Hope; nevertheless he
contends that in former geological periods the currents may

always was so. Geological evidence, says Professor Suess,* |

* Suess, E., “ Are Ocean Depths Permanent ?’’ p. 186.
t+ Wollaston, T. V., “Coleoptera Sanctae Helenae.”

cc 2

388 ORIGIN OF LIFE IN AMERICA

have varied, and that drift-wood might have been carried to
the island from different directions. Great alterations of
wind, he thinks, were probable during the Glacial Epoch, so
that these two most potent agencies in the accidental trans-
port of species may have varied very much during the periods
in which the island received its colonists from other countries.
Of course, Dr. Wallace* firmly adheres to the belief that all
animals and plants found on the island owe their existence
there to some means of occasional transport.

Thirty species of bugs (Hemiptera) have been recorded by
Dr. White from St. Helena, of which five have certainly, and
one probably, been introduced. This leaves twenty-six species
indigenous to the island. Of the twenty-one genera of Hemip-
tera eight are peculiar to St. Helena, but the general
distribution of these insects was so little known at the time
that Dr. White was unable to trace their affinities, except that
most of them have a wide range, and several are known from
Miocene deposits. Only one genus (Megarhaphis) has dis-
tinctly African affinities. Dr. White} argues from the
general aspect of the fauna and flora, from the non-existence
of mammals and reptiles, from the large number of endemic
species, and from the great depth of the surrounding sea, that
St. Helena at no time could have been joined by land with
Africa or South America. A careful consideration of all the
known facts led him to believe that the colonists did not arrive
all in a body, but that colonisation was spread over a con-
siderable period. He rejects the theory of a continuous land
surface, contending that the fauna and flora arrived from the
north in the direction of the Cape Verd islands. Stepping-
stones in the shape of islands, now disappeared, may have
existed formerly, thus facilitating dispersal, whilst the
marine currents were probably reversed.

Mr. Pickard-Cambridget informs us that forty-four species
of spiders are known from the island, some of them being also
found in Europe, and two in Egypt. The rest are endemic,
but most of them show European relationship. In a former

* Wallace, A. R., “Island Life,” pp. 294—303.
+ White, F. B., “ Hemiptera of St. Helena,” pp. 446—460.
t Pickard-Cambridge, O., “Spiders of St. Helena,” p. 210.

THE INSECTS OF ST. HELENA 889

ncte he recorded two scorpions (Lychas maculatus and L.
americanus). These have since been shown to be both forms
of Isometrus maculatus, a cosmopolitan species of the tropical
and sub-tropical zone. In Europe it occurs only in the south
of Spain.*

The total number of land-shells indigenous to St. Helena
is estimated by Mr. Smith as amounting to twenty-seven
species. With regard to their origin, he likewise rejects the
theory of a possible land connection of the island with either
Africa or South America, or, indeed, any other land surface.
All the same, he points out that there is a greater resemblance
between the molluscan fauna of St. Helena and South
America than was recognised by previous observers. It is
especially a species resembling the exclusively Brazilian —
genus Tomigerus that seemed to Mr. Smith to point to South
America as the likely source of some of the indigenous species.
He does not feel tempted to probe further into this mystery,
for he exclaims, ‘‘ How they were transmitted is a hopeless
problem to solve, and although drift-wood, carried by oceanic
currents, is doubtless answerable for a good deal in the way
of distribution the subject must apparently ever remain one
of mere speculation.’’ Nevertheless Dr. Kobelt + regards it as
highly probable that this molluscan fauna is the last remnant
of that of an ancient Mesozoic continent.

About half of the species of the snails of St. Helena are
now extinct and occur only in a sub-fossil condition. Hyalinia
cellaria, H. alliaria and a few others, along with Amalia

(Milax) gagates are supposed to have been introduced with

plants. It is quite possible that some of them were brought
to St. Helena in that manner, still it is very remarkable that
the only slug thus conveyed should be one of our rarest
British species, and the one which has the widest range of all
slugs. It occurs in California, New Zealand, and other remote
localities, while none of our common Arions, Agriolimaces
or Limaces have found their way to the island. I am fully
convinced that Amalia gagates is one of the most ancient of
our Kuropean terrestrial species, as I explained in a previous

* Pickard-Cambridge, O., “ Spiders and Scorpions of St. Helena,” p. 544,
+ Kobelt, W., “‘ Zoogeographische Stellung von St. Helena,”’ p. 201.

390 ORIGIN OF LIFE IN AMERICA

chapter (p. 218), and that it might well form part of the
indigenous fauna of the island. There are twelve species,
some of which greatly resemble Polynesian forms, as Mr.
Smith pointed out, and, indeed, Dr. Pilsbry has placed them
provisionally with Endodonta, a genus otherwise confined to
Australia and Polynesia. There are three species of Succinea,
a genus which seems to be particularly unfit for transport
on drift-wood, while the most striking members of the snail-
fauna are a species of Bulimus, seven species of Bulimulus,
and one provisionally placed by Mr. Smith* in the South
American genus Tomigerus.

More recently, Dr. Pilsbry demonstrated that these
apparently bulimoid snails are really members of the family
Achatinidae, and that they all belong to the genus Chilonopsis.
Since all the nearest relations of Chilonopsis are African.
genera, the affinity of this group is with Africa rather than
with South America. But the great antiquity of Chilonopsis

is indicated by the fact that Trichodina, to which it is closely |

allied, has a most remarkably discontinuous range, occurring
only on some islands off the coast of West Africa and on the
Comoro islands in East Africa. Chilonopsis, moreover, is
more primitive than the genera of the large African Achati-
nidae, and Dr. Pilsbry} expresses the opinion that-it, as well
as the related genera, originated from a common ancestor
which lived in Mesozoic times, when Africa and South
America were united by land. None of the species have any
affinity with South African ones, as was supposed to be the
case among the Hemiptera.

Although Dr. White’s Megarhaphis hus now been shown
to belong to Macrorhaphis, a genus confined to Africa,
two species have since been taken in west Africa.
The supposed slight affinity of the St. Helena bugs to
those of the Cape has therefore entirely disappeared. As
regards the pronounced European element in the St. Helena
insect fauna, it is probably to a large extent of American
origin. The beetle Zophobas morio lives, outside St. Helena,
only in west Africa, Central and South America and

* Smith, KE. A., “ Land-shells of St. Helena,” pp. 259—269.

+ Pilsbry, H., “ Manual of Conchology (Pulmonata)” (2), Vol. XVIL.,
pp. 171—173.

ee!

ANTIQUITY OF INSECT FAUNA 391

the Antilles, while all other members of the genus are
American. The only relation of the bug Metacanthus con-
color of St. Helena occurs in Europe, whereas the three most
closely allied genera inhabit America. The genus Nysius
has a world-wide range, and is known from American Miocene
deposits. Cardiastethus occurs in Europe as well as in St.
Helena, but the genus is mostly American, and from there
ranges across the Pacific to New Zealand. Nabis capsiformis
occurs in southern Europe, and also all over Africa and
America, while the genus has a world-wide range. The allied
Vernonia of St. Helena has near relatives in the West Indies
and the western Pacific region. Salda is a distinctly northern
genus, although a few species reappear far southward of
the others in Chile, New Zealand and St. Helena. That such
a range implies great generic antiquity is evident, and,
indeed, Salda is known in several species, from the lower
Oligocene.

Of the Curculionidae which are so largely represented in the
fauna of St. Helena, and which Dr. Wallace thought might be
of Miocene age, many recent genera are now known from the
Lower Oligocene and they are probably much older even than
that, for, according to Dr. Handlirsch, over two hundred
species are now known from Oligocene deposits. The genus
Homalota which Dr. Wallace fancied was exclusively Euro-
pean, is represented in the Oligocene of North America.
Philonthus, Xantholinus and Oxytelus occur in the American
Miocene. and European Lower Oligocene. The supposed
Huropean genera of insects inhabiting St. Helena are thus
mostly groups of very wide range, or such of which
we actually possess palaeontological evidence of their having
existed since early Tertiary times.

However ancient the insect fauna may be, remarks Dr.
Wallace, the flora must be more ancient still. Of the fifty
truly indigenous flowering plants, about forty are peculiar
to St. Helena, and of twenty-six ferns, about ten. The re-
lationship of this flora is mainly African, according to Sir
Joseph Hooker, whereas Mr. Bentham maintains that the
Compositae have their affinities for the most part with South
America, Sixteen species of ferns are common to St. Helena

392 ORIGIN OF LIFE IN AMERICA

and other countries. Dr. Wallace,* however, acknowledges
that specific identity among ferns does not necessarily imply
a recent origin. According to Professor Engler + the five
endemic genera are somewhat related to American ones,
whereas some species of Pelargonium, Mesembryanthemum,
Wahlenbergia and Oteospermum must have originated in
Africa.

Dr. von Ihering ¢ discusses all the various modes of dis-
persal, by birds, winds and ocean currents, in connection
with the origin of the flora of St. Helena, and rejects them
as quite inefficient. In his opinion, only a land connection
with Africa and South America could have produced the flora.

Although St. Helena is surrounded by great ocean depths,
and possesses neither mammals, reptiles nor amphibians, we
cannot assume, as Dr. Wallace has done, that the whole fauna
and flora owe their origin to accidental dispersal by birds,
winds and ocean currents. If such were the case, there is no
reason why these modes of transport should not have been

equally effective in Pliocene and Pleistocene times than in the ©

older geological periods, and why there should not be many
species differing but slightly from American or African ones.
Everything, on the other hand, points to the animals and
plants ‘being almost all of extreme antiquity. We have either to
suppose, therefore, that during some very remote period the
modes of transport alluded to were far more efficient than they
are now, or that St. Helena was connected by land with South
America and Africa. For many reasons, already fully dis-
cussed in this chapter, the latter hypothesis appears to me
the only one that is at all probable. If we assume that there
was such a land bridge, it is quite possible that the actual
volcanic area now forming St. Helena was not in existence,
but originated after portions of the land connection had
already subsided. A mere remnant of the fauna and flora
would eventually have taken refuge on the rock of St. Helena,
whilst the surrounding country disappeared beneath the
floods. Whether in early Tertiary, or even in later Tertiary
times, there was a short and independent land bridge between
* Wallace, A. R., “ Island Life,” pp. 305—307.

+ Engler, A., “ Entwicklungsgeschichte der Florengebiete,” IT., p. 179.
t Ihering, H. von, “ Das neotropische Florengebiet,” p. 50.

TRISTAN DA CUNHA 398

St. Helena, Ascension island, the Cape Verd islands, the
Canaries and Madeira, is a matter which must be left to future
observations. Certain faunistic features appear to be in
favour of such a theory.

Tristan da Cunha is almost as large as St. Helena. It
lies considerably further south, being bleak and inhospitable
in the extreme, owing to its proximity to the northern boun-
dary of the antarctic ice-drift. The flora is quite different
from that of St. Helena, as it possesses antarctic affinities.
The genera Nertera, Uncinia and Acaena inhabiting antarctic
America, New Zealand or Australia occur here also. It has
Lomaria alpina, in common with South America, Kerguelen
island, New Zealand and Australia, while Spartina arundi-
nacia occurs in Tristan da Cunha and St. Paul, and is related
to a South American species.* The most remarkable member
of the fauna is the genus Tristania which, with its two species,
is confined to the island. It is related to the snail Opeas which
inhabits both Africa and South America.

Almost three hundred miles further south there is still an-
other volcanic island, of which scarcely anything was known
until it was visited by Dr. Bruce, the leader of the Scottish
National Antarctic Expedition. First called ‘‘ Diego
Alvarez ’’ according to Dr. Brown,} its name was later on
changed to ‘Gough island.” The island differs from some
of the other islands referred to, in being densely covered with
vegetation, which is similar in character to that of Tristan
da Cunha. While showing the same general affinities, Diego
Alvarez seems to have a stronger American element than the
islands forming the Tristan da Cunha group. The land birds
comprising two species of bunting (Nesospiza) and a galli-
nule (Porphyriornis) are peculiar to the island, but related
to species living on Tristan da Cunha. :

To briefly review the results of our studies so far, it appears
highly probable that Brazil was entirely separated from
western South America in Mesozoic and part of Tertiary
times, but was connected with the highland of Guiana across
the mouth of what is now the Amazon river, which flowed

* Engler, A., “ Entwicklungsgeschichte der Florengebiete,” II., p. 159,
t+ Brown, R, N. R., “ Diego Alvarez,” pp. 9—10,

: a
e.* : : :
weed

394 ORIGIN OF LIFE IN AMERICA

westward. During part of Secondary times eastern Brazil
was most likely united by land with West Africa. During the
Cretaceous age already, the southern Atlantic rapidly advanced
northward, invading eastern Brazil, so that the land bridge
then joined only northern South America and a small tract
of West Africa. In EKocene times the southern trans-Atlantic
land connection had ceased to exist, yet the South American
continent must have extended still far eastward of its present
coast-line. Eastern Brazil continued to receive new additions
to its fauna from the northern States of South America while
its area extended gradually westward. When Brazil finally
became joined to Argentina a faunistic interchange took
place, although Brazil and Chile remain to the present day
two fundamentally distinct countries.

CHAPTER XV
ARGENTINA AND CHILE

AutTHouGH the natural southern boundaries of Brazil appear
to be the great river Plate and the Paraguay river (Fig. 18),
the two smaller republics of Uruguay and Paraguay are inter-
posed between Brazil and this river system, while Argentina
has also claimed a large slice of territory on the northern side
of it. As we proceed southward from eastern Brazil the moun-
tains gradually pass into hills which again are replaced by
gently undulating plains. Magnificent pasture lands abound
in Uruguay, accompanied by a mild and healthy climate, so
that the country is well adapted for the staple industry,
which consists in raising horses and cattle. The spurs of
the eastern highlands of Brazil are still recognisable in the
northern provinces of Argentina, where they are covered by
extensive forests of algaroba, cedar and other trees, thus
greatly adding to the natural resources of that wealthy
country. The surface of the remainder of the great Argen-
tine Republic is largely occupied by somewhat monotonous
tracts of low and nearly level land, here and there relieved by
small groups of mountain ranges which seem mostly to have
some connection with the foothills of the Andean mountain
chain. The whole of western Argentina again is very moun-
tainous and well wooded. The highest summit of the Andes,
Aconcagua (23,080 feet), actually lies in Argentine territory.
Beyond the crest of this immense mountain chain, occupying
an elongated narrow strip of country along the shores of the
Pacific Ocean, lies the Republic of Chile. The upheaval of
the Cordillera of the Andes, separating the two states, must
have been the result of movements of the earth’s crust which
occurred long after the formation of the rocks composing the
range.

With these alterations in the topography and climate as

396 ORIGIN OF LIFE IN AMERICA

we proceed southward, the fauna and flora gradually undergo
a complete change. On leaving the forest, monkeys, sloths
and other animals, bound to an arboreal life, are replaced by
new types, unknown in Brazil, such as the Patagonian hare
and vizcacha. A very characteristic faunistic feature of the
Argentine “‘ pam'pas,’’ as the humid grassy country is called,
is the presence there of the American representative of the
ostrich. ‘This rhea is quite absent from the vast forests of
Brazil. In the northern parts of that country, however, where
we again meet with grass lands, this flightless bird reappears
as a memento of the times when north and south were joined
by continuous prairies. We thus have some noteworthy
instances of discontinuous distribution suggesting a former
period when the drying up of vast lakes, perhaps, may have
given rise to grass lands, which enabled certain southern types
to push northward. Other Argentine animals, such as the
coypu (Myocastor ‘coypus), one of the largest of the rodent
tribe, have apparently invaded Brazil in more recent times,
for they have only entered the southern and western pro-
vinces. To those unacquainted with the past history of South
America it must come as a matter of surprise that the only
ungulate which is noticed in these vast pampas of Argen-
tina is a deer, closely related to the true North American deer
(Odocoileus virginianus) and its allies. I have expressed my
belief above (p. 111) that the true American deer owe their
origin to one or more ancestors which passed into South
America directly from Europe, and it is important to note
that the centre of dispersal of the various groups in South
America lies in the western states. Only a couple of species
are peculiar to Brazil. All the others are more or less
confined to the western states. Even the distribution of the
South American wolves led Dr. von Ihering * to the similar
conclusion that these animals entered the continent from the
west.

Mr. W. H. Hudson f gives us a vivid idea of the life in the
pampas of Argentina, the striking poverty of its fauna as
compared with Brazil, and all the more characteristic features

* Thering, H. von, “ Siidamerikanische Raubtiere,” p. 162.
t,,Hudson, W. H., “ Naturalist in La Plata.”

THE FAUNA OF ARGENTINA © 397

of that remarkably fertile country, which has lately become
a centre of attraction, not only from a point of view of
agriculture, but as a treasure-house of palaeontological
records. |

Argentina must have undergone very notable physio-
graphical and climatic changes within the Tertiary Era. As
Dr. White * has pointed out, the whole of the coast-line from
Rio de Janeiro southward appears to present evidences of
submergence. Rivers, bays and islands exhibit an aspect
of drowning similar to that shown by the rivers and bays of
Nova Scotia, Cape Breton and Newfoundland; and the amount
of coastal depression seems to increase southward, judging ©
by borings for harbour works at Rio de Janeiro and at
Pelotas.

The presence of terrestrial and fresh-water deposits to a
depth of nearly a thousand feet below the city of Buenos
Aires implies, as Dr. Ameghino + remarks, that here also the
continent extended formerly much further eastward. The
same author contends, in fact, that the whole of the southern
Atlantic is of Tertiary age. I am not prepared to concur in
this view, but it can scarcely be doubted that Argentina had
in later Tertiary times at any rate a much greater area than
at present.

It is now more than twenty years since Dr. Ameghino first
made known to the world that an extraordinary wealth of
animal life once tenanted the vast plains of Argentina. Not
only in early Tertiary deposits; even in late Mesozoic beds
were found the bones of mammals belonging to many different
groups. The origin of life, at least of the higher animals, was
always looked for in the north. Dr. Ameghino’s discoveries,
which certainly rank among the most noteworthy that have
ever been made in palaeontology, riveted attention for the
first time to the southern hemisphere. No wonder that Dr.
Ameghinof{ in his enthusiasm pronounced Argentina to be
the original home of all the mammals of the world.

* White, I. C., “ Relatorio final de estudos das minas,”’ p. 3.

+ Ameghino, FI, “ Formations sédimentaires, p. 29.

t Ameghino, Fl., “South America as the Source of Mammalia,”
p. 260.

398 ORIGIN OF LIFE IN AMERICA

Naturally his views gave rise to a considerable amount of
discussion and criticism among geologists and palaeontolo-
gists; and many visited the scenes of these startling dis-
coveries. Almost all of them felt convinced that Dr.
Ameghino had wrongly interpreted the age of the deposits
alluded to. They thought that the fossiliferous beds described
must be much more recent than Dr. Ameghino supposed, and
that at any rate South America was certainly not the source of
all the mammalia. One of the richest of the deposits exposed
in different parts of Patagonia, especially in the region of the
Santa Cruz river, and hence spoken of as the ‘“‘ Santa Cruz
beds,’’ is considered by Dr. Ameghino as of Upper Eocene
and Lower Oligocene age. Almost all other authorities believe
them to belong to the Miocene. The latter view seems to be
strengthened by the results of the study of the marine shells
contained in beds of similar age which were pronounced by
Dr. Ortmann * to be of Miocene Age. As Professor Scott +
expresses the opinion that Dr. Ortmann has clearly demon-
strated the Miocene age of the Santa Cruz beds, I should like
to direct attention to a more recent work dealing with this
problem. Its author, Dr. von Ihering,{ has made a special
study for many years past of the marine mollusks of South
America. Hence his opinion is of particular value. After
a long and careful study of a larger series of fossil mollusks
than was available before, he came to the conclusion that
the marine Cretaceous deposits of Patagonia pass very gradu-
ally into those of the next formation, which is the one
described by Dr. Ortmann, the latter scarcely containing
five per cent. of living species. He is inclined on that
account to agree with Professor Ameghino as to the Eocene
and Oligocene age of these marine beds, and thus indirectly
with his general scheme of correlation. Dr. von Ihering’s
arguments appear to me more convincing than those of Dr.
Ameghino’s opponents, and I shall therefore adhere to the
latter’s nomenclature of the Argentina deposits. Not only
has Dr. von Ihering adopted Dr. Ameghino’s views, they

* Ortmann, A. E., “Princeton University Expedition,’ Vol. IV.,
p. 317.

+ Scott, W. B., “ Mammalian fauna of Santa Cruz,” p. 241.
t Ihering, H. von, “ Mollusques fossiles de Argentine,” p. 95.

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AMEGHINO’S DISCOVERIES 399

have partially been accepted also by Dr. Roth,* who has
personally studied the problems on the spot.

As regards the mammalian remains contained in the Santa
Cruz terrestrial beds, Professor Scott + was greatly struck
by the strangeness of the assemblage. Not a single genus
occurs in any part of the northern hemisphere. Some of the
orders even of mammals are distinct from those of the
northern faunas. Thus the beds have yielded no carnivores,
no modern groups of ungulates nor elephants, while the
rodents all belong to the section Hystricomorpha. The place
of the carnivores was taken by carnivorous marsupials, some-
what resembling the Tasmanian wolf (Thylacinus). Numbers
of small plant-eating marsupials, of which Caenolestes
(see p. 850) is an interesting survival, likewise occur. One of
the largest, most varied and most characteristic elements of
the Santa Cruz fauna are the edentates. They are repre-
sented by the Dasypoda or armadillos, the greater part of
whose skin is strongly ossified, the scutes forming a great
shield over the body, and by the Glyptodontia and the Gravi-
grada. The last two groups are now extinct. The glyptodonts
resembled armadillos, except in so far as the bony scutes were
joined into a solid mass like the shield of tortoises, while the
Gravigrada or ground sloths were extraordinarily varied and
numerous. Only a single genus (Necrolestes) of Insectivora
has been obtained in the Santa Cruz beds, as already alluded
to (p. 246). At present this order is quite unknown in
South America. The ungulates belong to the extinct groups
Toxodontia, Astrapotheria and Litopterna. The toxodonts
were represented by the genus Nesodon which somewhat re-
sembled a rhinoceros in shape and had similar teeth. Of the
second group very little is as yet known, while the Litopterna
are the most remarkable of all the hoofed animals. Without
being in any way related to the horse-tribe, certain genera
have paralleled the structure of the horse-foot in a most
wonderful way, giving the latter a striking and deceptive re-
semblance to that of the ancient Hipparion. The animals
afford, indeed, as Professor Scott remarks, one of the most

* Roth, S., “ Sedimentablagerungen in Patagonien.”
T Scott, W. B., “Mammalian fauna of Santa Cruz,” pp. 242—247.

400 ORIGIN OF !LIFE IN AMERICA

remarkable and instructive examples of convergent develop-
ment among mammals. Finally the Santa Cruz beds contain
the remains of monkeys of South American type. The earliest
traces of mammalian remains in Patagonia were supposed to
have been found together with the bones of dinosaurs. Since
these reptiles are characteristic of the Mesozoic Era, the state-
ment that they were contemporaneous with rather advanced
types was at first treated with little credence, especially as
the actual deposits were not examined by Dr. Ameghino *
but by his brother. Dr. Roth, however, has since re-examined
the localities in question and has met with mammalian re-
mains partly mixed with those of dinosaurs, and partly resting
actually below the latter, so that there is scarcely any doubt
as to the correctness of the original observation. The
mammals belong to peculiar mastodon-like ungulates, having
been placed in the order Pyrotheria which is now extinct and
quite confined to Patagonia. Others, such as Notostylops, be-
long to the Toxodontia above alluded to.

I think there is a general agreement now that, at any rate
at the dawn of the Tertiary Era, a number of rather
specialized groups of mammals lived in Patagonia, and,
although some of them became extinct, others continued
to inhabit the country until recent geological times. A few
of the largest edentates, like the giant ground sloth Mega-
therium, which was about the size of an elephant, and is
supposed to have dragged down trees in order to feed on the
leaves, rather than climb up like its modern diminutive rela-
tion the tree-sloth, still roamed about the country in
Pleistocene times.f A few years ago the dried skin, with hair
still attached to it, of a huge creature was discovered in a cave
in southern Patagonia, near the boundary between Argentina
and Chile. It proved to belong to the ground sloth Neomy-
lodon, now known as Grypotherium listai.f Later on, the
bones of the animal were disinterred, along with those of an
extinct horse and a large carnivore. Traces of a fire were
also noticed and an enclosure with cut hay. From these evi-

* Ameghino, F1., ‘“ Formations sédimentaires,” p. 80.
+ Lankester, Ray, “ Extinct Animals,” p. 172.
t Moreno, F, P., and A. Smith Woodward, “‘ Neomylodon listai.”’

FOSSIL EDENTATES 401

dences of man’s presence, along with the remains of the
ground sloth, it was concluded that the cavern was an old
corral in which the ground sloths had been kept and tended
by some primitive human race.*

The survival of many of such large creatures until recent
geological times implies that, as in the northern hemisphere,
there must have been ample food available in Argentina
during the Pliocene and Pleistocene Periods to nourish these
mammals, the climatic conditions having since become more
varied and unfavourable. Compared with the Santa Cruz
edentates, the less ancient groups were mostly larger.

In spite of the fact that the fossil mammalian fauna, of
Argentina presents so many features pointing to long isola-
tion, the relationship of certain forms to those found in far
distant regions is of extreme interest and importance from a
zoogeographical point of view, as elucidating the geological
history of the South American continent. The diversity in
shape and character between the Santa Cruz armadillos
(Dasypoda), for example, is very notable, according to Pro-
fessor Scott,f no less than three families and seven genera
having been described so far. And yet a genus of armadillo
(Metacheiromys) makes its appearance in the Middle Kocene
beds of western North America. Dr. Wortman’s theory that
the edentates were of North American origin, having sub-
sequently spread to South America, has not been adopted by
any later authors. Dr. Wortman assumed that their earliest
appearance in South America did not antedate the Santa Cruz
epoch, whereas Professor Scott points out that they also
occur in the oldest known Tertiary and possibly even pre-
Tertiary deposits of Patagonia, and that there is every
appearance of their having been indigenous in that region.
It is, in fact, generally assumed now that South America was
the original home of the edentates. If it is correct, as I have
endeavoured to show, that Central America has only come into
existence in comparatively recent geological times, and that
the whole continent of South America in the dawn of the
Tertiary Era consisted of several distinct masses, Patagonia

* Woodward, A. Smith, “ Grypotherium listai,”’ p. 64.
+ Scott, W. B., “‘ Princeton Expedition to Patagonia,” Vol. V., p 7.
LeA. DD

402 ORIGIN OF LIFE IN AMERICA

at that time must have had a direct land connection with
western North America almost independently of the rest of
South America (Fig. 14). At a still earlier stage there was
even a more marked affinity between Patagonia and south-
western North America; and from this Professor Osborn con-
cluded that the northern and southern continents were con-
nected by land. But the points of resemblance are not alone
with Patagonia and south-western North America. Professor
Gaudry * expressed his astonishment at the striking faunistic
relationship between the Patagonian Notostylops fauna on the
one hand, and the faunas of the Torrejon in New Mexico and |
Cerney in France on the other. That a land bridge, discon-
nected at certain intervals, extended between western North
America and southern Europe I have urged again and again
in the preceding chapters; and it should be borne in mind
how, even in these remote times, special facilities existed for
the passage of species from Europe to the extreme south of
South America, which no doubt were taken advantage of by
several groups then inhabiting the Old World.

Until recently it was thought that North and South America
could have had no land connection subsequently to these early
events until the end of the Miocene or the beginning of the
Pliocene Periods. Professor Osborn, + however, has shown
that there is now evidence for the existence of true edentates
of the Megalonyx type in the Mascall beds of Oregon, which
are of Middle Miocene age. During the Miocene Period
Central America in its present shape had not yet come into
existence. Hence we may assume that even in Miocene times
there was a land connection between western North America
and some portion of South America by means of a route
which, as I argued, lay to the west of that continent.

The rodents of the Santa Cruz fauna, as previously men-
tioned, all belong to the section Hystricomorpha. They are
very closely allied, according to Professor Scott, to recent
South American genera. Yet all are extinct and many of
them have left no successors. Nevertheless, though the Santa
Cruz rodents are more primitive, the skull structure is nearly

* Gaudry, A., “ Fossiles de Patagonie,”’ p. 105.
+t Osborn, H. F.,, “‘ The Age of Mammals,” p. 289.

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FOSSIL RODENTS } 403

the same as in the recent ones. There is reason to believe, —
says Professor Scott,* that several of the genera represent
the direct ancestors of existing forms. Viscacha was probably
derived from Prolagostomus, Dolichotis from Schistomys,
Erethizon and Coendu from Steiromys. As regards the latter,
it is interesting to note that it resembles the recent Erethizon
more than it does the modern South American genera
of the same family. It seems to me probable, therefore,
as I have already suggested (pp. 69—71), that the South
American and North American tree porcupines originated
from two distinct branches of ancestral Steiromys-like rodents,
thus favouring the view I advocated of a direct land connec-
tion between Patagonia and south-western North America.
That the genus Erethizon, to which all the North American
porcupines belong, should not be known from pre-Pleistocene
deposits presents, no doubt, a difficulty to the acceptance of
this theory, but its ancestors may have remained on the last
remnants of the land which once existed westward of North
and South America until compelled to leave that land in Plio-
cene times, when it finally subsided.

The Santa Cruz fauna likewise reveals an affinity with the
fauna of Australia and Tasmania. The Patagonian marsupials
are referable to three families, remnants of which survive in
widely separated parts of the world. The Thylacinidae, now
confined to Tasmania, where the Tasmanian wolf represents
the family, formerly inhabited both Patagonia and Australia.
As we might expect, the Santa Cruz thylacines are of a more
primitive type than the Tasmanian wolf, but Professor Sinclair
expects that the common ancestor of these two will probably
be found among the marsupials occurring in still older Pata-
gonian deposits. ‘The opossums (Didelphyidae), among which
Microbiotherium is the best known, are met with in several
genera in the Santa Cruz beds. The Cretaceous Proteo-
didelphys suggests, as I have already mentioned, that South
America must be looked upon as the original home of the
family whence some members passed into North America and
Kurope. I have briefly alluded to the occurrence in Ecuador

* Scott, W. B., “Princeton Expedition,” Vol. V., pp. 384—886 and
p. 413.

DD2

404 ORIGIN OF LIFE IN AMERICA

of the marsupial Caenolestes and to its being the only living
member of the extinct family Epanorthidae. Inthe Santa
Cruz beds this and another family of herbivorous marsupials
are represented by several genera. Professor Sinclair * in-
clines to the belief that the South American Epanorthidae and
the ‘Australian phalangers have had common ancestors. From
all these facts he concludes that a land connection between
Patagonia and the Australian region must have existed not
later than the close of the Cretaceous Period or the beginning
of the Tertiary Era, and that the interchange of marsupials

may have been effected between the two continents at this |

time. |

Of all the similarities between the South American and
Australian extinct faunas none perhaps is more striking, re-
marks Dr. Smith Woodward,f than the essential identity of
the extinct Miolania in the two regions. He thinks there can
be no doubt that this creature was a truly terrestrial or marsh
chelonian. The theory of a former land connection between
South America and Australia seems, therefore, to receive
weighty support from the new discovery of this curious
reptile.

It has also been urged that the Patagonian fossil fauna
indicates traces of an affinity with South Africa. Professor
Scott,f with some hesitation, expresses the opinion that the
resemblance of the solitary Patagonian insectivore Necrolestes
to the golden mole Chrysochloris of South Africa may be due
to genetic relationship. It is significant, in view of the early
Tertiary faunistic relationship of Patagonia and western
North America, to note that certain creatures resembling the
golden moles made their appearance in North America in
Oligocene and Lower Miocene times. I have had occasion to
allude to Xenotherium and Arctoryctes already (p. 246). The
affinities between these various forms are not very marked. At
any rate, it would be unsafe to draw any conclusions as to the
existence of a former direct land bridge between Patagonia
and South Africa from the presence of Necrolestes in the
Santa Cruz deposits.

* Sinclair, W. J., ‘“‘ Marsupial Fauna of Santa Cruz,” pp. 76—81.

+ Woodward, A. Smith, ‘“ Extinct Reptiles from Patagonia,” p. 182.
t Scott, W. B., “ Princeton Expedition,” Vol. V., p. 379.

FAUNISTIC AFFINITIES 405

Professor Tullberg’s* reference to a pre-Tertiary land
bridge between South America and south-west Africa is not
very definite. From his remarks it is not clear that he is in
favour of the existence of an independent connection far to
the south of the one I discussed in the last chapter.

These are among the more important results derived from
the study of the fossil fauna of Argentina as to the affinities
presented by this part of South America to the more distant
parts of the world. We have still to consider the faunistic
kinship between Argentina and the neighbouring states of
South America. Dr. von Ihering } pointed out long ago that,
whereas America as a whole is the richest part of the world
in the variety of genera and species of fresh-water mussels,
Chile and Peru belong to the poorest districts, since, at any
rate west of the Andes, only the genus Unio occurs. Similarly
Ampullaria and many other typically American fresh-water
genera are absent from Chile. On the other hand, the Unios of
Chile are most of them nearly related to those of the La Plata
region. Dr. von Ihering { concludes from these very peculiar
zoographical features that, while the whole of southern South
America (Archiplata) formed a united land-mass in Secondary
times, the elevation of the Andes afterwards prevented a
faunistic interchange between the two districts. The fresh-
water crustacea tell us a very similar story. The fresh-water
crayfish Parastacus is met with in eight species in South
America.§ None of them occur north of southern Brazil,
although several of the Chilean species are closely related to
Brazilian ones. The fresh-water crab Aeglea laevis, no doubt
an exceedingly ancient form and the only representative of the
family Aegleidae, lives in identically the same species on both
sides of the Andes. The absence of almost all the leading
genera of Brazilian fishes from Chile and Patagonia,|| empha-
sises the noteworthy distinctness in the fresh-water fauna of
the two regions. On the other hand, Patagonia and Chile
present traces of a relationship, as I intend to show later on,

* Tullberg, Tycho, “ System der Nagetiere,’’ p. 495.

t Ihering, H. von, ‘‘ Verbreitung der Ampullarien,” p. 106.

} Ihering, H. von, “ Archhelenis and Archinotis,” p. 57.

§ Ortmann, A. E., ‘ Distribution of Decapods,”’ pp. 292—296.

|| Higenmann, C., “ Freshwater Fishes of Patagonia,’ pp. 227—229.

406 ORIGIN OF LIFE IN AMERICA

with western North America, with southern Africa and with
New Zealand and Australia.

As we ascend the Andes from northern disenitioar we meet
with a familiar animal-which we generally associate with Peru
and its inhabitants, namely, the llama. The llama is only a
domestic animal. But its wild ancestor the huanaco (Lama
huanachus) still exists plentifully in the Andes of Peru and
Chile, as well as in the plains of Patagonia. Its western dis-
tribution, like that of the bear, some of the deer and many
vertebrates and invertebrates, is thus very marked and de-
mands an explanation. For the benefit of those who may |
be unacquainted with the pedigree of this creature I may men-
tion that the huanaco and its domesticated relations the llama
and alpaca, are essentially camels in structure. There are
certain differences in the teeth, the huanaco being with-
out a hump and smaller than the camel, while the head is
more like that of a sheep. But the shape and structure of the
skull and bones and the general anatomy are very similar
in the huanaco and camel, implying that they have descended
from the same ancestor. The occurrence of the camels in Asia
and of the llamas in South America is a case of widely dis-
continuous distribution of two related genera and thus points
to an ancient origin. The geological history of the family is
of the greatest interest. The first member of the camel tribe
makes its appearance in Argentina in a deposit known as the
Lower Pampean, which Dr. Ameghino considers of Pliocene
age, though some authorities think it is more recent. Here
occurs Palaeolama, an extinct ancestor of the huanaco. In
the upper portions of the same deposit the remains of quite
a number of llama-like creatures have been discovered such
as Protauchenia, Hemiauchenia, Stilauchenia and Mesolama,
as well as the huanaco itself. That is about all we know of the
past history of these camel-like animals of South America.
The fact that no members of the family are known from earlier
deposits than Pliocene, and that the extinct genera are nearly
related to the living one, suggests that the ancestors of the
huanaco were not originally native to South America but in-
vaded the continent from elsewhere. Africa and Hurope no
longer were connected with South America. North America
is thus the only possible source whence the ancestral huanacos

THE LLAMA AND ITS PAST HISTORY 407

or llamas could have originated. And that is precisely what
happened, as already mentioned (p. 86). Towards the
latter end of the Eocene Period there appeared four genera
in western North™AtMerica, all of which exhibit decidedly
camel-like characters, and Professor Osborn * believes that
one of these, the diminutive Protylopus, may possibly repre-
sent the most remote ancestor of the grand American phylum
of camels. Other genera occur in Oligocene and Miocene beds
of North America. During the latter period camels had ap-
parently spread in great herds over the continent. It is
thus probable that they then extended their range to other
parts of the world. Some of them, like Pliauchenia, had
assumed llama-like characters, and as the western Pacific land-
belt was then in communication with California the ances-
tors of the South American llamas were able to pass south-
ward. According to Professor Osborn llamas survived in
North America until Pleistocene times. They were then
becoming extinct in the eastern States, lingering on in Cali-
fornia where the great sabre-tooth tiger no doubt.stalked them.
In the Siwalik beds of northern India camels first appear in
the Pliocene, as in South America, and it is generally assumed
that the ancestors of the Old World camels crossed over to
Asia by the Bering Strait land bridge. But as it was probably
in Miocene times that these early camels wandered westward
from North America, the Bering Strait land bridge had not
yet come into existence. They must have utilised the more
southern bridge, which I think replaced it in earlier Tertiary
times (Fig. 16).

Recently we have received clear proof of a migration of
mammals from Asia to North America, which I think must
have taken place across the same Pacific land bridge. One
of the most remarkable discoveries among the many note-
worthy ones in North American palaeontology is that by Dr.
Matthew and Mr. Cooky of Asiatic antelope remains in
western Nebraska. The American invasion by true Asiatic
- antelopes was brilliantly and amply confirmed, according to
Professor Osborn, by Mr. Merriam’s discovery in Nevada.

* Osborn, H. F., “ Age of Mammals,” p. 170.
+ Matthew, W. D., and H. J. Cook, “Pliocene Fauna from Nebraska.”

408 ORIGIN OF LIFE IN AMERICA

Rather earlier arrived in North America the mastodons,
and no doubt by the same Pacific land connection. They in-
vaded the continent from’ Asia and remained until Pleistocene
times, being thus co-existent with the early races of man in
America. That they travelled beyond North America, pene-
trating far into the southern continent, has been clearly de-
monstrated. A large number of apparently distinct forms have
been described from South America, most of them, as we
should expect, from the west coast, though it is very doubtful
if more than a few species lived there. Dr. Nordenskiéld
thinks that Mastodon chilensis, M. bolivianus and M. andium
all belong to one species. In North America, as in Europe,
both the trilophodont and tetralophodont types of mastodon
have been discovered, that is to say, animals which possessed
intermediate molar teeth with either three or four ridges.
In the South American Mastodon andium, at any rate, the
molars are in the transition stage between the trilophodont
and tetralophodont types. These extinct elephants made their
first appearance in Argentina in the Lower Pampean deposits.
Since they had thus penetrated so far south in early Pliocene
times they must have left North America before Central
America had come into existence. They could only have
wandered southward along the southern continuation of the
Pacific land bridge and have entered the South American
continent from the west during the time the bridge was joined
to the latter. Dr. Nordenskiéld * argues that, having no more
efficient competitors in South America, the mastodon probably
lived longer there than in North America.

Hitherto the theory has been quite generally accepted that
the invasions of animals from North America to the southern
continent, during later Tertiary and Pleistocene times, took
place across the narrow isthmus of Central America as soon
as its formation was completed. Some doubts have latterly
been raised as to the nature of the barrier which prevented
the interchange of the two faunas in the earlier portion of
the Tertiary Era. Yet until the discovery of gravigrade sloth
remains in the Miocene Mascall beds of Oregon was announced
by Professor Sinclair, the assumption seemed perfectly justi-

* Nordenskidld E., “Saugetier-fossilien des Tarija Tals,’ pp. 14—25.

RANGE OF; FOSSIL ELEPHANTS: 409

fied, from all available data, that North and South America
became joined at the commencement of the Pliocene Period.
It was supposed that the advance of northern types, such as
the mastodon and hosts of others, towards the southern con-
tinent must have coincided with the opening up of the new
land of Central America. The occurrence of edentate remains
in North American Miocene deposits upsets this theory,
because, if mammals were able to reach North America from
the south during the Miocene Period, northern species must
have had equal facilities for invading South America at this
time. If there is geological evidence that Central America was
not available as a safe land bridge between North and South
America in Miocene times, some other land connection
must have united the two continents. When I advanced the
theory of the former existence of a Pacific land bridge between
North and South America, westward of Central America,* I
was unaware of Professor Sinclair’s interesting discovery
among the Mascall beds of Oregon. My theory was largely
founded on zoogeographical data—on curious instances of
discontinuous distribution of ancient groups in North and
South America. Professor Osborn + regards my theory as
inconsistent with the fact that the Pacific land bridge should
only have been used by these gravigrade sloths. If such a
land connection really existed why was it not more exten-
sively used ? I think it was used by other animals, such as the
mastodons and the ancestors of the llamas to pass southward,
and by the ancestors of the North American tree porcupines
in entering North America.

Since I wrote my essay on the problem of a former land
connection, other than the Central American one, between
North and South America, I have had opportunities of study-
ing the subject more at my leisure. I find that the affinity
existing between south-western North America and the
extreme south of South America among some of the more
ancient groups of animals is greater than I thought. Let
us examine this curious relationship between the two
widely separated faunas a little more closely. I explained

* Scharff, R. F., ‘“ Early Tertiary Land-connection.”
t Osborn, H. F., “ Age of Mammals,” p. 292.

410 ORIGIN OF LIFE IN AMERICA

(p. 120) that the mammals inhabiting Patagonia and south-
western North America in late Mesozoie and early Tertiary
times indicated the existence of a direct land bridge between.
these two areas. But the Patagonian land-mass must have
included Chile or such parts of it as were then above sea-
level. We know very little of the past fauna of Chile. If,
as I endeavour to prove, a portion of our living fauna is of
great antiquity, some animals should reveal unmistakable
signs of this early affinity of Chile with that of south-western
North America. I imagine, as previously stated, that the early
Tertiary land bridge connected Chile directly with western
Mexico and California. Hence we might expect that not only —
Chile and Patagonia, but the outlying islands of California,
as well as the Galapagos islands, ought to show a faunistic
relationship with one another. |

I have already alluded to the fact that three groups of the
snail Bulimulus inhabiting Chile and Peru, the Galapagos
islands and Lower California are very similar in their narrow
elongated shape, so that they were formerly considered to be
very closely related. Dr. Pilsbry* is now of opinion that this
similarity in appearance is not any evidence of near relation-
ship but a special parallel modification of different Bulimulus
stocks, or, as we might say, a case of convergence. He attri-
butes these cases to be products of similar environments. Yet
is the environment of Chile really so similar to that of the
Galapagos islands or Lower California ? Climatically and geo-
logically I should think there must be a good deal of difference
between these districts.

The relationship between the western North American snail
fauna and that of western and south-western South America
is well illustrated by the distribution of the genus Hpi-
phragmophora. This is a group of snails entirely confined to
Central America and the Pacific borders of North and South
America. It is important to note also that the majority of
the snails inhabiting the islands off the coast of California
belong to this genus. Cerros, Guadelupe, Santa Barbara,
San Clemente and other islands all have their peculiar species
of Epiphragmophora. Now the most interesting point about

* Pilsbry, H. A., “Manual of Conchology (Pulmonata),” X., p. 126.

ANCIENT LAND CONNECTIONS 411

the members of this genus is their astonishing resemblance,
as mentioned before, to certain species of the Huropean group
Helicigona, including the well-known Arianta arbustorum.
Some of the American shells are externally so much like the
latter that they were placed into the same genus until recently.
Dr. Pilsbry,* however, maintains that the European Heli-
cigona differ anatomically from Epiphragmophora, and that
the two should be placed in quite distinct groups. Even on
anatomical grounds opinions may differ very radically, for
Dr. von Ihering claims that the American Epiphragmophora
and the members of the group Helicigona are genetically con-
nected. After careful examinations of the Huropean Arianta
arbustorum and the Argentine Epiphragmophora tucuma-
nensis he could perceive no noteworthy anatomical difference
between the two, and placed them both into the same genus.
If Dr. von Ihering’s } observations are correct, this is another
example of the same extraordinary relationship between Huro-
pean and west American forms that I have had occasion to
point out in: previous chapters. Occasionally this relation-
ship manifests itself only in Europe and south-western North
America. In other cases it exists simply between Huropean
and western South American forms. In this case both the
American western centres are related to the Huropean centre
of dispersal. It clearly illustrates, as stated before, that
Europe was once joined to a mid-Atlantic land bridge which
communicated directly with a belt of land lying to the west of
America. On the disappearance of the latter many of the
animals inhabiting that belt of land took refuge in the western
parts of America and still persist there.
Epiphragmophora, all the same, does not clearly reveal the
special affinity that exists among the older forms of animal
life of south-western North America and southern South
America. The wingless insects known as “‘ bristle tails ’’(Thy-
sanura) are generally looked upon as a very ancient group.
Among these the genus Japyx, which is easily recognisable
by its forceps-like tail-appendage, has a noteworthy distribu-
tion. Japyx solifugus occurs in the Mediterranean region,

* Pilsbry, H. A., “ Manual of Conchology (Pulmonata),” IX., ba 195.
+ Ihering, H. von, “System der Heliciden,” p. 422.

412 ORIGIN OF LIFE IN AMERICA

whence it has spread as far north as southern Germany.
Several other species are peculiar to southern Kurope and
Madeira. One Japyx is found in India. Across the Atlantic
Japyx subterraneus has been observed in the Mammoth Cave
of Kentucky, while a second species (Japyx saussurel) inhabits
only Mexico and Chile.*

The curious scorpion-like Koenenia, the only genus of the
order Palpigradi, is confined, as already mentioned, to
southern Europe, Texas and Chile. As far as America is
concerned, it is limited in its range to the two regions alluded
to. The family of spiders, Mecicobothriidae, according to
Mr. Pocock,} occurs only in the western States of North
America and in Argentina, the genus Hexura being found in
the former and Mecicobothrium in the latter part of America.

The ancestral form of the evidently very ancient family of
earthworms, Megascolecidae, seems to be Notiodrilus. This
genus is met with in America only in Mexico, Guatemala,
Chile, Argentina, Patagonia, Tierra del Fuego and the Falk-
land islands, while another genus, namely, Kerria, inhabits
Lower California and southern South America, being absent
from the intermediate area. The slug Philomycus has a wide
range in North America, occurring in Mexico, Guatemala and
Costa Rica, and then turns up again far away to the south
in Chile. Similarly the salamander Plethodon, which in North
America inhabits principally the western States, is found in
a single district in South America, namely, in Argentina.
There are a large number of similar examples among such
forms of insects that we have reason to believe date back
to at least early Tertiary times. The best known example, per-
haps, is that of the common northern genus Carabus. In
Mexico there are still two species. Neither in Central
America, nor in northern nor middle South America has it
been discovered, while in Chile and Tierra del Fuego there
are nine species. That the latter are now considered suffi-
ciently distinct to be placed into the separate genus Cero-
glossus does not alter the fact that they are closely related
to northern Carabi, whereas they have no affinity at all with

* Karsch. F., ‘“‘ Neue Fundorte von Japyx,”’ p. 154.
t Pocock, R. I., “ Geographical Distribution of Spiders,” p. 346.

CHILE AND CALIFORNIA 418

any South American forms. The genus of Tenebrionidae
Apocrypha is quite confined to California and Chile. That
all these instances indicate the existence of a former direct
land connection between Chile and California, independent
of the rest of South America, as I have explained before, is
indicated by another example derived from the same family
of beetles. The three closely allied genera Arthrocomus,
Stomion and Kurymetopon occur respectively in Chile, the
Galapagos islands and California. |

Under this heading also comes an instance of distribution
which had not hitherto been noted and which was pointed out
by Mr. McLachlan.* He remarked that the family Limno-
philidae, a family of insects the larvae of which manufacture
those cases of twigs and straws, so abundant in northern
ponds and ditches, is not known to occur south of Mexico,
except in Chile and the Falkland islands.

It was Dr. Wallace,} I believe, who first drew attention,
as already noted in a previous chapter (p. 235), to the
remarkable fact that a large number of European and North
American genera, such as the butterfly Argynnis and the
running beetle Carabus, reappeared far south of the tropics
in Chile, Argentina and Tierra del Fuego. I also alluded
to his explanation of the manner in which this surprising
phenomenon had been brought about. He was under the im-
pression that this migration across the tropics had been
effected mainly during successive Glacial Epochs, when the
mountain range of the isthmus of Panama, if moderately in-
creased in height, might have become adapted for the passage
of northern forms, while storms would often carry insects
from peak to peak over intervening forest lowlands or narrow
straits of sea. Improbable as this theory may appear, it might
still be defended as long as we had to deal merely with the
occurrence in southern South America of a few northern
insects. But the phenomenon is, as we have seen, a much
more widespread one. It applies to earthworms, slugs, sala-
manders and even mammals, and it is evidently the result
of a dispersal which occurred long before the Glacial Epoch.

* McLachlan, R., “Insect Fauna of Chile,” p. 162.
+ Wallace, A. R., “ Geographical Distribution,” Vol. IL., p. 45.

414 ORIGIN OF LIFE IN AMERICA

It took place, in fact, in very remote times, probably during
the dawn of the Tertiary Era; and only such forms as were
capable of preserving their specific and generic characters
till the present day clearly reveal their northern origin.

The flora of the New World, as I remarked in the paper
just referred to, retains even more pronounced traces of that
curious relationship between the south-western areas of its
two continents.* As among the fossil mammals so do we
find also among the fossil plants, a remarkable affinity in late
Mesozoic deposits between species from Argentina and from
western North America. Professor Berry tells us that in |
mid-Cretaceous times seventy-five per cent. of the known
plants of Argentina were characteristic types of the Dakota-
group flora of North America. During a period of geological
history when a large section of the existing western part of
South America was under water, there was this extraordinary
similarity between two regions lying at such a great distance
from one another. Professor Berry justly argues that the
surprising affinity of these floras to one another points to a
community of origin. In these ancient plant deposits of
Argentina all the familiar northern genera such as Lirio
dendron, Liquidambar, Cinnamomum and Sassafras are met
with. Even Platanus, Populus, Quercus and other modern
genera are represented. No wonder that Professor Berry
came to the conclusion that a geographical connection must
have existed between North and South America during mid-
Cretaceous times. During Cretaceous and early Tertiary
times the genus Sequoia, to which the Californian red-wood
and big-trees belong, likewise ranged from North America to
Chile. And it is now held by many botanists that the fossil
Sequoia langsdorfi is identical with the still living big-tree
(Sequoia gigantea) of California. We possess no fossil testi-
mony of the occurrence of the smaller deciduous plants in
those remote times, but to judge from the fact that many of
the Mesozoic genera of trees still survive to the present day,
certain persistent deciduous species presumably did so too.
Mr. Engelhardt { records a number of plant remains from the

* Scharff, R. F., “ Karly Tertiary Land-connection,”’ pp. 523—526.

+ Berry, E. W., ‘“ Mid-Cretaceous Geography,” p. 510.
t Engelhardt, H., “Tertiarpflanzen von Chile,” p. 635.

—_S\ To

FOSSIL PLANTS OF ARGENTINA. 415

west coast of Chile which he considers to be of early Tertiary
age. Of these the greater portion, he thinks, belongs to still
existing species, though he hesitates, in the absence of further
evidence, to adopt the recent specific names. At any rate,
almost all are very closely related to species now living in
the:West Indies, Central America and Brazil.

There exists a very widespread assumption that no species
of animals or plants survive to this day from the Mesozoic
Era. As our knowledge of fossil animals increases, instances
accumulate of very close resemblance of Mesozoic species of
mollusks to those now living, while some genera certainly
date back to Palaeozoic times, so that we can no longer place
implicit faith in the old traditional belief. My own convic-
tion is that many species of the less highly organised groups
of animals have survived unchanged even from those remote
times to the present day. _We know that certain species of
plants such as Sequoia langsdorfi, and some of the Unios
among animals, have remained practically unaltered through-
out a series of geological ages. It seems equally possible
that others of whose geological history we know nothing have
likewise done so.

Professor Asa Gray and Sir Joseph Hooker * long ago
directed attention to the unexpected feature that many genera,
and even species of North American plants, recur in the dis-

tant regions of southern South America. More recently

Professors Engler,+ Bray and Hackel have dwelt on this re-
markable phenomenon, and have speculated on the problems
connected with it. The flora of the Rocky Mountains,
including the Sierra Nevada Mountains above the transition
zone, and the mountains of Chile and Argentina, though
separated from one another by a stretch of some ten degrees of
latitude of moist tropical country, abound in northern genera
of plants, such as Ranunculus, Anemone, Geranium, Spiraea,
Geum, Rubus, Saxifraga, Vaccinium, Gentiana, Hieracium
and others. The greater number of such plants occurring in
the southern continent are endemic, pointing to long-con-
tinued isolation. Yet certain species even of the Rocky

* Gray, Asa, and J. Hooker, ‘ Vegetation des Rocky Mountain Ge-
bietes,” p. 292,
+ Engler, A., ‘ Entwicklungsgeschichte der Florengebiete,”’ II., p. 256.

416 ORIGIN OF LIFE IN AMERICA

Mountain arctic alpine region reappear in the extra-tropical
Andes, being, so far as is known, wholly absent from the
Mexican Mountains as well as from the tropical Andes.
Among these Professor Bray mentions particularly Gentiana
prostrata, Trisetum subspicatum, Primula farinosa and its
variety magellanica, Draba incana, Alopecurus alpinus, Saxi-
fraga caespitosa, Polemonium microcanthum and Collomia
gracilis. Dr. Stapf kindly drew my attention to another
instance, namely, to the occurrence on the mountains of
Argentina, at a height of 10,000 feet, of the typically arctic
genus of grasses Phippsia. The similarity in the flora of the
two regions is by no means confined to mountain forms.
Some species of the western plains of North America also
reappear in the extreme south of South America. Thus the
monotypical saxifrage Lepuropetalon, a peculiar and some-
what abnormal genus, grows in damp low-lying meadows in
Texas. Yet far south on the coast of Chile the same species,
Lepuropetalon spathulatum is to be met with.

A few of these plants may possibly have been casually in-
troduced from the northern locality to the southern. But in
most cases, Professor Bray * thinks, we have to deal with
forms which were connected by a remote ancestry, and which
flourished at a time and under conditions permitting a more
general distribution.

What these conditions were like he does not venture to sug-
gest, but a direct land bridge between western North America
and Chile probably existed, as I suggested, in late Cretaceous
and early Tertiary times. To it, I think, the relationship
of the floras of these two widely separated areas to one
another, is mostly due. Whether many species of plants
have persisted to the present day from such remote times
we do not know. Some no doubt have, and, as already
stated, others, among them those alluded to, may have
done so. A large portion of this old western land, with
its mixture of a southern and northern fauna and flora,
evidently remained above sea-level until a much later geo-
logical period. The evidence derived from certain relict
land-areas of this Pacific land belt clearly shows that a

* Bray W. L., “ Relations of North American Flora,” pp. 709—716.

FLORAL AFFINITIES | 417

southern flora passed over them, for of course southern ©
plants penetrated northward just as animals did. Mr. Sereno
Watson,* for example, in referring to the flora of the small
island of Guadalupe off the west coast of California, remarks
that the presence of so many South American types suggests
that this, and the similar element which characterises the
flora of California, may be due to some other. connection be-
tween these distant regions than the one now existing. He
expresses the opinion, too, that all the peculiarities in the
western floras of both continents had a common origin in an —
ancient flora which prevailed over a wide, now submerged
area, and of whose character the former are the partial
exponents.

As regards the question whether the northern plants
growing in Chile and Argentina can really be regarded as
indigenous or introduced, Professor Hackel has recently dealt
with this problem from a new point of view. He shows that
the species which are either identical with European or North
American plants, or such as may be considered as varieties or
sub-species of them, increase rather than diminish as we go
further south. Thus he records fifty-one plants from
southern Patagonia and Tierra del Fuego belonging: to this
group, which he regards as undoubtedly indigenous to these
countries. Thirty others may possibly have been introduced
by man. Professor Hackel thinks that their southward
advance could only have taken place step by step on a land
surface. If. these plants had passed across Central America
and along the Andes, we should find relict colonies of the
species, or at least their modified descendants, scattered on
their route of migration. Only very few of such occur in
Bolivia, Peru and Ecuador, and these have the appearance
of having reached these localities from the south rather than
from the north. When we examine the composition of this
remarkable flora in the Magellan district, we notice, according
to Professor Hackel,+ that the majority of the species belong
to the grasses (Gramineae) and the sedges (Cyperaceae). The
dicotyledons only comprise fifteen species. This he believes

* Watson, Sereno, “ Flora of Guadalupe Island,” p. 112.
+ Hackel, E., “ Flora der Magellanslinder,” pp. cxi—cxv.
L.A. EE

418 ORIGIN OF LIFE IN AMERICA

to be due to the greater antiquity of the grasses and sedges,
and he argues in favour of an ancient direct land connection,
long since disappeared, on which the slow southward advance
of these forms took place, the identical species having pre-
served their specific characters throughout a long series of
ages. This is precisely the conclusion I have come to in
regard to many species of animals of very wide range, con-
trary to the view generally held that most of such forms are
to be regarded as human importations scattered throughout
, the world by commerce.

I have mentioned on several occasions that California ex-

tended considerably further westward in former times, and
that the numerous little islands such as Guadalupe, Cerros,
Santa Catalina, Santa Rosa and others are the visible remains
of that ancient Pacific land belt. The fact that they are in-
habited by fourteen species and varieties of reptiles and
amphibians* not known from the mainland, suggests that the
islands have. been separated from the latter since at any rate
pre-Glacial times.

Now on the coast of Chile we have similar evidence of a
westward extension of land in former times. The tiny deer
known as the “pudu’’ occurs in Chile and Chiloé island.
Its only near relative lives in Ecuador. The small mouse-like
mammal Acodon brachyotis of Chiloé island and the Chonos
archipelago is peculiar to these islands, and so are many other
species of the lower groups of animals. There is, in fact,
quite a considerable assemblage of animals and plants on
these islands, indicating a former westward extension of the
mainland. Even the far distant Juan Fernandez island,
which lies five hundred miles from the mainland, possesses a

peculiar species of humming-bird (Eustephanus fernan-.

densis) and no doubt other indigenous forms of animal life.
It is situated on the tract of the old land belt which I believe
to have once extended from the west coast of southern Chile
to south-western North America, and from there eastward
to Europe (Fig. 14). In early Tertiary times already parts of
this old land bridge had disappeared, so that Chile and south-

* Denburgh, J. van, “ Reptiles and Amphibians of Pacific Coast
Islands,”’ p. 4.

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ANCIENT PACIFIC LAND BELT 419

western North America became disconnected. Yet the eastern
shores of the great peninsula, which long afterwards stretched
southward from the west coast of California, joined the con-
tinent of South America further north, probably in Ecuador
and Peru (Fig. 16). Animals and plants arriving from the
north, like the mastodon above alluded to, no longer reached
Chile directly, though still able to enter South America by
this second route, which added many new forms to the fauna
of the continent.

This is all I have to say on the origin of the faunistic and
floristic relationships between southern South America and
North America as well as Europe. I have also referred
above to a kinship existing between the Santa Cruz fauna of
Argentina and the living fauna of Australia. This is a pro-
blem of even greater interest than that just discussed. At
any rate, the testimony in its favour has converted many of
those who had hitherto looked upon great changes in the
disposition of continents and ocean basins during the Tertiary
Era as altogether visionary speculations. Some, like Professor
Osborn,* who contends that the Atlantis hypothesis is highly
improbable, regard the hypothetical reconstruction of a great ,
southern continent (Fig. 21) uniting South America with /
Australia as one of the greatest triumphs of recent biological /
investigation. The theory of the former land connection be-
tween southern South America and New Zealand or Australia
has been discussed from almost every point of view, so that we
possess at present quite an extensive literature on the subject.
A few years ago Dr. Ortmann summarised the more important
papers dealing with this subject, but many other essays have
since been published throwing further light on this fascina-
ting problem. The great majority of those who have endea-
voured to account for the undoubted faunistic or floristic affi-
nities of southern South America and the Australian region
have come to the conclusion that it is due to the existence of a
former antarctic continent. A few, however, argue that there
was a more direct land connection between the two areas
across the southern Pacific, while some believe that the resem-
blance in the fauna and flora of the countries referred to has

* Osborn, H. F., “ Age of Mammals,’’ p. 75.
E EQ

420 ORIGIN OF LIFE IN AMERICA

arisen partly by accidental dispersal and partly by migration
through the existing continents, when. they were united by
short temporary land bridges in the far north.
Sir Joseph Hooker seems to have been the first to formulate |
the theory of a former land connection of southern lands from
the occurrence of identical species of plants in widely
separated areas. The first to mention an antarctic continent
in this connection was Professor Ruetimeyer. This was
twenty years later, in 1867. Six years elapsed after that until
Professor F. W. Hutton again brought forward the theory, ;
expressing his belief in the former existence of an antarctic
land-mass and its union with the southern extremities of the
present continents. A few years later Dr. Gill declared him-
self in favour of a large continental mass embracing Africa,
South America and Australia, his views being based on the
geographical distribution of fishes. The fact that Dr. Wallace
repudiated the opinions expressed by his predecessors need
not be taken too seriously. Since his great work on the geo-
graphical distribution of animals was issued, facts have been
' brought to light which are so overwhelmingly in favour of
some kind of continuous land connection between South
- America and the Australian region that he could not at the
present day assert, as he did then, that the affinities alluded to
/ are mostly due to accidental dispersal across the ocean, aided
by the presence of an antarctic land-mass unattached to other
continents. Professor Hutton subsequently abandoned his
theory of a land-bridge between the two regions by way of an
antarctic continent in favour of a land connection right across
the South Pacific towards the end of the Mesozoic Era.*
In the year 1891, an important contribution to the subject
was published by Dr. von Ihering.f He points out that the
species of fresh-water Unio from New Zealand and adjoining
countries have their nearest allies exclusively in Chile and
southern Brazil, and that the fresh-water crayfishes (Para-
stacidae) show the same character. The conclusions he de-
rives from these and other facts are that the southern portions

* Ortmann, A. E., “ Origin of Antarctic Faunas and Floras,” pp. 139—

140.
+ Ihering, H. von, “ Relations between New Zealand and South

America,” p. 442.

ANTARCTIC PROBLEMS | 421

of South America (Archiplata) extended southward in form
of a South Pacific antarctic continent, which kept this area
in communication with the Pacific continent during the whole
of Mesozoic times (Fig. 17). From the latter, became separated
first a number of Polynesian islands, then New Zealand and
finally Australia and New Guinea. Dr. von Ihering deals with
the same problem in several of his papers, some of which have
now been reprinted in his recent work entitled ‘“‘ Archhelenis
and Archinotis.’’* After giving a brief review of the main
features pointing in favour of a former antarctic continent
connecting the Australian region with South America, Pro-
fessor Jacobi + expresses himself in favour of the theory. A
great deal of additional evidence in support of the same view
was collected by Dr. H. O. Forbes.{ He cites many examples
among birds, the southern pikes (Galaxiidae), which occur in
Chile, Patagonia, the Falkland islands and New Zealand, the
family Cystognathidae among amphibians, and numerous
plants, as illustrating the intimate affinity existing between
the faunas of the Australian and South American regions.
He also traces a faunistic relationship between these regions
and the Madagascar area, and concludes that all these
southern land-masses were once joined to an antarctic con-
tinent. It is easy enough to vaguely describe such a land
connection. Dr. Forbes was not satisfied to do this. He
was the first to give a map clearly indicating how he
conceived that all the areas referred to were united with one
another.

Mr. Beddard § briefly discussed the problem in 1895.
While criticising Dr. Forbes’ evidence in so far as it relates
to the struthious birds and penguins, he admits that there
are very strong arguments in favour of a former land connec-
tion between Patagonia and the Australian region, particu-
larly when we take into consideration the distribution of
earthworms.

As Mr. Hedley aptly remarks, ‘““we may compare the
shattered biological monuments of Tasmania and South

* Thering, H. von, “ Archhelenis and Archinotis.”

+ Jacobi, A., ‘ Biogeographische Gebiete,’’ pp. 204—207.
t Forbes, H. O., “The Chatham Islands.”’

§ Beddard, F. E., “ Zoogeography,” pp. 161—172.

422 ORIGIN OF LIFE IN AMERICA

America to the broken columns found by Oriental travellers
in the ruined and deserted cities of a vanished civilisation.
And as an archaeologist may restore from such fragments the
fallen temples or disused aqueducts, so may a naturalist trace
the missing arches of life that once spanned the gap.’’ Mr.
Hedley * favours the theory of a direct land connection in
Mesozoic or early Tertiary times between Tasmania and
Tierra del Fuego across the South Pole, while New Zealand
then reached sufficiently near this antarctic land without join-
ing it, to receive by flight or drift many animals and plants.
He thinks the faint affinity of Antarctica to Africa would be
explicable on the supposition that before either America or
Australia had united with the former, Africa had already
broken away from it.

A very memorable discussion on this question took place
during the fourteenth annual meeting of the American
Society of Naturalists in Philadelphia. Reviewing the geo-
logy of the antarctic regions, Professor Heilprin + stated that
in its relation to the other continents there was reason to
believe that Antarctica, whether as a continent or in frag-
mental parts, had a definite connection. with one or more of the
land-masses lying to the north, and that the suspicion could
hardly be avoided that such connection was, if with’ nothing
else, with New Zealand (and through it with Australia) and
Patagonia. The facts of palaeontology are best explained,
according to Professor Scott on the assumption that the
antarctic land-mass has at one time or another been connected
with Africa, Australia and South America, all of which once
radiated from the South Pole, just as North America and
Eurasia now do from the North Polar area.

Although Professor Britton § cited many examples of
astonishingly close relationship between plants of Australia,
southern South America and South Africa, it is unnecessary
in his opinion to invoke as an explanation a former land con- —
nection across the antarctic region.

Arguing from the geographical distribution of the fishes,

* Hedley, C., ‘“ Surviving Refugees in Austral Lands,” pp. 3—6.
+ Heilprin, A., ‘Geology of Antarctic Regions,” pp. 306—307.

+ Scott, W. B., “ Antarctica Palaeontology,” p. 310.

§ Britton, N. L., “ Origin of Antarctic Flora,” p. 311.

ANTARCTIC CONTINENT 423

reptiles and amphibians, Dr. Gill* maintained that the evi-
dence in favour of a former antarctic continental area is
strong, and, in view of the affinities of the species of the now
distant regions, the conclusion is logical that the time of
disruption was not remote in a geological sense.

So far as existing mammals and birds are concerned, said
Dr. Allen,t+ there seemed to be very slight need for calling in
the aid of a former antarctic continent to explain their pre-
sent distribution. The distribution of marsupials alone
among mammals gave a hint of a possible former land connec-
tion between South America and Australia.

Mr. Ancey ¢ gives a valuable contribution to the subject
at issue, founded on the distribution of the terrestrial
mollusks. The results of his enquiries are that the evident
relationship of the faunas of South America and the Austra-
lian region can be satisfactorily explained by the assump-
tion of a former antarctic continent uniting these land areas.

As the antarctic problem has been widely discussed from
an ornithological standpoint, and since Dr. Forbes and Pro-
fessor Milne-Edwards have based their theories of former
land connections largely on the past and present range of the
flightless ratite birds, it is right to mention that Professor
Burckhardt § disagrees entirely with their conclusions. He
does not dispute the possibility of former antarctic land con-
nections, especially between New Zealand and South America.
But he does not consider that the flightless giant birds of the
southern hemisphere can in any way be regarded as furnish-
ing evidence in favour of the theory of a former antarctic
continent.

From a. zoogeographical point of view, inconspicuous
groups of invertebrates, such as the earthworms, are of far
greater value than birds are. When the older writers dis-
cussed the antarctic problems we knew as yet practically
nothing of their distribution. Within recent years several
zoologists have made a special study of this group, and have
found that earthworms are of the greatest value in the study

* Gill, Th., “ Fishes, Reptiles and Amphibians of the Antarctic,” p. 315.
+ Allen, J. A., “Birds and Mammals of the Antarctic,’ p. 317.

t Ancey, OC. F., “ Faunes malacologiques australes,”’ p. 27.

§ Burckhardt, R., ‘‘ Problem des antarktischen Schépfungscentrum.”’

2.

494 ORIGIN OF LIFE IN AMERICA

of palaeogeography. Professor Benham, moreover, has the
advantage of residing in New Zealand, so that his views on
these problems are of peculiar interest. To the south of New
Zealand, between the latter and the antarctic regions, there
are two groups of islands, viz., the Auckland and Macquarie
islands. Now it is a specially noteworthy fact, remarks Pro-
fessor Benham, that the species of earthworms from Mac-
quarie island, and those occurring in the Auckland islands, are
more nearly allied to South American and South African
species than to those of the mainland of New Zealand. ‘The
evidence derived from the distribution of earthworms is, ac-
cording to Professor Benham,* strongly in favour of the
theory that New Zealand, South America and South Africa
were once connected with one another by land.

A study of the fresh-water crayfishes yields an even more
remarkable testimony in support of the same view, at least
of the theory that New Zealand and southern South America
were connected by land. Dr. Ortmann points out that the
family of crayfishes known as Parastacidae is confined to
Australia, including Tasmania, New Zealand, southern South
America and Madagascar. This family has thus an extremely
discontinuous range and must be of great antiquity. Dr.
Ortmann 7+ believes that the Parastacidae existed in Australia
in Upper Cretaceous times and thence spread by a land con-
nection into Antarctica, from which Parastacus reached Chile.
Subsequently Parastacus extended its range to Argentina and
southern Brazil. Madagascar, he thinks, was not connected
with the Antarctic Continent, and received its fresh-water
crayfishes by another route. Besides this affinity in the fresh-
water crayfishes of the Australian region and temperate South
America, there are other crustaceans showing similar features.
Mr. Geoffrey Smith tells us that one of the commonest
plankton organisms in the mountain lakes and tarns of
Tasmania is the copepod crustacean Boeckella. Now this
genus nowhere spreads into the tropics, yet reappears in
New Zealand and southern South America.

* Benham, W. B., ‘‘ Geographical Distribution of EHarthworms,”’
pp. 329—835.

+ Ortmann, A. E., ‘‘ Distribution of Decapods,” p. 340.

{ Smith, Geoffrey, ‘‘ Naturalist in Tasmania,”’ p. 137.

PATAGONIA AND NEW ZEALAND 425

~ Professor Kolbe contributes a careful review of the subject

from the point of view of the beetles (Coleoptera). After
illustrating the intimate relationship that exists between
southern South America and the Australian region, by means
of the distribution of some of the Carabidae, Lucanidae, Scara-
baeiidae, Buprestidae, Elateridae and other families of beetles,
he comes to the conclusion that an Antarctic Continent must
have existed in early Tertiary times. Professor Kolbe * be-
lieves that this continent was joined to the southern parts of
South America, New Zealand and Australia, and that some
genera passed from the latter to America, whilst others
travelled in the opposite direction. Although the affinities
of South Africa and Madagascar with South America and
Australia are much less pronounced, Professor Kolbe never-
theless urges that these countries, too, were to some extent
connected by land with the Antarctic Continent.

Dr. Arldt} recently gave us an excellent summary of the
most striking points in favour of the theory that southern
South America and the Australian region were once con-
nected by means of an Antarctic Continent. The theory meets
with his entire approval, but he concurs with Professor

-. Hutton and others in the belief that a second means of com-

munication between Australia and South America was fur-
nished by a mid-Pacific land bridge.

Finally, Professor Chiltont reviewed the problem from the
point of view of New Zealand and the neighbouring sub-
antarctic islands and their fauna and flora. His conclusions
are strongly in favour of a former land connection by way of
the Antarctic Continent between South America and New
Zealand.

I have still to state my own opinion on this subject. That
there was some kind of a direct land connection between Chile
and New Zealand and Australia appears to me obvious. The
strongest arguments in its favour are supplied by the distri-
bution of the fresh-water mussels and the fresh-water cray-
fishes. The genus Diplodon, one of the Unionidae, inhabits

* Kolbe, H., ‘‘ Coleopteren der Magalhaensischen Sammelreise,”’
pp. 19—30 (compare also ‘‘ Die Siidpolarkontinenttheorie ”).

+ Arldt, Th., ‘‘ Bedeutung der Antarktis,” p. 370.

{ Chilton, C., ‘* Biological Relations of Sub-antarctic Islands,” p. 806.

426 ' ORIGIN OF LIFE IN AMERICA

the rivers of western and southern South America. No living
Diplodon has ever been discovered in Central or North
America, where other Unionidae are found in the greatest pro-
fusion. No Diplodon has ever been discovered fossil either in
Central or North America, although a great many fossil
Unionidae are known to science. Hence it seems certain that
Diplodon has never lived north of its present habitat. Yet
in New Zealand, in Tasmania and Australia this genus re-
appears. Further north in Asia it has never been met with.
Some zoologists are of opinion that affinities such as the one
alluded to can be interpreted by the supposition of a former —
sub-universal distribution and a subsequent extinction in all
but the present habitats. We do not possess a shadow of any
evidence for such a belief, in so far as the range of the fresh-
water mussel Diplodon is concerned.

Let us take the second case, that of the fresh-water cray-
fishes. Crayfishes are abundant in the streams of North
America and Asia, but they all belong to the family Potamo-
biidae, while southern South America is inhabited by quite a
different family, the Parastacidae. Crayfishes of the latter
family are again met with on the other side of the Pacific, but
only in the extreme south, in New Zealand, Tasmania and Aus-
tralia. Neither of these instances can be due to convergence, —
nor to a passage from one continent to the other by way of
the northern continents. A direct land bridge becomes abso-
- lutely essential, yet this need not necessarily have lain in the
direction of the antarctic regions. Its position might have been
further north, as suggested by Professor Hutton,* although
the latter has more recently revised his theories, in so far
as he now advocates two south Pacific land bridges, instead
of a single one as previously maintained. In 1905 he ©
announced that, having reconsidered his former conclusions, —
he believed that an Antarctic Continent existed in Jurassic —
times which connected South America with New Zealand and —

South Africa. He thinks that this continent sank in the Cre- |
taceous Period, Antarctica never having since been connected

with northern lands. Subsequently, either during Cretaceous |
or early Tertiary times, a Pacific Continent must have united —/

* Hutton, F. W., “ Ancient Antarctica,” p. 245.

PACIFIC CONTINENT 427

New Zealand with Chile, which, as he maintains, ceased to
exist at the close of the Eocene Period.

Certain geological features no doubt point to a former west-
ward extension of Chile. Dr. Burckhardt * showed that in
western Chile there are enormously thick deposits of porphy-
ritic conglomerates which become more attenuated and com-
posed of lighter sandy material as we proceed eastward.
Hence he argues that these deposits were laid down on an
ancient shore-line of a vast western land-mass of which the
existing coast cordillera of Chile is the last remnant. He
advocates, in fact, nothing short of what we might call a
Pacific Continent which lay mainly to the westward of Chile.
That land formerly extended in that direction I have en-
deavoured to demonstrate from purely faunistic evidence, but
I believe that it was part of a great circum-Pacific belt of
land which stretched mainly northward, communicating from
time to time with Central America and the Antilles, and also
with Mexico and western California, and then eventually, bend-
ing across to eastern Asia in a great loop and thus joining
New Guinea, Australia and New Zealand. That Central
America and western North America must have been thus
connected by land with the Australian region has been urged
above on several occasions when dealing with the North
American fauna. It might be argued that if such a northern
land connection once existed, uniting Chile with the Austra-
lian region, there would no longer be any necessity for postu-
lating an antarctic land bridge. Professor Dahl has recently
taken up this attitude, illustrating his adverse criticism against
the antarctic theory by means of the distribution of spiders.
He does not adopt, of course, my view of a northern semi-
circular land belt because this theory has never before been
published and is entirely my own. His contention is that the
continents and oceans have remained within the lifetime of
the present. fauna what they are now, that is to say, within
the more recent geological periods, except that the great land-
masses were joined in. the north. A powerful centre of dispersal
existed in the arctic regions, according to Professor Dahl.t

* Burckhardt, C., ‘‘ Traces d’un ancien continent,’”’ pp. 186—190.
+ Dahl, F., ‘‘ Die Verbreitung der Spinnen.”’

428 ORIGIN(0F LIFE IN AMERICA

and ‘from it streamed forth practically all life, which eventually
reached the most southern tips of the continents. We thus not
only find there the oldest forms congregated together, accord-
ing to Professor Dahl, but these would naturally resemble one
another in all the southern parts of the continents. It is
a simple theory, and at first sight, as I mentioned before,
when discussing the similar views of Dr. Haacke, it seems
-to put before us the solution of all the problems of dispersal
in a satisfactory manner. No one, however, who has taken
the trouble to read this book, can for a moment, I venture to
think, perceive any justification for holding such a belief as —
that of Professor Dahl’s. There may possibly have been such a
centre of dispersal as that suggested, but it was long before
any geological records existed. Any forms of animal life that
we are acquainted with show clearly and unmistakably that
there have been scores of great centres of dispersal in the
world, and that from them streamed forth new forms in every
available direction. Northern animals advanced southward
and southern forms northward, aided, no doubt, by the ever-
changing conditions of climate and the gradual evolution of
oceans and continents.

To return to the question at issue, let us examine what light
the marine fauna throws on the problem. The geographical
distribution of the elephant seal (Macrorhinus leoninus),
which occurs on the shores of southern South America, of
the antarctic lands, of New Zealand and Tasmania, will not
contribute much to its solution, but some of the inverte-
brates are of more importance. The Hocene beds of Pata-
gonia, as well as those of New Zealand, contain several species
of marine mollusks common to both, such as Cucullaea alta,
Scalaria rugulosa and Turritella ambulacrum. Other Pata-
gonian species, for example, Brachydontes magellanica, Tur-
ritella patagonica and Crepidula gregaria only appear in New
Zealand in later deposits. Besides these species the older
Tertiaries of the two countries have a large number of genera
common to both. Dr. von Ihering * thus concludes with con-
siderable justification that the geographical conditions during
early Tertiary times must have been favourable for a dis-

* Thering, H. von, ‘‘ Mollusques Fossiles de L’Argentine,” p. 499.

MARINE FAUNA OF PATAGONIA 429

~persal of marine mollusks. between Patagonia and New Zea-
land. It is interesting to note that, whereas this faunistic
interchange took place between Patagonia and New Zealand,
the early Tertiary Chilean fauna exhibits scarcely any traces
of relationship with that of New Zealand.

If the ancient land connection between southern South
America and New Zealand had been a westward extension of
the coast of Chile, we should expect a greater resemblance
between the old Tertiary fauna of the latter country and New
Zealand than between Patagonia and New Zealand. The evi-
dence derived from the Eocene mollusks of Patagonia and
New Zealand is, therefore, in favour of a southern land con-
nection by way of the antarctic regions. I cannot believe that
an Antarctic Continent, in the sense of Forbes or Osborn,
could have existed at that time. If the affinity of the marine
faunas of Patagonia and New Zealand was due to a con-
tinuous shore-line between the two countries, Chile must
‘have extended southward beyond Tierra del Fuego and then
have curved across to New Zealand in a great loop. The Pata-
gonian fauna spread to New Zealand on the south side of the
latter. Hence the South Polar region must have been largely
covered by sea at that time. At any rate, I believe in the
former existence of two land connections between Chile and’
New Zealand, one by way of North America and eastern Asia,
the other directly across the South Polar area.

This leads us to the third problem connected with that
extraordinarily interesting region of southern South America,
namely, its direct affinities with the anntarctic regions, and in-
cidentally with South Africa and Madagascar. The southern
tip of Tierra del Fuego bends eastward. At its eastern ex-
tremity lies Staten island, and beyond it the great Burdwood
Bank. North of the latter, at no great distance, are situated
the Falkland islands. Nowhere is there a greater depth of
water than a hundred fathoms between the latter and the
mainland. Consequently all this presumably was once part of
South America.

The Falkland islands cover an area of about half the size
of Ireland, lying three hundred and fifty miles east of Pata-
gonia. The country consists of undulating moorland, with an -
abundance of peaty soil yielding an ample supply of wiry

430 ORIGIN OF LIFE IN AMERICA

grass with a growth of bushes here and there. As Darwin
pointed out long ago, almost the whole of the islands are com-
posed of sedimentary rocks, such as clay-slate and sandstone,
while the hills are formed of white granular quartz. Darwin *
considered the sandstone of Silurian age, whereas Mr.
Newton,} who has recently examined the fossils brought back
by Dr. Bruce, shows that they belong to the Devonian Period,
many of them being identical with South African species of
similar age.

No clue, however, can be obtained from the geological fea-
tures as to the age of the islands, or, as we might say, the
time when the latter became separated from the mainland.
We are thus obliged to seek for information from the exist-
ing animals and plants. Mr. Vallentin’s { account of the
fauna and flora only deals with the general features, such as
a casual visitor might notice. He informs us that no indi-
genous mammals occur on the Falkland islands, as the peculiar
wolf (Canis antarcticus) which once lived there is now ex-
tinct. It is still customary to connect this Falkland island wolf
with some of the inainland species, although Mr. Lydekker §
pointed out long ago that it differs markedly from all the dog-
and wolf-like creatures (Canidae) of South America, being
closely allied to the North American coyote (Canis latrans).
Dr. von Ihering || places it, along with the coyotes, into the
sub-genus Lyciscus, whereas the remaining South American
species of the family belong to Chrysocyon, Carcinocyon and
other genera. Neither of these writers dwell upon the causes
of this altogether extraordinary range. Are we to regard this
as an instance of convergence ? I scarcely think that any —
mammalogist will maintain such a view. And yet how are we ~
to account for the fact of the existence in these remote islands
of a mammal whose nearest relatives are all confined to North
America ? It is an extremely interesting problem. I have
alluded to the noteworthy fact more than once that Chile, and —
even Tierra del Fuego and Argentina, exhibit avery surprising —

* Darwin, C., ‘“‘ Journal of Researches,” p. 142.

+ Newton, E. T., “ Fossils from Falkland Islands,” p. 251.

t Vallentin, R., “* Voyage to the Falklands,” p. 352.

§ Lydekker. R., “ Geographical History of Mammals,” p. 140.

|| Ihering, H. von, ‘‘ Verbreitung d. Siidamerik. Raubtiere,” p. 153.

THE FALKLAND ISLANDS. 431

faunistic relationship with western North America, but this
affinity seems to be confined to very ancient groups of verte-
brates and invertebrates. I ventured to allude to the North
American porcupines as being possibly the descendants of
Steiromys, which I suggested had utilised the early Tertiary
land connection from Chile to Mexico or California. Stei-
romys, however, is long since extinct. If we suppose the
coyotes to have taken advantage of that land connection in
early Tertiary times, we might assume a member of that early
fauna to have succeeded in surviving in these lonely islands
until recent times. But the difficulty in accepting such an
hypothesis is that it would give the coyotes a much longer
ancestry than any palaeontologist would care to admit. Never-
theless it is the only theory I can suggest. Another question
that occurs to me is—If the wolf was the only mammal in-
habiting the Falkland islands, what did it live on ? Wolves are
carnivorous, as everyone knows, usually feeding on smaller
mammals. Yet Darwin states that it is the only quadruped
native to the islands ; he adds, however, in a footnote, “‘ I have
reason to suspect there is also a field mouse.’’ This is probably
a species of Reithrodon or some allied genus. Still this
mouse-like creature could scarcely have constituted the sole
food of such a large animal as the wolf. In all likelihood,
some larger rodent existed on the islands and may have
become extinct before the advent of man. The wolf soon after
this event shared the same fate.

An examination of the earthworm fauna, which is probably
of very great antiquity, reveals the fact that there are living
on the Falkland islands two species of the genus Noteo-
drilus (N. bovei and N. falclandicus) which otherwise is con-
fined to South and Central America, New Zealand, Australia,
Cape of Good Hope, Madagascar and several of the antarctic
islands. A second genus, viz., Chilota, which is represented on
the Falkland islands by Chilota daleti, inhabits only southern
South America and the Cape of Good Hope, with the exception
of a single species living on the Cape Verd islands. The third

genus, Yagansia, has not yet been found on the Falkland
islands. It is almost peculiar to Chile and Argentina. Only

one species of Yagansia has been met with in South Africa.*
* Michaelsen, W., “ Verbreitung d. Oligochaeten,” p. 74.

432 ORIGIN OF LIFE IN AMERICA

Thus there appears to bea distinct faunistic affinity between
southern South America as a whole, including the Falkland
islands, and New Zealand, as well as South Africa and Mada-
gascar. I have already alluded to Professor Bouvier’s * re-
markable discovery of the Peripatus of Chile being more
closely allied to that of South Africa than to those of the rest
of South America, so that he now places the South African
and Chilean species into the genus Opisthopatus, while all
the rest remain in the old genus Peripatus. I have likewise
drawn attention to the fact that the family of fresh-water cray-
fishes Parastacidae occurs only in southern South America, the
Australian region and Madagascar. Professor Kolbe} argued ©
long ago that the manifold faunistic affinities of South
America and Madagascar were largely due to an immigration
into the latter of American forms from the south by means
of antarctic land connections. Lastly, there are relationships
even among the marine forms of Patagonia and South Africa
which seem to demand the existence of a former direct land
connection between these areas, although Dr. Ashworth ¢
would join ‘the latter to an Antarctic Continent. When ,the
faunas of Madagascar and South Africa become better known,
it will be possible to follow these clues with greater success.
That these affinities are altogether of the nature of con-
vergences, as some authorities would have us believe, is, I
think, inadmissible. If they are due to the existence of
former antarctic land connections, we may be sure that they
are of very great antiquity, possibly far beyond the limits of
the Tertiary Era.

Stimulated largely by these zoogeographical problems, the
antarctic regions have within recent years received a greater
share of public attention than hitherto. Thus expeditions
have been fitted out from Belgium, France, Germany, Eng-
land and Scotland in order to endeavour to throw light on
some of these mysteries. Interesting results in connection
with the theories of a former land connection between
South America and Madagascar were obtained, particularly
by the Scottish Antarctic Expedition. Returning northward

* Bouvier, E. L., ‘‘ Monographie des Onychophores,”’ pp. 64—68.

+ Kolbe, H. J., ‘‘ Zoogeographische Elemente in Madagascar,” p. 173.
{ Ashworth, J. H., “ Arenicolidae of South Africa,” p. 23.

ANTARCTIC EXPEDITIONS 433

from the South Polar regions, Dr. Bruce took a series of
soundings proving that the South Atlantic rise extended
a thousand miles further south than was previously known.
Now Dr. Bruce believes that this comparatively shallow
water area extends westward to the Sandwich group (not
to be confounded with the Sandwich islands in the Pacific
Ocean), and eastward to Bouvet island. By demonstrating
the presence of a long ridge of about three hundred miles
in breadth between Madagascar and Bouvet island to the
Sandwich group, with a forked connection towards the South
Orkneys and the antarctic regions on the one hand, and the
Falkland islands and Tierra del Fuego on the other, Dr.
Bruce * has made a valuable addition to our knowledge of the
zoogeographical affinities referred to.

Professor Carpenter,+ who described the Collembola brought
back from the South Orkney islands by the Scottish antarctic
Expedition, concludes that these minute insects support the
view of the former existence of extensive land tracts south of
the American continent. It may be mentioned incidentally
that sedimentary rocks have now been discovered not only in
the South Orkney islands by Dr. Pirie, but also in the island’
of South Georgia.

A very important contribution to the subject of the
antarctic problem is that by Dr. Enderlein. He deals with
the geographical distribution in the South Polar regions
of insects as a whole. Chile, Tierra del Fuego, the Falk-
land islands and South Georgia all belong, according to him,
to Dr. von Ihering’s ‘“‘ Archiplata’’ region, while the Auck-
land isles, Campbell islands and the Macquarie islands are
grouped as part of New Zealand. The former has a large num-
ber of endemic genera of insects. Dr. Enderlein regards the
family Thynnidae as one of the most valuable supports in
favour of a former land connection between Archiplata and the
whole Australian region, all the females of this family of
Hymenoptera being wingless. ‘These insects are confined to
the Australian region and southern South America. Numbers
of similar instances are cited. After quoting all the recorded

* Bruce, W. S., “Survey of South Atlantic,” p. 10.
+ Carpenter, G. H., “* Collembola from South Orkneys,” p 479.

L.A. FF

434 ORIGIN OF LIFE IN AMERICA

insects from the antarctic regions, Dr. Enderlein comes to
the conclusion that the existing features of distribution are
best explained by means of Dr. Simroth’s pendulation theory.
That theory is founded on the supposed pendulation or shifting
of the poles in the course of time. As the South Pole gradu-
ally travelled northward, the present antarctic regions would
have slowly moved into more favourable climatic regions, and
have thus become habitable for such temperate animals and
plants as were able to reach them. When the Pole once more
moved back towards its present position, the antarctic fauna
and flora would again have endeavoured to regain suitable

climatic regions by any other land connections then available.

In this manner it is perfectly conceivable how, by a combina-
_ tion of serviceable land connections and a shifting Pole, the
present geographical distribution of the animals and plants
alluded to could have been brought about. We need not
imagine the former existence of a huge continent from which
long peninsulae projected, simultaneously joining all the
southern continents with one another. More slender land
bridges uniting one continent after another during succes-
sive geological ages with an antarctic land-mass would be
sufficient. Dr. Enderlein supposes that probably towards the
end of Cretaceous or in Hocene times the antarctic “‘ Heard-
‘Marion,”’ area was connected by land with Madagascar and
indirectly with South Africa. Tierra del Fuego extended
beyond the Falkland islands, South Georgia, South Orkneys
and Shetlands to Antarctica about the same time, and also,
perhaps during the Oligocene and Miocene Periods. Australia
was joined to the same area in Oligocene or Miocene times.
Dr. Enderlein,* on the other hand, believes New Zealand to
have been completely isolated from all other regions since the
Kocene Period.

The theory appears simple and plausible, and if it should be
proved that the Poles shift their position to the extent assumed
by Professor Simroth, it would explain the causes of some of
the great movements of animal life in a satisfactory manner.
Nevertheless, we cannot, as Dr. Enderlein acknowledges, dis-

* Enderlein, Giinther, “ Biologische Bedeutung der Antarktis,”
pp. 383— 350.

ee

PENDULATION THEORY age

3 pense with land connections, and he rejects the theories Of jn
ia accidental dispersal as quite inapplicable to the solution of the
: antarctic biological problems. For my own part, I think that
changes of land and water, combined with warm currents in
the Polar regions, would likewise explain the same phenomena
in a satisfactory manner, and I prefer to adopt the latter view
until we possess more definite information as. to evidence on
which the pendulation theory is founded. ~

I have endeavoured in this work to show how the gradual
evolution of our continents and the former changes of land
and water can be demonstrated by a study of the geographical
distribution of living animals and plants. Whenever possible
I have taken advantage of our palacontological and geological
knowledge in furtherance of this object, and I venture to
think that I have succeeded in unravelling some intricate
problems of the palaeogeography of America. Indirectly I
have thus been able to indicate the manner in which North
and South America became populated, and the extent to
which these continents took part in supplying animals and
plants to other regions of the world.

:

i]
i 3
14

FF 2

BIBLIOGRAPHY _

Principal Works consulted in the Preparation of this Volume

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Apams, C. C. “ Post-Glacial Origin and Migrations of the Life of
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Apams, ©. C. “The Post-Glacial Dispersal of the North American
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7 “7

INDEX

A

Acanthonyax petiverii, 333

Accidental distribution, of butterflies,
116, 117 ; ‘of snakes, 130 ; as ap-
plied to Bermuda, 192, 194; of
freshwater fishes, 232 ; in Antilles,
265 ; of animals and plants in Gala-
pagos islands, 300, 301, 306, 309

Achatellina, 308

Achatina achatina, 380

Achatinidae, 380, 390

Acodon brachyotis, 418

Actoniscus ellipticus, 190

ApaAMs, life in Alaska during
Glacial Epoch, 34, 35 ; southward
retreat of fauna and flora during
Ice Age, 35, 37, 38 ; centres of dis-
persal in south-east and south-west,
174 ; “biotic preserves,” 174

Adelopoma, 257, 273; stolli, 257 ;
martensi, 257

Aegialitis sanctae-helenae, 387

Aeglea laevis, 405

Aegleidae, 405

Aestrelata phaeopygia, 302

Agapeta, 350

Agarista, 214

Agassiz, A., subsidence of Bahamas,
185 ; origin of Galapagos islands, 296 ;
ocean floor off Panama, 332, 333;
relict fauna in Lake Titicaca, 361

Aaassiz, L., faunistic isolation of New
England, 56, 57

Aglossa, 377

Agonostomus, 290 ; monticola, 290

Agraulis, 179

Agrotis exclamationis, 214

Alaska, description of, 74, 75 ; Glacial
Epoch in, 76, 81; “black muck”
deposits, 79 ; fauna in Pleistocene,

78—81 ; mammalian fauna, 91, 92 ;
flora, 92, 93

Alberta, game preserves in, 119

Alces, americanus, 32; bedfordiae, 32;
machlis, 32 ; gigas, 92

ALCOOK, dispersal of Coeciliidae, 251

ALLEN, G. M., mammals of West
Indies, 282

ALLEN, J. A., species of reindeer, 5 ;
species of musk-ox, 7, 8;' polar origin,
of life, 23 ; Glacial Epoch, views
on, 34; Bering Strait land-bridge,
85 ; American mammalian types in
Asia, 85; opossums, 182; specific
distinctions of Solenodon, 282 ;
mammalia of Galapagos, 298, 299 ;
affinities of antarctic lands, 423

Alligator, 179, 180, 319; ‘mississip-
piensis, 179 ; sinensis, 180

Allorchestes dentatus, 361

Alsophis, 288

ALSTON, mammals of Central America,
248

Alytes, 204

Amalia, wide distribution of, 213, 214,
389 ; hewstoni, 213 ; gagates, 213 ;
ponsonbyi, 214 ; pectinata, 214

Amathusidae, 369

Amazon River, 363

Amblyopsidae, 164—166

Amblyopsis spelaeus, 165

Amblyrhiza, 267 ; inundata, 285

Amblyrhynchus, 302 ; cristatus, 304

Amblystoma, 136, 137 ; tigrinum, 136,
137; persimile, 137; jeffersonianum,
137

AMEGHINO, tree-porcupine in Santa
Cruz beds, 71; deer in upper Mio-
cene of Argentina, 109 ; affinities of
Phlaocyon, 151, 152; southern origin
of edentates, 244; South America

e@®™® American animals in Asia, 85, 86

472

as source of Tertiary mammalia,
244, 397 ; ancestral types of coypu,
283; Cuban cave man, 285; geologi-
cal history of South America, 341 ;
origin of American bears, 351; origin
of Viscaciidae, 353, 354; lemuroid
remains in Patagonia, 364, 365 ;
South Atlantic land-bridge, 365,
370, 371; sloth remains, 365;
opossum remains, 367; freshwater
deposits of Buenos Aires, 397 ; dis-
coveries of Tertiary fauna, 397, 398;
Amia calva, 163

ancestors of huanaco, 406

Ameiurus cantonensis, 89

Ameiva, 288

Amiidae, 163 x

Amphibians, in Hudson Bay region,
37 ; relationships of east American
and Asiatic, 135-137; relationship
of American and south European,
137, 138, 172; rarity of, in south-
western States, 204

Amphibulima, 271

Amphicyclotus, 257, 268

Amphipyra pyramidea, 214

Amphisbaena, 288, 375 ; ridleyi, 385

Amphisbaenidae, 173, 202, 288, 375

Amphiuma means, 172

Ampullaria, origin in Brazil, 362 ;
absent from Chile, 405

Anadenulus, 212

Anadenus, 213

Anarta, melanopa, 22, 36 ; leucocycla,
22; lapponica, 22

ANCEY, southern distribution of mol-
lusks explained by Antarctic con-
tinent, 423

Anchitherium, 148 —

ANDERSEN, geographical distribution
of bats, 299

Andes, flora related to that of Rocky
Mountains, 104

ANDREAE, Atlantic land-bridge in
Miocene times, 272 ; distribution of
Adelopoma, 257

ANDREWS, fossils of the Fayim in
Africa, 358, 373 ; land connection
between South America and north
Africa, 278, 373

INDEX

Androdon, 350

Anemone, origin and distribution of,
114 :

Anguidae, 202, 281, 347, 348

Anguis, 281

Anniella, 202

Anniellidae, 202

Anodons on Pacific slope of North
America, 162

Anodonta, marginata, 52 ; kennicotti,
52; pepiniana, 52

Anops, 376; kingi, 376; africanus, 376

Anosia archippus, 117

Antarctic continent, 419—426

Ants, in Bermuda, 189 ; in south-wes-
tern States, 215—217

Antilles, characteristics of fauna, 261;
geology and form of islands, 262,
264, 286 ; past geography as shown
by mollusks, 265—271 ; affinities of
fauna, 265—278; affinities explained
by land-bridge, 274; mammalian
fauna, 282—285; birds of, 289 ;
summary of geological development,
292—294 ; Bahamas, 288, 289;
Cuba, 261, 262, 285, 290, 291;
Jamaica, 284, 288 ; Portorico, 288

“ Antillean continent,’ 237, 241

Antilocapra americana, 112

Antilocarridae, 112, 113

Antlers of deer, development of, 108,
111, 112 ‘

Aphallarion, 212

Aplexa hypnorum, 72

Aplodontia, 228

Apocrypha, 413

“ Apollo ” butterflies, 90, 91

APPELL¢F, opposition to subsidence
theory of Farée Bank, 17, 18

Archaean land-mass in West Indian
region, 177

Arctia quenselti, 36 ; caja, 214

Arctoryctes, 246, 404

Arctotherium vetustus, 351

Arenicola marina, 16

Argentina, 395, 396 ; geological his-
tory of, 397 ; former climate, 401 ;
connections with North America,
402, 403 ; with Australia, 403, 404

Argynnis, 235, 413; chariclea, 22 ;
polaris, 22

ee

os

INDEX

ARLDT, connection between Asia and
North America, 97 ; Archaean rocks
on oceanic islands, 277; reptiles

and mollusks in Galapagos islands,

314; land-connection to Galapagos
islands, 316 ; parallelism of Pacific
islands, 327 ; former geographical
conditions of South America, 343,
344 ; on Atlantic land-bridge, 383 ;
connection between South America

. and Australian region, 425

Armadillo in Bridger deposits, 244 ;
in Santa Cruz beds, 399, 401; in
North America, 401

Armadillo (Isopod), 309

ARNOLD, climate of.
Period, 94—96

Arthrocomus, 413

Arvicola (see Microtus and Pitymys).

Ascaphus, 204 —

Ascension island, 396

Ashmunella, 206

ASHWORTH, distribution of marine
shore forms, 16 ; marine worms of
Patagonia and south Africa, 432

Asiatic types in America, 83—91,
earlier and later migrations, 317—
320 ; route of ancient Tertiary mi-
gration, 328, 329; antelopes in
America, 407

Astacus (see Potamobius).

Astrapotheria, 399

Atalapha (see Lasiurus).

Ateles vellerosus, 250

Athabasca - Mackenzie region, fauna
and flora of, 58—73

Atherina evermanni, 290

Atlantic islands, origin of, 383—393

Atlantic States, effect of moist cli-
mate on vegetation, 167

Atophyraxz, 201

Auckland island, earthworms of, 424

Austaut, Asiatic origin of Apollo
butterflies, 90

Avocettula, 367

* Axolotl,” 137

Pleistocene

B

Bahamas, raccoon in, 181; effect on
Gulf Stream by elevation of, 185
(See Antilles.)

473

BAILEY, distribution of Microtus, 28

BANGS, mammals of Labrador, 28 ;
water-vole of Florida, 182

BancGs and BRADLEE, Bermudan birds,
188

Banks, scorpions of Florida, 179

BARBOUR, on alligators, 180; Jamai-
can reptiles and amphibians, 288 ;
Bahama reptiles and amphibians, 288

BARRETT - HAMILTON, external cha-
racters of arctic hare, 9

BARRETT - HAMILTON and BONHOTE,
varieties of arctic fox, 11

Bartonius, 177

Bassaricyon, 249

Bassariscus, 201

Bates, antiquity of forests in South
America, 364; on Heliconiidae, 368;
discovery of Cryptostemma, 369

Baur, on Galapagos islands, 296; T7'ro-
gidurus, 311; harmonic and dishar-
monic faunas, 311—313; theory of
origin of Galapagos, 312 ;
accounts for. peculiarities of flora,
315 ; on Indo - Pacific continent,
323

Bear, black, 28 ; barren-ground, 61 ;
in Alaska, 80 ; spectacled, 350

Beavers, extinct in Alaska, 80; in
lower Pleistocene, 153

BEDDARD, connection between Pata-
gonia and the Australian region, 421

Beetles, distribution of running, 20 ;
in Scarboro’ Heights deposit, 43 ;
of Rocky Mountains, 117, 118; of
south - western States, 215; of Old
Calabar, 381; of St. Helena, 387

BELT, connection of Atlantic and
Pacific Oceans, 239 ; birds of Cen-
tral America, 250

BENHAM, faunistic affinities of New
Zealand, 424

BENTHAM, floral
Helena, 391

Berendtia, 206

Bermuda, 183, 184; geology of, 184,
186 ; comparison with Bahamas,
185; flora and fauna, 186—194; affi-
nities of fauna, 190 —

Berry, Pleistocene climate, 175 ; mid-
Cretaceous floral affinities, 414

affinities of St.

474

BIGELOW, Pacific medusae, 240;
absence of surface forms in parts
of Pacific, 335

Big-horn, Kamchatkan, 85, 104, 105;
Rocky Mountain, 104, 105

BINNEY, distribution of Helix hor-
tensis, 14

Birds, geographical distribution of,
.61; of Nova Scotia, 56; of
Mackenzie Region, 61; of Rocky
Mountains, 113; of Galapagos is-
lands, 801, 302; of Bermuda, 188,
189 ; of Central America, 250, 251;
of West Indies, 290; of South
America, 367—369

Bison, range and history of, 65—67 ;
in Gulf plains, 145

Bison, bison, 65; sivalensis, 66; alleni,
66, 80; scaphoceras, 66; crassi-
cornis, 67, 80; priscus, 67; occiden-
talis, 80

BLAISDELL, Tenebrionidae, 215

BLANFORD, permanence of ocean
basins, 277; on volcanic islands,
297 ; relationship of reptiles and
amphibians of South America and
Africa, 374, 376

Blanus, 375, 376

Blaps, 215

Blastocerus, 111

Blastomeryx, 110, 112

Blue-bird in Bermuda, 188

Boas, distribution of, 203

Boeckella, 424

BoETTGER, Tertiary Helices, 193;
Helicidae, affinities of, 206; on
Adelopoma, 257 ; Atlantic Miocene
land-bridge, 272 ; connection between
Galapagos and Central America, 313 ;
Clausilia of South America, 349 ; Ter-
tiary fossils in Amazon valley, 360

Boidae, 203

Boltenia, 272

Bombinator, 204

BONHOTE (see BARRETT-HAMILTON).

Boétherium, 154; bombifrons, 80, 154

Born, distribution of running beetles
in North America, 20

~ Bose and Touts, fossils of Isthmus

of Tehuantepec, 238; affinities of

Pacific and Atlantic faunas, 241

INDEX

BOULENGER, distribution of Lygosoma,
125 ; on Tropidonotus, 129 ; affini-
ties of Hmys, 134 ; distribution of
Coecilians, 370; distribution of Der-
mophis, 377 ; African fishes, 378, 379,

BOURGUIGNAT, identity of European
and American Clausilia, 272

BOUuvIER, distribution of Onychophora,
346, 369 ; distribution of Peripatus, 432

Bow-fin in Mississippi basin, 163

Brachionycha nubeculosa, 214

Brachydontes magellanica, 428

Brachylagus, 226

Brachylophus, 207

Brachymeles, 126

Brachypodella, 267

BRADLEE (see BANGS).

Bradypus, 366

Bradytherium in Madagascar, 366

BRANDEGEE, Californian flora, 208

BRANSFORD (see GILL).

BRAUER, arctic fauna, 6

Bray, plants common to Andes and
Rocky Mountains, 104; floral affi-
nities of North and South America,
415, 416

Brazil, 363; summary of geological
history, 393—394

BREHM, crustacea of Greenland, 19

BRENDEL, on Florida plants, 167

Bridger deposits of Wyoming,
143, 163, 229, 244

BRITTON, Flora of Antarctic con-
tinent, 422

BROOKE, structural characters’ of
Cervus canadensis, 68

Brooks, great range of climate in
Alaska, 74; geology of Alaska, 84

Brotulidae, 290

Brown, A. E. dispersal of reindeer,
5; North Atlantic land-connection,
25, 222; Rocky Mountain sheep,
104, 105 ; origin of Oreamnos, 106;
variation of garter-snakes, 128 ;
origin of rattle - snakes, 131;
centres of dispersal, 174

Brown, B., age of Potter Creek de-
posits, 29; Conard fissure, 61, 64,
70, 87 ; remains of mule-deer from
Conard fissure, 108; Symbos and
Scaphoceros, 155

102,

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INDEX

Brown, R., similarity of Greenland
and European reifideer, 4; arctic
hare, 9

Brown, R. N. R., on Diego Alvarez,
393

| «ee Brown, S., Bermudan flora, 187

Bruce, fossils from Falkland islands,
430; soundings in southern Atlantic,
433

Buckleyia, 256, 268

BupDE-LUND, on the Pacific Con-
tinent, 320

Budorcas, 106

Buffalo (see Bison).

Bufo, absence from Jamaica, 288

Bugs of St. Helena, 388, 390

Bulimus, 390

Bulimulidae, 269—271, 2738

Bulimulus, 176, 206 ; of Lower Cali-
fornia, 208 ; on ancient Pacific land,
209, 210; of Galapagos, 306—-308 ;
of St. Helena, 390; common to
Chile, Galapagos, and California,
410; forms not easily distinguish-
able, 269, 270; americanus, 270;
ridleyi, 270, 385

Bunting on Diego Alvarez, 293

Buprestidae, 425

BURCKHARDT, C.,
tinent, 427

BURCKHARDT, R., distribution of
flightless birds, 423

Burdwood Bank, 429

Butterflies, dispersal of, 115; of
south - western States, 214; of
Antilles, 289 ; of Florida, 179

on Pacific con-

: -C

Cactornis, 301

Caenolestes in Santa Cruz beds, 350,
404 ; in Ecuador, 350

California, geological history, 198—
200; Cape Region of, 199, 207;
fauna and flora of Cape Region, 207,
208 ; relationship with Europe, 211;
geology of Cape Region, 329, 330,
356 ; Cape Region a part of Pacific
land-belt, 331; animals common to
Chile, 333, 410, 412, 413

Californian islands flora, 210; pecu-
liar species of Hpiphragmophora,

475

410 ;
418

relicts of Pacific land-belt,

CALVERT, dragon - flies of Central

America, 258

Camarhynchus, 301

Cambaroides, 218—220

Cambarus, place of origin, 177, 178 ;
dispersal of, 218—220; primaevus,
220 ; cubensis, 291, 292 ; mewicanus,
291

Camel, ancient migrations, 86 ; fossil
in North America, 153 ; camel-like
animals of America, origin of, 406,
407

Camelidae, 86, 116, 406

Camelus, 153

CAMERANO, cranial differences in rein-
deer, 5; varieties of reindeer, 34

CAMPBELL (see HAYEs).

Campylaea, 206

Canadian forest region, fauna of, 63—
67

Cancer amphiaetus, 93, 94

Canidae, an ancient family, 149, 150

Canis, 149, 150; occidentalis albus,
61; latrans, 149, 430; dingo, 150;
antarcticus, 430, 150 ; tonggerana,
150

Capreolus, resemblance to American
deer, 111

Caprolagus, 225

Capromeryx, 113

Capromys, 282; columbianus, 283

Carabidae, 425

Caraboctonus, 349, 350

Carabus, supposed accidental distribu-
tion, 20; peculiar distribution in
North and South America, 235, 236,
412, 413 ; catenulatus, 20 ; nemo-
ralis, 20.

Carcharhinus nicaraguensis, 241

Carettochelyidae, 135

Careinocyon, 430

Cardiastethus, 391

Cardinal, in Bermuda, 188, 189

Cardinalis bermudianus, 189

Caribbean Sea, a gulf of the Pacific,
241, 332

Caribou, derivation of name, 38;
‘barren - ground,” 3, 5, 27, 58;
** wood-land,” 3, 5 ; ‘*‘ mountain,” 5

476

Carnivores, Cretaceous ancestors, 149

CARPENTER, Sonoran region, 196, 197;
Collembola from South Orkneys, 433

Carpodacus, 56

CARTHAUS, sea-water formerly more
salt, 276

Cascade Mountains, 103

Casmorynchus niveus, 362

Castor, extinct in Alaska, 80

Castoroides, 153, 285, 286

Cat-bird, in Bermuda, 188, 189

Cat-fish, 89, 361

Caton, likeness of wapiti and red-
deer, 68

Catostomus rostratus, 89

CAUDELL, on Phasmidae, 158

Cebidae, 364

Cebus, 364

Celestus, 281 —

Centetidae, 246, 282

Central America, faunal problems, 233,
234 ; geological features, 237, 238;
date of formation, 152; time of
submergence, 241, 242 ; elevated in
Pliocene Period, 243; flora and
fauna, 247—257; affinity with
Europe, 257; general affinities of,
259, 260

Centrurus, gracilis, 178 ; carolinianus,
178 ; margaritatus, 178 ; hentzi, 178

Cephalopterus ornatus, 362

Cegolis, 175, 176

Cercoleptes flavus, 151, 248, 249

Ceroglossus, 413

Certhia, 56

Certhidea, 315

Cervalces, 32

Cervidae, origin of, 109—111

Cervulus, 111

Cervus, origin of, 68 ; canadensis, 67
—69 ; distinct from American deer,
107, 108

CHAMBERLIN, T. C., and SALISBURY,
glaciation of Nova Scotia, 41;
interglacial phases, 45 ; ice disper-
sion from Keewatin centre, 46, 76,
77

CHAMBERLIN, R. V., North American
Lycosidae, 36

Chamops, 127

em CHAPMAN, origin cf Antillean fauna, 290

INDEX

Characinidae, 379, 380

Chauliodes, 289

Chelonians of north-eastern States, 134

Chelydridae, 134, 251, 319, 320

Chelydra, serpentina, 134 ; rosignonii,
135

Chile, 395; occurrence of northern
forms, 234 ; species in common with
California, 333, 334; poverty of
freshwater fauna, 405 ; distribution
of mammals, 406; species in
common with California and Gala-
pagos, 410 ; western extension of, 427

Chilean islands, 418

Chilonopsis, 390

CHILTON, Antarctic continent, 425

Chinchilla, 353, 354

Chipmunk, 63

Choanopoma, 176

Choloezus, 366

Chologaster, 165

Chondrogoma, 175

Choroghilus nigritus, 31

Chrosomus erythrogaster, 50

Chrysemys, 132

Chrysochloridae, 245, 246, 404

Chrysocyon, 430

Chrysothriz, 364

Chub, silver, in drift area, 51

Cichlidae, 234, 290, 362, 379

Cinclus, origin of, 113

Cinosternidae, 362

Cistudo, 134

Citellus, general range of, 60 ; parryi,
61, 85; douglasi, 61; tridecem-
lineatus, 61; busxtoni, 85 ; osgoodi,
92; nebulicola, 92; beringensis, 92;
barrowensis, 92; stonei, 92

Clausilia, range and _ geological his-
tory, 272, 273; discontinuous dis-
tribution of, 348, 349; pauli, 272,
349

Clemmys, guttata, 132 ; marmorata,
138, 222; leprosa, 133, 222; im-
sculgta, 133; morrisiae, 133

Coati, of western origin, 249

Cochlicopa lubrica, 72

COCKERELL, distribution of Helix hor-
tensis, 14 ; Florissant shales of Mio-
cene ge, 118 ; Florissant shales,
200 (See RosBINs.)

INDEX

Cocornis, 301

Cog, land-nemertean in Bermuda, 191

CoE and KUNKEL, Californian limbless
lizard, 202

Coecilians, 251, 252, 370

Coeciliidae, geological history, 251,
252, 348

Coendidae, 71

Coendu, migrations of, 70, 71; in
Brazil, 366 ; origin of, 403

Colias, in Rocky Mountains, 117 ; in
southern South America, 235 ;
nastes, 22

Coleoztera of South America related
to those of Australia, 425

Collembola from South Orkneys, 433

CoLEMAN, fossil plants as tests of

climate, 43; Canadian Pleistocene
flora, 44
Columbigallina. bermudiana, 188 ;

gasserina, 188

Conard Fissure, fauna of, 61, 64, 70,
107, 108, 153

Condylura cristata, 142

Conepatus, 201

Conolorhus, 304

Conoryctes, 244

Conulus, 306, 308 ; fabricii, 21

Conuropsis carolinensis, 159, 172

Conurus, 172

CONWENTZ, distribution of musk-ox, 7

Cook (see MATTHEW).

CookE, A. H., operculate land-mol-
lusks, 57

CooKE, W. W., bird migration, 168

CoopPeR, Californian mollusks, 208

CopE, varieties of bison, 66; Felis
hillianus, 107; distribution of
ground-lizard, 124 ; mud-puppy of
eastern States, 136; eastern and
western types of snakes, 173 ;
Sonoran region, 196; fossil voles,
224; fossils of Puerco formation,
244

COPELAND, flora of Trinidad, 396

Corals, fossil, of Barbados with
Mediterranean affinities, 278

Corydalis, 289

Cosoryx, 112

Cotingidae, 362, 368

Cougar, vast range of, 106, 107

ATT

CoviLLE, land-bridge between Asia and
North America, 83

Coyote, distribution in North America,
149, 150; related to Falkland
Island wolf, 430, 431

Coypu, distribution and ancestry, 282,
283, 396

Crabs, distribution of freshwater, 255;
of Cuba, 291; of coast of Chile,
333 ; of southern South America, 405

CraGin, fossil species of MNemor-
rhaedus, 106

Crayfish, freshwater, distribution of,
217, 218 ; of south-western States,
218 ; of Cuba, 291; of South
America, 405 ; of Chile and New
Zealand, 420, 424, 426

CREDNER, fauna of relict lakes, 49

Creodonta, 373

Crepidula gregaria, 428

Crocidopoma, in Antilles, 256, 268

Crocodilus americanus, 180, 181

Crotalus, 131, 253; horridus,
terrificus, 131, 253

Crow in Bermuda, 188 *"

Crustacea, of the Great Lakes, 48, 49 ;
blind, of Cuba, 291

Cryptostemma westermanni, 369, 370,
382

Cryrtobranchus, 83 ;
135 ; japonicus, 135

Ctenodactilus, 372

Ctenodactylidae, 371

Ctenomys, brasiliensis, 371 ;
371

Ctenosaura hemilopha, 207

Ctenucha, 214

Cuba, poverty of mammalian fauna,
261, 262; cave fauna, 285, 290 ;
fishes, 290, 291

Cubaris, pisum, 179 ;
309

Cucullaea alta, 428

Cupiennius sallei, 178

Curassows in Central America, 250

Curculionidae, 391

Cyclophis, 130, 319; aestivus, 130

Cyclophoridae, 256, 257, 268

Cyclura, 207

Cylindrellidae (see trobobtteine).

Cynomys, 148, 149; ludovicianus, 148

131 ;

allegheniensis,

minutus,

galapagoensis,

~~
K

478

Cyprinids, 50
Cyrtotoma, 256, 268
Cystognathidae, 421

D

Dace, red-bellied, in drift area, 50

DaHL, distribution of spiders, 191 ;
arctic centre of dispersal, 427, 428 ~

Dau, Helix hortensis in Pleistocene
clays, 14; temperature of Pliocene
seas, 16; land between Asia and
North America, 83 ; fauna of north-
east Pacific, 93; subsidence in
Alaska in Pleistocene times, 96;

marine gravels at Nome, 94;
climate during Tertiary Era,
94—97 ; on .Helicina, 158; geo-
logical history of Florida, 176 ;

mollusks of Florida, 176; Califor-
nian Bulimulus, 208; Galapagos
islands, 296; importance of acci-
dental distribution, 306, 307;
Alaskan leaf-bed, 318, 319; Miocene
mollusks of Penjinsk, 319; marine
faunal provinces, 333, 334

DALL and Harris, Miocene change of
Gulf Stream, 186

Day, geology of Labrador, 41

Damon variegatus, 382

Damophila, 350

Darien, isthmus
America).

Darwin, Galapagos islands, 295—297 ;
human importations, 298 ; birds and
lizards of Galapagos, 301—303; flora
of Galapagos, 310; subsidence of
Pacific Ocean, 321, 322, 331 ; Ascen-
sion island, 386; description of
Falkland islands, 430, 431

Dasychira roseti, 36

Dasypoda, 399, 401

Dasyuridae, 183

Dawson, G., foraminifera in Glacial
clays, 47

Dawson, J. W., Pleistocene flora and
fauna of Canada, 44, 53 ; foramini-
fera in Canadian Pleistocene clays,
47 ; views on Glacial Epoch, 98

Davip, atoll boring at Funafuti, 321

Deer, origin of, 109—111

of (see Central

INDEX

DENBURGH, VAN, lizards of Lower Cali-
fornia, 207 ; reptiles of Galapagos,
305 ; reptiles and amphibia of Cali-
fornian islands, 418

Dendrobatidae, 377

DEPERET, pedigree of horse, 147;
original home of fossil horses, 148;
centres of origin, 227 ; Miocene and
Pliocene migrations, 230 ; age of
Central America, 243

Dermatemydidae, 236, 251

Dermatemys mawi, 251

Dermophis, 370, 376

DE SE.ys, Pitymys from St. Gothard,
223

Devisia mythodes, 135

Diapheromera femorata, 158

Dibelodon, 231

DICKERSON, amphibians of Hudson
Bay region, 31

Dicrocerus, 111

Dicrostonyx, torquatus, 9—11 ;
sonius, 11, 27, 60

Didelphyidae, 229, 367, 403

Didelphys, 182, 183 ; marsupialis, 182,
283, 366

DIEDERICH, distribution of magpies, 88

Diego Alvarez island, 393

Die, anatomy of manatees, 279, 280

Dinosaurs, 400

Dione, 179

Diplocardia, 174

Dizlocynodon, 180

Diplodon, 425, 426

Diploglossus (see Celestus).

Diplommatininae, 257

Dipodomys, 201

Dippers, distribution of, 113

Discoglossidae, 204

Discoglossus, 204

DitM4Rs, Sceloporus undulatus, 126 ;
remarks on rattle-snakes, 131; re-
marks on terrapins, 132 ; habits of
snapping turtles, 134

DonGE, description of bison herd, 65

Dog, wild, of Australia, 150 ; of Java,
150

Dolichonyx oryzivorus, 301

Dolichotis, 408

D’OrzicNY, mid-Atlantic land-bridge,
359

hud-

i
d
P

INDEX

Dragon - flies of Florida, 178; of
Central America, 258; of Antilles,
289 fret

DRASCHE, boundaries of Pacific, 328

Drift-deposit in North America, 40—
43; absence of, in Labrador, 41

Dromicus, biserialis, 304; chamissonis,
304

DRYGALSEI, V., coast lands in Green-
land never glaciated, 18

Drymaeus, 175 ; dominicus, 176, 270;
dormani, 270

EARLE, tapiroids
America, 353

Earthworms, in Florida, 174 ; affinity
of North and South American, 412;
importance of, in zoogeography, 423,
424; of Falkland islands, 431

Echimyinae, 372

Echinoids, fossil of America and
Europe, 278

ECKEL and PAULMIER, reptiles of New
York, 123, 127

Ecuador, an ancient land-mass, 350 ;
fauna of, 354

Edentates, range of, 152, 153, 156;
origin of, 244, 245; in Santa Cruz
beds, 399

Eglandina, 175

EIGENMANN, on blind fishes,165; fresh-
water fishes of Central America,
253 ; affinities of Cuban fishes, 291;
geological history of South America,
340; Orestias, 362; land-bridge be-
tween Africa and South America,
379 ; Patagonian fishes, 405

Eisen, Cape Region of Lower Cali-
fornia, 330

Elateridae, 425

Eleodes, 118

Elodinae, 215

Elephants, remains on Pribilof islands,
78 ; fossil in North America, 153,
200, 230, 231, 358, 359

Elephas, primigenius, 80; columbi, 83,

in Europe and

479

87, 153; antiquus, 87; meridionalis,
87 ; imperator, 87, 153
EwuiotT, black musk-ox, 7

- EMERSON, Texas subterranean newt,

136

EMERTON, affinity between spiders of
America and Europe, 23

EMERY, honey ants, 216 ; Formica in
America, 216

Emydidae, 134 -

Emys, distribution of, 51, 132—134;
blandingi, 51, 182; orbicularis, 51

Enallagma, 178

ENDERLEIN, insects of south Polar
regions, 433, 434 ; former antarctic
land-connection, 435

Endodonta, 306, 308, 390;
308

ENGELHARDT, fossil plants of Chile,
414, 415

ENGLER, affinities of flora of Asia and
North America, 93 ; plants common
to Andes and Rocky Mountains,
104 ; affinities of western Ameri-
can plants, 139, 140 ; origin of
Florida plants, 168; land-bridge
between South America and Africa,
383 ; St. Helena flora, 392 ; Tristan
da Cunha flora, 393; floral affini-
ties of North and South America,
415

Entelops, 366

Eohippus, 147, 228

Epanorthidae, 350, 404

Epihippus, 147

Epilobocera, 255, 291

Epiphragmophora, 206, 212,
tucumanensis, 411

Erebia, 117

Erethizon, 71, 366, 403 ; dorsatus, 27,
69; epixanthum, 70

Eryx, 203

Eublepharus, 347

Euceratherium, 154

Euchirotes, 207 ; biporus, 202, 203

Euconulus fulvus, 72

Eugenia, 350

Eumeces, 123—126 ; quinquelineatus,
123, 189; latiscutatus, 189; longiros-
tris, 189

Eurymetopum, 413

helleri,

410 ;

480

Eustephanus fernandensis, 418

Eutenia sirtalis, 127

Eutoxeres, 350

EVERMANN (see JORDAN).

Evotomys, 29 ; ungava, 27 ; proteus,
27; wrangeli, 92; dawsoni, 92;
orca, 92

F

Falkland islands, geology of, 429, 430 ;
fauna and flora, 431

Farée Bank, shells dredged off, 17

Faxon, crayfish, 218, 220

Faxonius, 177

Felis, concolor, 107 ; hillianus, 107

Fernando de Noronha, 384, 385

FERRIS, mollusca of south - western
States, 206

Fiber, obscurus, 56, 64; zibethicus, 64,
92 ; spathulatus, 64, 92 ; annectens,
64.

FEILDEN and DE RANCcE, banded lem-
ming in Greenland, 11; glacio-
marine deposits, 47

Florida, flora of, 167; relation to
Antilles, 168; former geological
conditions, 168—172 ; fauna of, 175
—182 ; majority of faunal elements
non-tropical, 181, 182; course of
Gulf Stream across, 185

Florissant Shales, insects and plants
of, 118, 200

Flying squirrel, distribution of, 63

Foraminifera, in boulder clay, 41

Forses, relationship of Madagascar
and South America, 375 ; Antarctic
continent, 421

Forest region of North America, fauna
of, 31, 63

Formica, cineria, 216 ; rufibarbis, 216

Fox, arctic, 11, 27; red, 27; New-
foundland, 56

FRaAzeR, Archaean land mass in Carib-
bean Sea, 177

Frogs, near Hudson Bay, 31; Florida
tree, 173 ; in South America, 377

Funafuti, boring coral reef at, 321,
322

FuRLONG, Huceratherium
fornian cave, 154

in Cali-

INDEX

G

GaDow, affinities between reptiles of
Madagascar and America, 126 ; dis-
tribution of salamanders, 137, 138 ;
distribution of Scaphiopus, 205 ; age
of genus Spelerpes, 221; home of
Coeciliidae, 251, 252; geological
history of Antilles and Central
America, 287 ; origin of Galapagos
tortoises, 313; on Dendrobatidae,
377

Gaeotis, 271

Galapagos islands, origin of fauna and
flora, 295—317

Galaxiidae, 421

Galeoscoptes bermudianus, 189

Gallinula galeata, 188

Gallinule, Florida,
Alvarez, 393

Ganodonta, 244

Ganoid fishes, of Mississippi, 88, 89,
163, 164

GARDINER, beetles of White Moun-
tains, 37

GARMAN, H., on blind fishes, 165

GARMAN, S., Bermudan skink, 189 ;
reptilian fauna of Galapagos, 303

Garnieria, 273

Gastrodonta, 193 -

GAUDRY, affinity of Patagonian extinct
fauna with that of New Mexico and
France, 402

Gecko in Galapagos islands, 303

Geckonidae, 303, 304

GEIKIE, A., on permanence of ocean
basins, 274, 276

GEIKIE, J., Greenland in Ice Age, 18 ;
inter-glacial phases, 45; gigantic
glaciers in Ice Age, 69

Geoemyda punctularia, 347

Geomalacus, 213

Geonemertes agricola, 191

Geospiza, 315

GIDLEY, Pleistocene species of Hqguus,
146, 147; on fossil raccoon, 152

“* Gila-monster,” 201

GILL, distribution of mud-minnows,
51; land-bridge between Asia and
America, 83, 88; fishes, as indicators
of changes of land and water, 377,

188 ; on Diego

INDEX

378 ; southern continental land con-
nections, 420, 423

GILL and BRANSFORD,
Nicaragua, 240

GILMORE, Pleistocene
Alaska, 79, 80

GIRARD, moths common to Canada and
Europe, 22

Glacial Epoch, survival of life in
Greenland during, 18—25;. elevation
of land in, 14, 42, 98 ; cause of, 15,
99, 318; mild climate in northern
latitudes, 19, 24, 43—46, 81, 154—
157; effects of, on animals and
plants, 37—-45 ; survival of species
in drift area, 36, 40, 41, 52; in
Newfoundland, 41, 55; in Nova
Scotia, 56; not caused by diminu-
tion of temperature, 76, 156; in
Alaska, 76—79, 81; in Siberia, 81,
82 ; its influence on fauna and flora,
175 ; inter-glacial epochs, 45

Glandina, fossil in Florida, 171; in
Europe, 271, 272

Glaresis, 215

Glauconia, dulcis, 203 ; humilis, 203

Glauconiidae, 203

Glutton in Labrador, 27

Glyptodontia, 399

Glyptotheriwm, 153

Gnathocerus masxillosus, 215

Goat-antelopes, 106 |

Goat, Rocky Mountain, 104—106

GODMAN and SALVIN, researches on the
fauna and flora of Central America,
246 ; Central American insects, 258

Gonatodes, 304

GoopRIcH, on Ceratodidae, 379

Gophers, distribution of, 60

Gough island (see Diego Alvarez).

GOULD, Pacific continent, 321

GRABAU, geological history of Great
Lakes, 54, 55

Grandala, 188

GRANDIDIER, on Bradytherium, 366

GRANGER, on Eocene horses, 147

GRANT, varieties of reindeer, 3 ; nor-
thern land-connections, 25 ; range
of moose, 32 ; Rocky Mountain goat,
105

Gravigrada, 244, 399

L ate

deposits in

fishes of ;

481

GRAY, affinities of flora of Asia and
America, 92, 139 ; Rocky Mountain
flora, 103 ; North and South Ameri-
can plants, 415

GREENE, flora of Californian islands,
210, 329

Greenland, flora and fauna, 3—22;
land-connections, 12, 13, 30; sur-
vival of species in Pleistocene times,
18—21; former climate, 19; affini-
ties with Labrador, 42

GREENMAN (see ROBINSON).

GREGORY, elevation of Florida, 170 ;~
junction of Atlantic and Pacific,
239, 241, 242; land - connection
between North and South America,
264 ; abysmal deposits in Barbados
and Cuba, 277; on fossil sea-
urchins, 278 ; on fossil corals, 278

GRENFELL, description of Labrador, 27

GROTE, noctuids common to Europe
and North America, 22; effect of
Glacial Epoch on range of butter-
flies, 38, 39 _

Ground-dove, in Bermuda, 188

Gryllus bermudensis, 189

Grypotherium Listai, 400

Guadalupe, flora of, 417

Guatemala, flora of, 247 ~

Guestieria, 348

Guiana, as centre of dispersal, 362

‘Gulf Plains,” 144

Gulf Stream, course in Tertiary times,
185, 186

GuLICK, Bermudan fossil mollusca, 193

Gulo luscus, 27, 61

GuNTHER, Central American fishes,
240 ; reptilian fauna of Galapagos,
303 ; land isopod from Galapagos,
809 ; distribution of fishes, 378 ;
fauna of Ascension, 386

Guppy, H. B., on Pacific continent,
324—326 ; mangrove formation, 333

Guppy, R. J. L., mid-Atlantic land-
bridge, 278

Gymnocephalus calvus, 362

H

HAACKE, Polar origin of life, 23, 428
HACKEL, affinities of North and South
American floras, 415, 417
II

482

Hadruroides, 349, 350

Hadrurus, 349, 350

Halichoerus, 280

HanpuirscoH, on fossil insects, 118,
158, 391 ; fossil Liometopum, 216

HANSEN, distribution of Koenenia, 217

Hapalidae, 364

Haplarmadillo, 190

Haplophora, 258

Hare, range of, 224—226 ; arctic, 9,
10; fossil of England, 10; Irish,
10 ; in Mackenzie Region, 59; Cape
jumping, 372, 373 ; Patagonian, 396

Harris (see DALL).

Harrison, Mackenzie River, 58

HARSHBERGER, effects of Glacial Epoch
on flora, 39, 40; flora of Florida,
168, 169 ; Bermudan flora, 187

HARTERT, on humming-birds, 350, 367

HARTERT (see ROTHSCHILD).

HatcHER, on American palaeontology,
102

Have, on Pacific continent, 327 ~

Hay, origin of fossil turtles, 133, 134,
251; climate of Pleistocene Period,
154—156

Hayes and CAMPBELL, change of river
courses, 162, 163

HEBARD (see REHN).

‘ HEDLEY, north Atlantic land-connec-

tion, 30; Placostylus, 209 ; Pacific
land - connections, 323, 324; ant-
arctic land-connection, 421, 422
HEILPRIN, origin and migration of
animals, 97 ; Bermuda islands, 186;
Antarctic continent, 422
Helicidae, 193, 205, 212
Helicigona, 212, 411

Helicina, 192, 306, 308 ; chrysocheila, .

157 ;. orbicula, 157; occulta, 157,
158 ; convewxa, 192, 193

Heliconiidae, 368

Heliconius, 179; charitonia, 368

Helix, hortensis, distribution of, 13,
14, 39, 141 ; in Labrador, 30; in
Pleistocene clay of Maine, 39 ; im-
bricata, 193

** Hell-bender,” 135, 319

HELLER, mammalia of Galapagos, 299;
reptiles of Galapagos, 303, 304 ;
geological age of Galapagos, 305

INDEX

HELLER (see SNODGRASS).

Heloderma, 202

Hemiauchenia, 406

Hemiptera, common to Europe and
America, 89, 90 ; of St. Helena, 388

Hemphillia, 212

HEMSLEY, Bermudan flora, 187 ; Cen-
tral American and Mexican floras,
246—248 ; on origin of Galapagos
islands, 315

Heros, tetracanthus, 290 ; nigricans, 290

Herpele, 370

HERSHEY, ancient
Panama, 331

Hesperarion, 212

Hesperomys, 298

Hexura, 412

HILL, orogenic movement in Antilles,
171; geology of Panama, 236—238;
east coast of America in pre-Cre-
taceous times, 263, 264; sunken
land west of Central America, 331

HINTON, origin of arctic hare, 10

Hipparion, 148

Hoatzin, 362

Hodomys, 201

Ho.puavs, on Pacific continent, 324

HOLLIcK, east American flora, 140, 141

HOLLISTER, on musk-rats, 64

Holoszira, 206

Homalota, 391

Homo cubensis, 285

Homunculidae, 365

HOooKER, survival of plants in Green-
land, 17; Rocky Mountain flora,
108 ; Asiatic floral element in North
America, 139 ; floral affinities of St.
Helena, 391 ; former antarctic land-
connections, 420

Hornabay, extermination of bison, 65;
habits of Rocky Mountain sheep, 105

‘** Horned-toad,” great antiquity of,
202

Horses in America, extinction of, 146;
geological history, 146, 148, 228

HorvaTtH, Hemiptera common to
Europe and North America, 89, 90

HOWARD, spread of species by agency
of man, 65

HoworrH, level of land in Pleistocene
times, 15; temperate climate in

land west of

ae baie om

INDEX

Arctic regions, 19; mild climate

during Glacial Epoch, 46; Forami-—

nifera in glacial clays, 47; water as
agent in formation of glacial de-
posits, 77 ; past climate of Siberia,
81; range of mammoth, 86

Hoy, on Mysis relicta in Lake
Michigan, 48

Huanaco, distribution of, 406

Hopson, on pampas of Argentina, 396,
397

Hudson Bay region, 31—36 ; invaded
by waters of Arctic Ocean, 47

HULL, pre-Glacial elevation of land,
‘14

Humboldt Current, striking Galapagos
islands, 294, 300; did not exist
during Tertiary Era, 334, 335

Humming-birds, range of, 250, 367,
368

KC Hutia in Antilles, 282

Hutton, on Pacific land-connections,
322, 420, 426

HUXLEY, on cray-fish, 218

Hyalinia, radiatula, 72; nitidula, 72;
cellaria, 389 ; alliaria, 389

Hyalinia (see Vitrea).

Hyla gratiosa, 173

Hymenochirus, 377

Hymenoptera, wingless of Australia
and South America, 433

Hyracotherium, 147

Hystricidae, 71

. Hystricomorpha, 371—373 ; in Santa

Cruz beds, 399, 402

Iguanavus, 127

Iguanidae, 126, 202, 207, 304, 305

IHERING, V., affinities of Phlaocyon,
151, 152; origin of Procyonidae,
152; dispersal of mollusks, 161 ;.
on Mutelidae, 161 ; range of
Helicidae, 205, 206, 212; distribution
of Unionidae, 254; Archhelenis, 274;
on origin of Galapagos islands,
313 ; Pacific Continent, 322 ; fossil
marine mollusks of South America,
334 ; researches in South America,

483

337 ; freshwater mussels of Brazil
and Africa, 338 ; palaeogeography
of South America, 339, 340; dis-
tribution of Clausilia, 349; origin
of South American bear, 351 ; South
America in Eocene Period, 362';

land-connection between Africa ae ¥ —_

America, 380; flora of South
America, 383; Fernando de
Noronha, 385 ; flora of St. Helena,
392 ; dispersal of wolves, 396 ; dis-
tribution of freshwater mussels in
South America, 405; on age of
Santa Cruz beds, 398 ; relationship
of west American and European
shells, 411; faunistic affinities of
Chile and New Zealand, 420, 421 ;
dispersal of marine mollusks, 428,
429; affinities of Falkland island
wolf, 430

Insectivora, of eastern States, 141,
142 ; of Bridger deposits, 143; of
south-western States, 201; of Santa
Cruz, 399

Insects from Antarctic regions, 433,
434

Ionolaema, 350

Ischyromidae, 228

Isectolophus, 353

Isometrus maculatus, 389

J

JACOBI, connection between Australia
and South America, 421

Japyx, 411; solifugus, 411; subter-
raneus, 412 ; saussurei, 412

JOHANSEN, subsidence of land tested
by marine shells, 17

JOHNSON, distribution of Helix hor-
tensis, 14

JOLY, on permanence of ocean basins,
275, 276

JONES, submarine deposits in Ber-
muda, 184

JORDAN and EVERMANN, origin of
North American blind fishes, 165

JORDAN, Central American fishes, 240

Juan Fernandez island, 418

112

484
K

Kangaroo-rats of western States, 201

Karscu, on Cryptostemma, 370 ; dis-
tribution of Japya, 412

Katzer, geology of South America,
342—344, 360

Keewatin ice-sheet, 73, 77

KENNARD and WoopwarRb, post-Plio-
cene mollusca, 21

Kerria, 208, 412

Kessleria, 88

Kingsleya, 255

Kinkajou in Mexico, 248

Kwnopr, land-connections between Asia
and North America, 84, 319

Koenenia, 412 ; draco, 217 ; mirabilis,
217 ; wheeleri, 217

KoKEN, geology of South America, 343

KOoLBE, distribution of Hnallagma,
179 ; distribution of beetles, 215 ;
Antillean dragon-flies, 289 ; South
Atlantic land-bridge, 381 ; antarctic
land-connection as shown by beetles,
425, 432

KOBELT, Helicidae, 206 ; distribution
of Cyclophoridae, 257, 268 ; affini-
ties of European and Antillean mol-
luscan faunas, 271; zoogeograpby
of St. Helena, 389

KowWARZIK, structure of musk-ox, 7,
8; musk-ox of Mackenzie region,
59 ; the genus Ovibos, 154

KRAEPELIN, Scolopendridae from Cali-
fornia and southern Europe, 217 ;
distribution of Damon variegatus,
382

KRiIsHTAFOVITOH, North Atlantic land-
connections, 25

KUNKEL (see COB).

‘* Kuroshiwo ” current, 94, 95, 318

L

Labrador, 26, 27; flora and fauna,
26—31 ; connection with Greenland,
30 ; affinities with White Mountains,

42

Lachesis, 131

I

‘

INDEX

Lagopus, 62; albus,
62; Jleucurus, 62; scoticus, 62;
mutus, 62 ; hyperboreus, 62

Lagidium, 353

Lagomorrha, 224—226

Lagostomidae (see Viscaciidae).

Lakes, Great, of North America, in-
vaded by the sea, 47 ; fauna of, 49,
50; geological history of, 50, 54

Sane huanachus, 406

LAMPLUGH, on inter-glacial epochs, 4

Lampsilis, 254; borealis, 52 ;
superiorensis, 52

Land-connection, north Atlantic (be-
tween Scotland, Greenland, and
Labrador), 12—25, 30; mid-Atlan-
tic (between southern Europe and
West Indies), 203, 271—281, 293,
294, 309; mid-Atlantic (between
southern Europe and. south-western
North America), 110, 114, 120, 164,
173, 203, 204, 211—230, 366—380 ;
south Atlantic (between eastern
South America and west Africa),
110, 282, 338—340, 366—385, 389,
390, 392, 394; south Atlantic (be-
tween Patagonia, South Africa, and
Madagascar), 344, 372, 375, 404, 405,
429—433 ; north Pacific (Bering
Strait), 5, 12, 28, 29, 32, 61—71, 62
—97, 115; north Pacific (between
western North America and eastern
Asia), 202, 318—329, 407, 408;
Pacific belt (between North and
South America westward of Central
America), 71, 245, 246, 254, 316, 317,
329—335, 347, 356—358, 401—403,
408—418, 431; Antarctic (between
Patagonia and Chile, and Australia
and New Zealand) 839—342, 403,
404, 419—429, 433—435; Atlantic
(between Bermuda and West
Indies), 183, 205

Land-nemertean in Bermuda, 191

LANKESTER, on extinct animals, 400

LAPPARENT, geology of South America,
342

Lasiurus, 299;
semotus, 300

LECHE, origin and age of Centetidae,
282

62; rupestris,

brachyotis, 299 ;

ne ee ee ee

_

“2° a ee ee eee |

INDEX

LEcoQ, glaciers produced by high tem-
perature, 45

Leipy, American palaeontology, 102.

Lemming, arctic, 9, 11 ; in Mackenzie
region, 60

Lemming-voles, 15; range of, 28

Lemmus, 60; trimucronatus, 60;
minusculus, 60, 92; nigripes, 60,
92; lemmus, 60

Leonia, 272 ;

Lepidoptera of Greenland, 22; of
White Mountains, 36; of Alaska, 90,
91; of Rocky Mountains, 115; of
Antilles, 289

Lezidosiren, 378

Lepidosirenidae, 378, .379

Lepidosteus, 163, 164, 290; osseus,
163, 164; tropicus, 164; tristoechus,
290 .

Leporidae, 224—226

Leptinaria (see Tornatellina).

Lerptomeryx, 110

Leptotherium, 113

Leztotrichus granulatus, 190

Lepus, 225, 226 ; variabilis, 9 ; bangsi,
56 ; othis, 92 ; poadromus, 92

Lerma River, fish fauna of, 232

Letourneuxia, 213

Lichanura, 203 ; trivirgata, 203, 207

Liguus, 175 ; fasciatus, 176

Limnaea, vahli, 21; holbolli, 21;
palustris, 2; stagnalis, 72; trun-
catula, 72

Limnolagus, 225, 226

Limnophylidae, 413

Linopodes, 258

Liometopum, 216 ; apiculatum, 216 ;
microcephalum, 216 ; lindgreeni, 216

Liogpelma, 204

Lioreltis vernalis, 130

Liparis, 307

Lithobius, provocator, 189 ;
densis, 189

Litopterna, 399

Littorina littorea, 16

Lizards, scarcity of, in eastern States,
123 ; abundance in western States,
196 ; Bermudan, 189 ; in California,
207; in Galapagos, 302—304 ; in
South America, 369; blue-tailed,
123, 125; burrowing, 202, 203;

bermu-

485

swift, 123 ; ground, 124; limbless,
202

Llama, 406 0%

Losey, north Atlantic land-connec-
tion, 25

LocarD, on Clausilia, 272

LONNBERG, structure of reindeer, 4

Lorhiodontidae, 353

Lovén, marine relicts in freshwater
lakes, 48

Loxia, 56

Loxocemus bicolor, 320

| Loxomylus, 267

Lucdnidae, 425 e

Lucas, fossil bisons of North America,
66; land-connection, Asia and North
America, 83 ; fossil sheep in Ni-
caragua, 105

Lucifuga subterraneus, 290

Lumbricus castaneus, 39

Lutra degener, 56

_ Lychas maculatus (see Isometrus).

Lyciscus, 430

LYDEKKER, varieties of reindeer, 3, 4 ;
musk-ox from Greenland, 7 ; extinct
bison, 67; relationship of wapiti
to Siberian maral, 68; origin ‘of
American deer, 109, 110; age of
Falkland islands, 151; origin of.

‘ opossums, 183, 367 ; origin of Cen-
tral America, 243; affinity be-
tween African and American faunas,
371 ; Falkland island wolf, 430

Lygosoma laterale, 124, 125, 319, 320

Lynx subsolanus, 56

LYON, on hares and their allies, 225 -

M

Mabuia, 376 ; punctata, 376, 385

MACFARLANE, mammals of north-west,
58

Mackenzie River, 58

Macroclemmys temminckii, 135

Macrorteryx, 368

Macrorharhis, 390

Macrorhinus leoninus, 428

Macquarie islands, éarthworms of, 424

MavDDREN, life in Alaska during Pleis-
tocene times, 78, 79

486

Magellan flora, affinities of, 417, 418

Magpies, distribution, 87, 88

Masor, ForsytH, meadow-voles, 224 ;
on Lagomorpha, 224; on fossil
Leroridae, 225, 226 :

Malacoclemmys centrata, 132

Mammoth in Alaska, 78—80, 87; in
Siberia, 82

Manatees on both sides of Atlantic,
279, 280

Manculus, 172

Manidae, 373

Manis, 372

Mantisza, 289

Maral deer, 68

Margaritana margaritifer, distribution
of, 34, 87, 51, 52, 55; on Pacific
slope of North America, 162

Marmoset, 364

MarsH, fossil bison, 66 ;
of Cervidae, 110

Marsupials, geological history of, 182,
183, 366; affinities of Patagonian,
403

Marten in Newfoundland, 56

progenitors

MARTENS, mollusca of Central
America, 256

Marx, Bermudan spiders, 191

Massoutiera, 372

Mastodon, 70, 87, 1538, 358; advent
in America, 408, 409 ; americanus,

80 ; chilensis, 408 ; bolivianus, 408;
andium, 408

MATTHEW, land-connection between
Asia and North America, 84; an-
cestry of Odocoileus, 110 ; insecti-
vores of middle Eocene, 143;
Eocene and Miocene carnivora, 149
—151; junction of Florida and
Cuba, 171; Lagomorpha, 226 ;
fossil rodents, 228; Agternodus,
246 ; fossil edentate in Cuba, 285 ;
Mascall beds of Oregon, 358

MATTHEW and Cook, antelope remains
in Nebraska, 407

McLAcHLAN, distribution, of Limnophi-
lidae, 413

Mecicobothriidae, 412

MEEK, Lerma River fishes, 232;
Nicaraguan fishes, 240

Megalobatrachus, 135

INDEX

Megalocnus, 293

Megalomastoma, 269

Megalomys (see Moschophoromys).

Megalonyx, 70, 87; in Miocene of
North America, 152, 153 ; in drift
area, 156; in Pliocene of Texas,
235 ; in Oregon, 358

Megarhaphis, 388, 390

Megascolecidae, 412

Megatherium in Patagonia, 400

Meleagris, galloparo, 159

Meridogastra, 370

Meristhus scrobinula, 321

MERRIAM, C. H., on Synagtomys, 28 ;
destruction of life in Glacial Epoch,
34; prairie fauna, 148, 149; fauna
of southern Florida, 175; Sonoran
region, 196, 197

MERRIAM, J. C., Asiatic antelopes in
America, 407

MERRILL, on Lower California, 207

Merycodontinae, 112

Merycodus, 112

Mesohippus, 147

Mesolama, 406

Metacanthus concolor, 391

Metacheiromys, 401

Metoponorthus sexfasciatus, 190

Mexico, eastern, relationship of fauna,
198 ; geological history, 199, 200;
relicts in west, 232 ; flora of south,
247

Miacidae, 149—151

MICHAELSEN, distribution of earth-
worms, 431

Microbiotherium, 403

Microphrys platysoma, 333

Microsauri, 304

Microtus, range of, 28—64 ;
27, 28; pennsylvanicus,
terraenovae, 56; operarius, 92;
unalascensis, 92; kadiacensis, 92 ;
yakutatensis, 92 ; sitkensis, 92; in-
nuitus, 92 ; abbreviatus, 92 ; alleni,
182

Milax (see Amalia).

MILLER, mammals of White Moun-
tains, 87 ; meadow-voles, 224

MILNE-EDWARDS, on antarctic pro-
blem, 423

Miohippus, 147

enixus,
27, 28;

INDEX 487

Miolania, 404

Mississippi, fishes of, 88, 89, 163;
drainage area, 144; description of
its course, 160 ,

Mites of Central America, 258

Moeritherium, 358

Mole, 142; star-nosed, 142 ; fossil,
143; golden, 245, 246, 404

Mole-mice, 201

Mole-shrew, 201

Mollusks, land and freshwater, in
Hudson Bay Region, 37; slow dis-
persal, 52; as illustrating geogra-
phical changes in North America,
51—54; .common to Alaska and
Asia, 83 ; of Florida, 175; of Ber-
muda, 191—194; of south-western
States, 205, 206; of Central
America, 256, 257; of Antilles,
265—274; of St. Helena, 389,
390; marine, absence of from
relict lakes, 49 ; Pacific, affinity to
English Crag species, 96 ; of West
Indies and Mediterranean, 278 ; of
western South America, 333, 334 ;
common to Patagonia and New Zea-
land, 428

Monachus, albiventer, 280 ; tropicalis,
280

Monkeys, distribution of, 249, 250 ; in
Santa Cruz beds, 400; capuchin,
364; squirrel, 364; sakis, 364 ;
spider, 364 ; howlers, 364

Moose-deer, 32, 33, 80, 92; former
range, 33; absent from Newfound-
land, 56; in Mackenzie region, 67

MO6rcuH, mollusks of Greenland, 21

MoRENO and WoopwarD, Neomylodon
listai, 400 -

Morphidae, 368, 369

Morse, discovery of Helix hortensis,
15 ; dispersion of European species
on American shores, 16

Moschogphoromys, desmaresti, 284 ;
luciae, 284

MOSELEY, on Bermudan flora, 187

Mouse, red-backed, 29 ; jumping, 29 ;
in Galapagos, 297

Mud-minnows in drift area, 51

**Mud-puppy,” 136

Murray, A., origin of Galapagos

fauna, 311; on beetles common to
Asia and America, 321; on south
Atlantic land-bridge, 381

Murray, J., on coral reefs, 327

Mus, sylvaticus, 24; galapagoensis,
297 ; decumanus, 298; rattus, 298

Musk-ox, present and former range,
6—9; variations of, 7; place of
origin, 7, 8; remains within drift
area, 43 ; in Mackenzie region, 59 ;
in Alaska, 78, 80

Musk-rat, 64, 153

Mussels, freshwater, 51—55 ; import-
ance of their distribution, 160—
162 ; of Central America, 254 ; affi-
nity between African and Brazilian,
338 ; of South America, 405

Mustela, atrata, 56; kenaiensis, 92 ;
arcticus, 92

Mutelidae, 168, 380

Mycetes, 364

Mylodon, 70, 153, 235

Myocastor coypus, 283, 396

Myrmeocystus, melliger, 216 ; mexi-
canus, 216

Myomorphus cubensis (see . Megaloc-
nus).

Myopotamus (see Myocastor).

Mysis, distribution and origin, 48 ;
relicta, 48 ; oculata, 48

N

Nabis capsiformis, 391

NANSEN, pre-glacial elevation of land,
14

Nasua, rufa, 249 ; olivacea, 249

NATHORST, on musk-ox, 7; effects of
Glacial Epoch on arctic flora, 17

Natriz (see Tropidonotus).

*“* NATURAL SCIENCE,” anonymous
writer on origin of reindeer, 4
Nebria gyllenhali, 24

Necrolestes, 246, 399, 404

Necturus maculatus, 136

NEHRING, relationship of Cervus cana-
densis, 68

NELSON, external features of Green-
land hare, 9; distribution of rabbits,
226 ; Tres Marias islands, 330

488

Nelsonia, 201

Nemorrhaedus, 83, 106

Nenia (see Clausilia).

Neocyclotus, 268

Neofiber, 64, 182

Neomylodon (see Grypotherium).

Neotomodon, 201

Nerhila, clavipes, 190 ; clavata, 191

Nesodon, 399

Nesolagus, 225

Nesomimus, 301, 315

Nesopelia, 301

Nesoryzomys, indefessus, 299 ;
boroughi, 299

Nesospiza, 393

Neuroptera of Florida, 178 ; of Cen-
tral America, 258 ; of Antilles, 289

Netirotrichus, 321; gibbsi, 201

Newfoundland, survival of fauna from
pre-glacial times, 41; geological
history, 55; fauna of, 56

Newgortia, 350

NEWTON, Falkland island fossils, 430

Nicaragua, Lake, fauna of, 240

Nicoletiella, 258

Nome, marine gravels at, 97

Nonionina depressula, 47

North-Eastern States, reptiles, 123—
135 ; amphibians, 185—139 ; flora,
139—141 ; mammals, 141—143

NORDENSKIOLD, on Mastodons, 408

Notiodrilus, 412 ; bovei, 431; fale-
landicus, 431

Notiosorex, 201

Notostylops, 400—402

Notropis, cornutos, 50 ; atherinoides,
50

Nova Scotia, land-bird fauna, 56

Nycterinus, 215

Nysius, 391

nar-

O

Ocean floor, composition of, between
America and Galapagos, 332

Oceanodroma cryptoleucura, 302

Ochotona collaris, 92

Octodontidae, 371

Odocoileus, origin of, 107—110, 396;
hemionus, 107; virginianus, 108,
396 ; columbianus, 108, avius, 109

INDEX

| Odonata, 258

Oeneis semidea, 36, 38

Oleacinae, 272 ©

**Olm,” 136

Oniscus asellus, 39

Oniticellus, 215

Onychodectes, 244

Onychomys, 201

Onychophora, 345—347, 432

Oreas, 380, 385, 393

Orhisaurus, distribution of, 281 ; ven-
tralis, 173, 221 ; apus, 173, 221

Oristhacanthus, 382

Opisthopatus, 346, 432

Opossum, range, 182; past history,
229 ; in West Indies, 283 ; in South
America, 366 ; in Santa Cruz beds,
403

OPPENHEIM, on Helicidae, 206

Oreamnos, origin of, 106 ; kennedyi,
92 ; montanus, 105

Oreohelix, 206

Oreotrochilus, 367

Orestias, 361, 362

Orthalicinae, 270, 273

ORTMANN, distribution of Cambarus,
177; distribution of freshwater
crayfishes, 217—220; Central Ameri-
can crabs, 239, 240; freshwater
crabs, 255; land-bridge between
Mexico and Cuba, 291 ; development
of Central America and Antilles,
292; origin of Galapagos, 314;
Miocene marine fauna of Peru, 334;
geological history of South ‘America,
339, 340; south Atlantic land-
bridge, 381—383; on Ihering’s Arch-
helenis, 382 ; on age of Santa Cruz
beds, 398 ; Chilean crayfishes, 405 ;
on Antarctic continent, 419, 420, 424

Orycteropidae, 373

Orycteropus, 372

Oryctolagus cuniculus, 225

Oryzomys, range of, 284 ; victis, 284;
antillarum, 284; galapagoensis, 299;
bauri, 299 ; nelsoni, 299

OsBoRN, connection between North and
and South America in Cretaceous
times, 71, 227 ; connection between
Asia and North America, 84, 319 ;
dispersal of camels, 86 ; distribu-

}

4 cs »< a > > idee
ee? | a a ao eee Ps

—S

INDEX

tion of fossil elephants, 87 ; origin of
Cervidae, 110; middle Miocene
fauna, 112; fossil-beds of western
America, 119, 120; faunal phases
in North America, 120—122 ; cause
of extinction of species, 146 ; Oligo-
cene horses, 147 ; Lower Pleistocene
mammals, 153; mammal horizons,
correlation of, 226, 227; Eocene

K affinities between Europe and North
America, 228; Oligocene affinities

jbetween Europe and America, 229,
230, 294, 357 ;, on Miocene and’ Plio-
cene faunas, 230, 231; origin of
Central America, 243 ; armadillo in
Eocene beds of North America, 244;
dispersal of manatees, 279 ; geo-
logical evolution of South America,
341, 342; origin of North Ameri-
can bears, 351; tapirs in North

America, 352, 353; Miocene. eden-
tates in North America, 358, 402,
409 ; Miocene sea in Amazon valley,
360 ; Eocene deposits in Patagonia,
367 ; on absence of land-connection
between South America and Old
World, 371; ancestors of camels,
407 ; Antarctic continent, 419

OscooD, reindeer in Alaska, 5; on
Scaphoceros, 155

Ostriches, present and former range,
373, 374

Otocryztops, 382

Otostomus (see Drymaeus).

Otter, in Newfoundland, 56 ; in Pleis-
tocene deposits, 153

Ovibos, distribution, 6—9, 86; an-
cestry, 154, 155 ;- moschatus mac-
henzianus, 59 -

Ovis, nivicola, 85, 86, 105 ; borealis,
86; canadensis, 104 ; scazhoceras,
105 ; cavifrons, 155

Oxystyla undata, 176

Oxytelus, 391

P

Pacific continent, evidence for the
former existence of, 321—328 ; pro-
bable subsidence before Tertiary
Era, 328

489

Pacific land-belt, theory of, 409, 410,
427—429 ; southern faunistic affi-
nities explained, 426

Pacific islands, geological formation
of, 322, 326

PACKARD, Labrador fauna and flora,
27; subterranean faunas, 165; South
Atlantic land-bridge, 381

Paddle-fish in Mississippi, 88, 89

PAGENSTECHER, affinities of Greenland
lepidoptera, 22; lepidoptera of
Rocky Mountains and Europe, 117;
butterflies of Florida, 179; Cali-
fornian butterflies and moths, 214 ;
on Antillean lepidoptera, 289

Palaemonetes, 291

Palaeolagus, 226

Palaeolama, 406

Palaeomastodon, 358

Palaeomeryx, 112

Palpigrada, 217

Panama, isthmus of, geology of, 236,
237 ; date of submergence of, 238;
sunken land westward of, 331

Pangolin, 372

Panolopus, 281

Panopeus bermudensis, 333

Paramylodon, 153

Parascalops breweri, 142

Parastacidae, 420, 424, 426, 432

Parastacus, 405

Pardosa groenlandica, 36

Parnassius, range of genus, 90, 91;
nomion, 90; sminthus, 90; thor,
90 ; clodius, 90 ; clarius, 90

Paroxya bermudensis, 189

Parrot, Florida, 159, 172 ; in Central
America, 250 ; showing affinity be-
tween. Africa and America, 373

Parus, 56

Patagonia, fossil fauna of, 398—404 ;
land-connection with western North
America, 402; affinities to south
Africa, Australia, and New Zealand,
405—416

Patula, solitaria, 72 ; striatella, 72

PAULCKE, cretaceous deposits in South
America, 359

PAULMIER (see ECKEL).

Peccary in North America, 153, 156 vA

Pectinator, 372

490

Pedetidae, 372, 373:

Pellegrinia, 372

Pelobates, 204 ; syriacus, 221

Pelobatidae, 204, 221

Pelodytes, 221

PENHALLOW, Pleistocene
Canada, 43, 44

Pentalagus, 225

Peratherium, 367

Perch, absent from western States, 198

Percidae, 198

Peripatus, range and origin of, 345—
347, 362, 432 ; eiseni, 346 ; goudoti,
346 ; tholloni, 369

Permanence of ocean basins theory,
214—232, 272—281, 321—333

Perodipus, 201

flora of

Peromyscus, maniculatus, 27; sit-
Rensis, 92
Peru, geological history of, 359 ;:

poverty of freshwater fauna, 405

PESCHEL, meaning of term “relict
lake,” 49

PETERSEN, Polar’ centre of distribu-
tion for butterflies and moths, 22

Petromys, 372

Pezzotettix, glacialis, 36; borealis, 36;
frigida, 36

PFEFFER, sub-universal distribution of
species, 374, 375; distribution of
Lepidosirenidae, 378

Phaeolaema, 350

Phasmidae, 158

Philomycus, 412

Philonthus, 391

Philoscia, bermudensis, 190; couchi,
190

Philyra pisum, 93

Phlaocyon, 151, 152

Phoca, 280

Phragmatobia jfuliginosa, 214

Phrynosoma, 127, 202

Phyllodactylus tuberculosus, 304

Pica, rustica, 87 ; nutalli, 88

PICKARD-CAMBRIDGE, Central Ameri-
can spiders, 258; spiders of St.
Helena, 388, 389

Pigidium rivulatum, 361

Pike, as evidence of old land-connec-
tion of America with Asia, 83 ;
“bony,” 89; in Mississippi, 163, 164

INDEX

PILSBRY, mollusks of Florida, 175,
176; mollusks of Bermuda, 191—
193 ; on eastern and western faunal
provinces, 198; family AHelicidae,
205, 206, 212; on Arionidae, 212,
213; on Urocoptidae, 267, 268 ;
geological history of Antilles, 267 ;
on groups of Bulimulus, 270, 307 ;
on Pacific continent, 322, 323 ; dis-
tribution of Achatinidae, 380 ; mol-
lusca of St. Helena, 390; Chilo-
nopsis, 390; convergence among
Bulimuli, 410; Helicigona’ and
Arianta, 411

** Pine-barren ” flora, 140, 141

Pinicola, 56

Pipa americana, 377

PIRIE, sedimentary rocks in South
Orkneys, 433

Pitymys, range implying great anti-
quity, 223, 224; incertus, 223 ;
quasitor, 224; pinetorum, 224;
nemoralis, 224

Placostylus, 209, 307

Plagiodontia, 282, 283

Plagiola, 254

Planorbis, nathorsti, 21 ; arcticus, 21 ;
noronhensis, 385

Plants, as tests of climate, 43, 175 ;
in Pleistocene beds, 44; of Rocky
Mountains, 114 ; common to eastern
States, Japan and Himalayas, 139 ;
affinity in mid-Cretaceous times be-
tween Argentina and Dakota, 414 ;
common to Rocky Mountains, and
southern South America, 415

Platatherium, 113

Platygonus, 153

Plectocyclotus, 268

Plekocheilus, aurissileni, 269; aula-
costylus, 269

Plestiodon, 123

Plethodon, 412 ; cinereus, 31

Pleurodonte, 272

Pliauchenia, 153, 407

Plover of St. Helena, 387

Plutonium, 350

Pocock, myriopods of Bermuda, 189 ;
distribution of scorpions, 382; on
affinity between western North
America and Argentina, 412

aa,

- INDEX

Podocnemis, distribution of, 374, 375 ;
expansa, 360

Poeciliidae, 166

Poecilozonites, 192, 193

Polar origin of life, 23, 24, 427, 428

Polygyra, 198, 205 ; monodon, 31

Polyodon spathula, 88

Pomadasis grandis, 241

Pontoporeia, hoyi, 49 ; filicornis, 49

Poprptus, distribution of arctic Coleop-
tera, 21

Porcellio garvicornis, 190

Porcupine, Canadian, 27, 69, 431 ;
South American, 366, 403

Porites, 239

Porrhyriornis, 393 :

Port Kennedy cave fauna, 153

Potamobiidae, 218—220, 426

Potamobius, 218—220

Potamocarcininae, 381

Potamoninae, 255, 381

Potos, 249 (See also Cercoleptes.)

Potter Creek cave fauna, 61, 153

Prairie-dog, 148

** Prairie-plains,”’ 144

Prairie-wolf, 148

Praticolella, 175

PREBLE, distribution of Zapus, 29 ; on
Hudson Bay region, 31; report on
Athabasca-Mackenzie region, 58

Prenolepis kincaidi, 189

Primates in North American Eocene
beds, 228, 230

Proboscidea, 230

Procazromys geayi, 283

Procellartidae, 302

Procyon, lotor, 151 ; simus, 152; may-
nardi, 181, 249

Procyonidae, 151, 152, 181, 249

Prolagostomus, 403

Prong-horn, range and ancestry of,
112, 113

Prophysaon, 212

Prorastomus veronensis, 280

Proscalops, 143

Protauchenia, 406

Proteidae, 136

Proteocordylus, 135

Proteodidelrhys, 367, 403

Proteus anguineus, 136

Protopterus, 378 ; libycus, 379

- Pseudothelphusa,

491

Protracheata (see Onychorhora).
Protylopus, 407
Pserhurus gladius, 89

‘ Pseudobranchus lateralis, 172, 173

Pseudoneuroptera of Antilles, 289
255, 362; colom-
americana, 291 ;

affinis, 291

biana, 256;
terrestris, 291 ;

Pseudopus, 380

Psittacidae, 373. -

Psittacotherium, 244

Ptarmigan, willow, 62; rock, 62

Pterosphenus, 278

Pudu, 354 ; in Chile, 418

Pudua mephistopheles, 354

Puma, 106, 107

Pupa in Galapagos islands, 306, 308 ;
in Fernando de Noronha, 385 ;
hoppei, 21; muscorum, 72; armi-
fera, 72 ; holzingeri, 72

PutnaM, fauna of Mammoth Cave,
164, 165

Putorius, pygmaeus, 85 ; riwosus, 85

Pyrameis, atalanta, 214; cardui, 214
Pyrotheria, 400
Q
QUACKENBUSH, mammoth. remains in
Alaska, 80
Quesal, 250
R

Rabbits, affinities and ancestry of, 225,
226

Raccoon, 151, 181, 249, 283

Raccoon-fox, 201

Rana, pipiens, 31; palustris, 31;

cantabrigiensis, 31; septentrionalis,
31

RANCE, DE (see FEILDEN).

Rangifer, tarandus, 3; spitsbergensis,
8; caribou, 3; stonei, 5; osborni,
5; montanus, 5, 92; terrae novae,
56; arcticus, 59

Rat on Galapagos islands, 298, 299

RATHBUN, distribution of Pacific
crustacea, 93, 94; freshwater
crabs of Central America, 255 ;
crabs of Peru, 333

492

Red-deer, origin of, 68

Red-fin in drift area, 50.

REGAN, on bony-pikes, 164; Central
American Cichlidae, 234 ; land-con-
nection between South America and
Africa, 379

Regulus, in Nova Scotia, 56 ;
persal, 114, 115; cuvieri,
satrapa, 115; calendula, 115

REHN and HEBARD, Bermudan Orthop-
tera, 189; Orthoptera of Florida,
179

Reindeer, forms of, 3, 4; original
home, 4, 5; extinct Irish, 12;
in Iceland, 12; former range in
Europe and America, 6, 35; in

' Newfoundland, 55

Reithrodon, 431

Relict lakes, explanation of term, 49

Rhamphastidae, 250, 368

Rhea, 373, 374, 396

Rhinema floridana, 173

Rhineura, 203

Rhinocerotidae, 229

RHOADS, structure of Greenland hare,
9

Rhorzalomesites, 178

Rhynchophora, 387

Rhynchopsittacus, 172

Rhysida, 382

Rice, geology of Bermuda, 184

Rice-rats, in Antilles, 284, 285; in
Galapagos, 298

RICHARDSON, isopods of Florida, 179 ;
isopods of Bermuda, 190

Ripeway, birds of Galapagos, 301

RIDLEY, on Fernando de Noronha, 384,
385

RIFFARTH (see STICHEL).

RopBINns and COCKERELL, on Veroni-
cella, 194

ROBINSON and GREENMAN,
Galapagos islands, 314, 315

Rockall Bank, shallow water species
dredged near, 17

Rocky Mountains, 100—104 ; plants
of in Southern Andes, 414—418

Roe-deer, affinity with American deer,
111

Romerolagus, 226

Roric, affinity of American deer, 111

dis-
115 ;

flora of

INDEX

RotH, fauna of Santa Cruz beds, 399,
400

ROTHSCHILD and HarRTeErRtT, birds of
Galapagos islands, 302

ROOSEVELT, land reserves in Rocky
‘Mountains, 118, 119

Rumina decollata, 192, 273

Rupicapra, 106

Rupicola crocea, 362

Ruscinomys, 372

RUSSELL, extent of American ice-sheet,
33 ; former drainage of Mississippi,
54; description of Rocky Moun-
tains, 102; absence of trees in
prairies, 145

RUTHVEN, prairie forms of animal
life, 145; origin and varieties of
garter-snakes, 128, 222

RUTIMEYER, on Antarctic continent,
420

RYDBERG, antiquity of Rocky Moun-
tain flora, 103

8

Salamander, giant, 135, 136 ;
136, 137; blunt-nosed, 136

Salamandridae, 136, 137

Salda, 391

SALISBURY (see CHAMBERLIN).

SALVIN and GopMAN, birds of Central
America, 250; insects of Central
America, 258

SALVIN, birds of Galapagos islands,
301

SANDBERGER, on Tertiary mollusks,
176 ; on Helicidae, 206

Santa Cruz fossil beds, 246, 398—404

SARASIN, on age of Coeciliidae, 251 ;
on age of Typhlopidae, 252, 288 ;
origin of Galapagos, 313 ; dispersal
of Herpele, 370 |

Saturnidae, 381

Sauresia, 281

Scalaria rugulosa, 428

Scalops aquaticus, 142

Scapanus, 201

Scaphiopus, 204, 220; holbrooki, 205

Scaphirhynchus, 83; platyrhynchus,
88

Scaphoceros tyrelli, 155

Scarabaeidae, 425

tiger,

INDEX

Sceloporus undulatus, 123, 126, 127
Schistomys, 403

SCHLOSSER, origin of reindeer, 4; on
value of zoogeographical evidence,

120, 223; geological age of Vis-
caciidae, 354

ScumiptT, fish fauna of northern Sea
of Japan, 94

SCHUCHERT, palaeogeography of Cali-
fornia, 198; palaeogeography of
North America, 228—231; on Cen-
tral America, 237, 238; antiquity
of Bahamas, 264, 293

ScHwaRzZ, Coleoptera of Florida, 178
geology of Ascension, 384

Scincidae, 123, 124, 189, 376

Sciuropterus, sabrinus, 63, 64 ; yukon-
ensis, 63, 92

ScLATER, W. L., and P. L. SCLATER,
distribution of seals, 280

Scoliopterix libatrix, 214

Scologendra morsitans, 382, 386

Scolopendridae, 382

Scorpions in Florida, 178 ; of western
America, 349, 350; of St. Helena,
389

Scort, on Cervalces, 32 ; Steiromys an
ancestor of Hrethizon, 71 ;Necro-
lestes, 246, 404; on Santa Cruz
fauna, 398—404 ; origin of eden-

tates, 401; Antarctic continent,
422

Seals, distribution of, 280; “ ele-
phant,” 428

Sea-urchins, fossil, of West Indian and
Mediterranean areas, 278

SEDGWICK, distribution of Onycho-
phora, 346°

Semotilus corgoralis, 51

SETON, mountain caribou, 5, 6; range
of moose, 32; range of wapiti, 67

SEWARD, fossil plants as tests of cli-
mate, 43

SHALER, effect of warm current on
Polar regions, 99; former eleva-
tion of Florida, 169

SHARPE, birds of Bermuda, 188, 189

Sheep, range of in America, 6; ex-
tinct, in Alaska, 80; in English
Forest Bed, 85; in Nicaragua, 105

SHIMEK, on Helicina, 158

493

Sialis bermudianus, 188

Siberia, fauna of, in Glacial times, 82

SIEBENROCK, distribution of turtles,
132

Siluridae, 380

SIMPSON, distribution of Unionidae,
52, 54; sub-divisions of Unionidae,
254 ; geological history of Florida,
177 ; Antillean molluscan fauna, 265
—267

Simpulopsis, 270

SIMROTH, on Arionidae, 213; mode
of dispersal of Amalia, 214 ; origin
of Bulimulidae, 273; pendulation
theory, 434

SINCLAIR, discovery of Huceratherium,
154; Santa Cruz fossil beds, 403,
404 ; Miocene beds in Oregon, 408,

. 409

Siren lacertina, 173

Sistrurus, 131

Sitta, 56

Skinks, 123, 189, 376

Skunks, western, 201

Sloth, in Brazil, 365, 366; ground,
244; giant ground, in North
America, 153, 156; in South
America, 400; gravigrade, re-
mains in leucdh, 408 .

SmitH, Edgar A., mollusca of St.
Helena, 389, 390
SmitH, Eugene A.,

Florida, 170
SmitH, G., Mysis relicta in Lake
Superior, 48
SmirH, Geoffrey, faunistic affinity of
Tasmania and South America, 424
SmitH, J. P., similarity of marine
faunas of Japan and America, 96 ;
geology of California, 199, 356, 357 ;
northern marine faunas, 318
Snakes in eastern North America,
127; garter, 127, 128, 222; rough
green, 130, 197 ; smooth green, 130
197; rattle, 131, 253, 352 ;

elevation of

burrowing, 252, 253; glass, 173,
221, 281; blind, 203

SNODGRASS and HELLER, birds of Gala-
pagos, 302

Solenodon, paradoxus, 282; cubanus,
282

°

494

Solenodontidae, 282

SoLLas, coral-boring at Funafuti, 321

** Sonoran ” region, 196

Sonorella, 206

Sorex, tundrensis, 92;
92; pribilofensis, 92

‘South America, northern animals in,
235; climate and fauna, 336, 337 ;
past geography, 338—345, 359, 360 ;
faunistic affinities of, 344—350 ;
affinity with European Tertiary
fauna, 3855; relationship with
Madagascar, 375; affinity with
Africa, 368—383

South Orkney islands, 433

South - Western States, 196; as
original home of eastern forms,
197 ; gradual desiccation of, 200—
204; affinity with Europe, 205—231.

Sparassodonta, 373

SPEIGHT, geology
islands, 327

Spelerpes, age of genus, 172, 221, 246;
in Antilles, 281 ; in South America,
347; orizabensis, 137; leprosus, 137;
chiropterus, 137 ; fuscus, 138, 221;
infuscatus, 281

SPENCER, pre-Glacial elevation of land,

- 14, 15; drainage of Great Lakes
in pre-Glacial times, 54; elevation
and submergence of Florida, 169,
170 ; Cuban cave fossils, 285 ; West
Indian land-bridge, 286 ; Antillean
continent, 293

Spermophilus (see Citellus).

SPETHMANN, land-bridge
Europe and Greenland, 18

Sphaeroniscus, 190

Stherilloninae, 320

Sphingidae, 117

Spider, silk, in Bermuda, 190, 191;
spiders of Central America, 258 ;
of St. Helena, 388, 389

Szinus, 56

STANDFUSS, affinities of Vanessa, 91

StapFr, arctic grasses found in Argen-
tina, 416

Staten island, 429

STEARNS, on Galapagos islands, 291 ;
accidental dispersal, 300, 306 ; mol-

_lusca of Galapagos, 305

glacialis,

of mid - Pacific

between

INDEX

STEBBING, on Cambaroides, 218

Steiromys, 71, 4038 .

STEJNEGER, on origin of reindeer, 5 ;
range of ptarmigan, 62; land-
bridge between Asia and North
America, 83; distribution of Cin-
clus, 113; distribution of ground-
lizard, 124 ; on Tropidonotus, 129 ;
discoglossoid toads, 204; Antillean
reptiles and amphibia, 288

Stenamma westwoodi, 215

Stenogyridae, 192

STEWART, botany of Galapagos, 315,
316

St. Helena, fauna, affinities of, 386—
391; flora, 391, 392

STICHEL and RIFFARTH,
contidae, 368

Stilauchenia, 406

Stimpson, Mysis relicta in
Michigan, 48

STOLL, mites of Guatemala, 257, 258

Stomion, 413

STRAND, distribution of arctic spiders,
21

STREBEL, on Orthalicinae, 270

Streptawidae, 348

Strobilops labyrinthica, 31

Strobilus, 272

Strophocheilus, 362

Struthio, 374

Sturgeon, shovel-nosed, 88

Stygicola dentatus, 290

Subulina, 272, 380

Succinea, in Galapagos, 306, 308; in
St. Helena, 390; groenlandica, 21,
24; bermudensis, 192, 193 ; barba-
densis, 192

** Suckers,”’ 89

SUESS, ancient land ‘‘ Laurentia,” 26 ;
absence of land-connection with
Asia in Pliocene times, 84; great
‘Pliocene subsidence of land, 195 ;
Cape Region of California, 199 ;
north Atlantic land-bridge, 229,
231 ; distinctness of Central
America from North and South, 237,
261; Antillean mountain system,
263 ; permanence of ocean basins,
276, 387 ; Galapagos islands a con-
tinuation of American mountain

on Heli-

Lake

"A.

ee ae ORY eee art ae

Pea

i

INDEX

chain, 297; ancient western rocks
in South America, 345; elevation
of Lake Titicaca, 361

“ Swift ” lizard, 123, 126, 127

Sylvilagus, 225

Symbos, 153—155 ; tyrelli, 80

Symbranchus marmoratus, 290

Synaptomys, innuitus, 27; sphag-
nicola, 37 ; cooperi, 28; wrangeli,
92 ; dalli, 92

Systemodon, 228, 353

Systrophia, 348

T

Talpa europaea, 142
Talpidae, 142, 143
Tamias caniceps, 92
Tapiridae, 228, 352, 353

Tapirus, americanus, 352 ; haysi, 352 ; |

arvernensis, 353

Tarantulidae, 382

Tayassus tetragonus, 156

TOHERSKI, wapiti deer and Siberian
maral, 68 ; conditions of climate in
Siberia in Glacial Epoch, 82 ; fossil
mammals in Siberia, 86

Teanopus, 201

Tehuantepec, isthmus of, 236

Teiidae, 369

Tenebrionidae, 215, 413

Tennessee river, alteration of its
course illustrated by distribution of
shells, 62

Teonoma saxamans, 92

Terrapene putnami, 134

Terrapin, 132.

Testudo, 315

Tetrabelodon, 231

Thamnophis, 128, 222; sirtalis, 127

Theatogps erythrocephalus, 217

Theridomyidae, 354

THOMAS, on meadow-voles, 224; dis-
covery of Caenolestes, 350

Thryonomys swinderianus, 372

Thylacinidae, 399, 403

Thylacinus, 399

Thynnidae, 433

Thysanophora hypolepta, 192, 193

495

Thysanura, 411, 412

Tierra del Fuego, faunistic affinity of,
429—431

Tillodontia, 244

Titicaca, Lake, 361

Tiger, sabre-tooth, 153, 200

Tityus floridanus, 178

Toads, in south-western States, 204 ;
spade-foot, 205, 220; tongueless,
377 ; Surinam, 377

Todies, 289

Toditae, 289

ToL, fossil mammals in Siberia, 82

Tomigerus, 389, 390 .

Tomocyclus, 269

Tornatellina, 306; chathamensis, 308

Tortoises, land and freshwater, in drift
area, 51; geological history of, 132,
222, 236 ; in Central America, 251 ;
of Galapagos islands, 302, 303, 312,
313; of Africa, Madagascar, and
South America, 374

Toucans, 250, 368

Tova, Tertiary fauna of Gatun, 238 ;
Tertiary fauna of Panama, 243

Toxodontia, 399

TRANSEAU, bog plant societies, 34

Tree-frog, Florida, 173

Tree-swifts, 368

Tremarctos ornatus, 350, 351

Trematherium, 366

Tres Marias islands, 330

Tribolonotus, 126

Trichechus, manatus, 279 ; inunguis,
279, 360 ; senegalensis, 279

Trichodina, 390

Trichoniscidae, 190

Triglorsis thompsoni, 49

Triloghodon, 259

Trinidad island, flora, 385, 386

Tristan da Cunha, flora and fauna,
393

Tristania, 393 .

TRISTRAM, polar origin of life, 23, 24

Trochilidae, 250, 367

Trogon, resplendens, 250 ;
250

Trogonidae, geological history of, 250

Troridonotus, range and age of, 128,
129, 222; validus, 222; vizerinus,
222

gallicus,

496

Tropidurus, 304, 315

TROTTER, origin of land-bird fauna of ©

Nova Scotia, 56

Truncatella, 176

Tudorella, 272

TULLBERG, dispersal of Microtus, 28 ;
origin of meadow-voles, 223; on

South Atlantic land-bridge, 372,
873, 405
Tundral fauna and flora, 35
Turkey, in North America, 159
Turritella, ambulacrum, 428; pata-

gonica, 428

Turtle, spotted, 132; diamond-back,
132; semi-box, 132; box, 134;
snapping, 134; alligator snapping,
135

Tylos, latreilli, 179, 190 ; niveus, 179,
190

Typhlichthys subterraneus, 165

sTythlomolge rathbuni, 136

Typhlopidae, 252, 253

Tyzthlops, tenuis, 253 ;
288

lumbricalis,

U

ULBRICH, distribution of Anemone, 114

Umbra, limi, 51 ; krameri, 51

Umbridae, 51

Unio luteolus, 162

Unionidae, distribution of, 161, 198,
254, 405 ; on Pacific slope of North
America, 162; groups of, 254; on
west of Andes, 338; of Chile and
New Zealand, 420

UpHam, elevation of north - eastern
North America, 41; elevation of
Lake Region, 54, 55

Urania leilus, 117

Urochroa, 350

Urocoztidae, 176, 206, 266

Uropoda, 258

Uropodias bermudensis, 190

Urotrichus, 321

Ursidae, 350

Ursus, americanus, 28; richardsoni,
61; middendorfi, 92; hkidderi,
92; dalli, 92; eulorhus, 92;

INDEX

kenaiensis, 92; emmonsi, 92;
- malayanus, 352; boeckhi, 352;
etruscus, 352
Uta, 127

Utah, lakes of, 103

Vv

VALLENTIN, Falkland islands, 430
VANATTA, Bermudan freshwater shells,
194; on Arionidae, 212
Vanessa, distribution of, 91;

117; antiora, 214
VANHOFFEN, survival of life in Green-
land during Glacial Epoch, 19
Varicella, 175
VAUGHAN, geology of Florida, 171
Venericardia glanicosta, 199, 357
Vernonia, 391
Veronicella, in southern Florida, 176 ;
schivelyae, 192, 194 ; moreleti, 194
VERRILL, Mysis relicta in Lake
Superior, 48 ; geology of Bermuda,
184, 185; Bermudan flora, 187 ;
Bermudan spider, 190; Central
American corals, 239
Vertigo, ovata, 72; ventricosa, 72
Vireo, bermudianus, 188; novebora- -
censis, 188
Viscacha, 358, 4038
Viscaciidae, 358, 403
Vitrea, 306, 308
Vitrina, angelicae, 21;
Voles, range of, 28; meadow,
224; Jalapa meadow, 224
Vulpes, lagopus, 11; deletrix, 56;
henaiensis, 92; rribilofensis, 92;
beringensis, 92

caradui,

limpida, 72
223,

W.

WALKER, distribution of Margaritana,
51; North American mollusca, 73 ;
mollusca of Florida, 177

WALLACE, age of fauna and flora of
New Zealand, 125; age of
Australian fauna, 150; Falkland
island wolf, 151; Bermudan fauna

| | INDEX 497

due to accidental dispersal, 183, 184,
188, 189 ; Central American fauna,

233, 234; appearance of southern -

forms in North America, 234 ;
northern element in South America,
235, 236, 259, 413 ; Antillean fauna,
261; Galapagos islands, 296, 298,
309 ; permanence of ocean basins,
274—277 ; faunal characteristics of
South America, 336, 337 ; antiquity
of continent of South America, 368 ;
St. Helena an oceanic island, 386,
387 ; fauna and flora of St. Helena,
388, 391, 392
WALTHER, on Pacific coast lines, 328
Wapiti deer, distribution and origin,
67—69
Water-vole of Florida, 182
Watson, flora of Californian islands,
417
Weasel, 85
WEBER, origin of Australian dog, 151
WEBSTER, dispersal of butterflies and
moths, 116
KR West Indies (see Antilles).
» WHEELER, Bermudan ants, 189;
honey-ants, 216 ; Liometopum, 216
Waite, C. A., on American Unionidae,
161
Waitt, F. B., Hemiptera of St.
Helena, 388, 390
WuittE, I. C. on geology of Argentina,
397
White Mountains, fauna and flora, 35
—37; relationship with Labrador
and Greenland, 42; with Rocky
Mountain flora, 103
WHITFIELD on fossil Unionidae, 161
WHITNEY, temperate climate in Glacial
Epoch, 19, 45, 46; climatic con-
ditions necessary to a Glacial Epoch,
75, 76; glaciation of Rocky Moun-
tains, 102
Wiser, Polar continent as origin of
life, 23
WINGE, on arctic hares, 9
WINKELEY, distribution of Helix
hortensis, 14
WoLr, Galapagos islands, 296 ; flora
of Galapagos, 309, 310

Wolf, arctic, 11 ; barren-ground, 61 ;
in Alaska, 61; Falkland island, 150,
430, 431; in South America, 396 ;
Tasmanian, 399, 403

WOLLASTON, beetles of St. Helena,
387

Wolverine, 61

Wood-chuck, 63

Wood-lice, 179, 190, 309

Wood-rats, 201 .

WoopwarD, A. S§., Grypotherium
listai, 401 ; Miolania, 404; on Pro-
rastomus, 280; on Bradytherium,
366. (See also MORENO.)

Woopwarkp, B. B., distribution of
marine mollusks, 16 (See also KEn-
NARD.)

Woopwakbp, 8S. P., on Atlantic land-
bridge, 272

Worm-lizard, 173

WortTMAN, North American origin of
Ganodonta, 244; origin of eden-
tates, 401

Wren, golden-crested, 114

WRIGHT, J., Foraminifera in boulder
clay, 47

Wricut, G. F., and UPHAM, survival
in Greenland of musk-ox,- 8 ; eleva-
tion of northern lands in Pliocene
times, 15

Wyoming, game preserve in, 119

x

Xantholinus, 391
Xenomys, 201
Xenopus, 377
Xenotherium, 246, 404

¥
Yagansia, 431
Yellowstone Park, 118 "4
Z

Zapus, hudsonius, 27, 29 ; setchuanus,
29 :

Zonitoides nitidus, 72

Zophobas morio, 390

BRADBURY, AGNEW & CO. LD., PRINTERS, LONDON AND TONBRIDGE.

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