THE
ZOOLOGY
OF
THE VOYAGE OF H. M. S. BEAGLE,
UNDER THE COMMAND OF CAPTAIN FITZROY, R.N.,
DURING THE YEARS
1832 TO 1836.
_PUBLISHED WITH THE APPROVAL OF THE LORDS COMMISSIONERS OF HER MAJESTY’S
TREASURY_.
Edited and Superintended by
CHARLES DARWIN, ESQ. M.A. F.R.S. SEC. G.S.
NATURALIST TO THE EXPEDITION.
PART I.
FOSSIL MAMMALIA:
BY
RICHARD OWEN, ESQ. F.R.S.
PROFESSOR OF ANATOMY AND PHYSIOLOGY TO THE ROYAL COLLEGE OF SURGEONS IN
LONDON; CORRESPONDING MEMBER OF THE INSTITUTE OF FRANCE, ETC. ETC.
LONDON:
PUBLISHED BY SMITH, ELDER AND CO. 65, CORNHILL.
MDCCCXL.
LONDON:
PRINTED BY STEWART AND MURRAY,
OLD BAILEY.
CONTENTS.
Page
GEOLOGICAL INTRODUCTION 3
TOXODON PLATENSIS, Description of Cranium 16
of Lower Jaw and Teeth 29
MACRAUCHENIA PATACHONICA, Cervical Vertebræ 35
Lumbar Vertebræ 40
Scapula 43
Antibrachium and Fore-foot 44
Femur 48
Tibia, Astragalus, and Metatarsal
Bone 50
GLOSSOTHERIUM, Fragment of Cranium 57
MYLODON DARWINII, Lower Jaw and Teeth 63
SCELIDOTHERIUM LEPTOCEPHALUM, Cranium and Teeth 73
Vertebral Column 84
Bones of the Extremities 88
MEGALONYX JEFFERSONII, Lower Jaw 99
MEGATHERIUM CUVIERI, Cranium and Teeth 100
TESSELATED ARMOUR AND BONES, large Edentata 106
MASTODON ANGUSTIDENS, Cuv. (?) 108
EQUUS, Molar Teeth 108
CTENOMYS PRISCUS, and a large Rodent 109
Geological contemporaneity of preceding extinct Mammalia 111
LIST OF PLATES.
PLATE I. Cranium of _Toxodon Platensis_, nat. size, basal view, with
the sixth molar, right side upper jaw, and grinding surface
of the seventh molar left side.
II. Cranium of _Toxodon Platensis_, side view.
III. Ditto, upper view.
IV. Ditto, back view, with two views of the sixth molar,
right side, upper jaw.
V. Fragment of lower jaw, and teeth of _Toxodon Platensis_.
VI. Cervical vertebræ of the _Macrauchenia Patachonica_.
VII. Ditto, ditto, and of _Auchenia Llama_.
VIII. Lumbar vertebræ of the _Macrauchenia Patachonica_.
_a._ Medium convex articular surface joining the body of the
sacrum.
_b._ Lateral concavities joining the transverse processes of the
_b._ sacrum.
_c._ Ossified ligament of an anchylosed lumbar vertebra.
IX. Fig. 1 and 2. Fragments of the Scapula.
Fig. 3. Distal end of the femur of _Macrauchenia Patachonica_.
X. Proximal ends of the anchylosed radius and ulna of
_Macrauchenia Patachonica_.
XI. Bones of the right fore-foot, _Macrauchenia Patachonica_.
XII. Femur, _Macrauchenia Patachonica_.
XIII. Anchylosed tibia and fibula, _Macrauchenia Patachonica_.
XIV. Right astragalus, _Macrauchenia Patachonica_.
XV. Fig. 1. External metatarsal bone of the right hind-foot.
Fig. 2. Proximal end of internal metacarpal bone, right
fore-foot.
Fig. 3 and 4. Proximal end of middle metacarpal bone.
Fig. 5. Proximal end of external metacarpal bone, right
fore-foot, _Macrauchenia Patachonica_.
XVI. Fragment of cranium of the _Glossotherium_.
Fig. 1. Side view.
Fig. 2. Base view.
Fig. 3. Inside view, all half natural size.
Fig. 4. Os tympanicum, natural size.
XVII. Fig. 1. _Megalonyx Jeffersonii._
Fig. 2. _Megalonyx laqueatus._
Fig. 3 and 4. _Mylodon Harlani._
Fig. 5. _Mylodon Darwinii._
XVIII. Lower jaw of the _Mylodon Darwinii_.
XIX. Fig. 1. Side view of the lower jaw.
Fig. 2 and 3. Last molar tooth.
Fig. 4. Front view of the symphysis of the lower jaw, _Mylodon
Darwinii_.
XX. Portion of the skeleton of the _Scelidotherium leptocephalum_.
XXI. Fig. 1. Side view of the cranium.
Fig. 2. Back view of the cranium.
Fig. 3, 4, and 5, anterior molar, upper jaw _Scelidotherium_.
XXII. Upper view of the cranium of the _Scelidotherium_.
XXIII. Fig. 1. Inside view of cranium.
Fig. 2. Articular surface for the lower jaw.
Fig. 3. Section of upper jaw and molar teeth.
Fig. 4. Section of lower jaw and molar teeth,
_Scelidotherium_.
XXIV. Cervical and anterior dorsal vertebræ of.
Fig. 1. _Scelidotherium._
Fig. 2. _Orycteropus._
Fig. 3. _Dasypus._
Fig. 4. _Myrmecophaga jubata_; all one-third nat. size.
XXV. Fig. 1 and 2. Humerus, radius and ulna of _Scelidotherium_.
Fig. 3. Head of humerus.
Fig. 4. Head of radius.
Fig. 5, 6, and 7. Femur of _Scelidotherium_.
XXVI. Fig. 1, 3, and 5. Astragalus of _Megatherium_.
Fig. 2, 4, and 6. Astragalus of _Scelidotherium_.
XXVII. Fig. 1 and 2. Patella and head of tibia of _Scelidotherium_.
Fig. 3, 4, and 5. Ungueal phalanx of _Scelidotherium_.
XXVIII. Fig. 1. Astragalus of _Megatherium_.
Fig. 2. Astragalus of _Scelidotherium_.
Fig. 3–6. Astragalus of _Mylodon_ or _Megalonyx_.
XXIX. Lower jaw of _Megalonyx Jeffersonii_.
XXX. Fragment of the Cranium of _Megatherium Cuvieri_.
XXXI. Section of the upper jaw and teeth of the _Megatherium
Cuvieri_.
XXXII. Fig. 1. Magnified view of structure of molar of _Megatherium_.
Fig. 2–5. Ungueal phalanx and portions of tesselated armour of
_Hoplophorus euphractus_.
Fig. 6–11. Jaws and teeth of _Ctenomys priscus_.
Fig. 12. Bones of right hind-foot of a Rodent.
Fig. 13 and 14. Fossil tooth of a Horse.
PREFACE.
His Majesty’s ship, Beagle, under the command of Captain FitzRoy, was
commissioned in July, 1831, for the purpose of surveying the southern
parts of America, and afterwards of circumnavigating the world. In
consequence of Captain FitzRoy having expressed a desire that some
scientific person should be on board, and having offered to give up part
of his own accommodations, I volunteered my services; and through the
kindness of the hydrographer, Captain Beaufort, my appointment received
the sanction of the Admiralty. I must here, as on all other occasions,
take the opportunity of publicly acknowledging with gratitude, the
obligation under which I lie to Captain FitzRoy, and to all the Officers
on board the Beagle, for their constant assistance in my scientific
pursuits, and for their uniform kindness to me throughout the voyage. On
my return (October, 1836) to England, I found myself in possession of a
large collection of specimens in various branches of natural history;
but from the great expense necessary to secure their publication, I was
without the means of rendering them generally serviceable.
The Presidents of the Linnean, Zoological, and Geological Societies,
having given me their opinion respecting the utility to be derived from
publishing these materials, I addressed a letter to the Right Honourable
the Chancellor of the Exchequer (T. Spring Rice, Esq.) informing him of
the circumstances under which I hoped that I might venture to solicit
the aid of Government. In reply, I received a communication (as below)
announcing to me that the Lords of the Treasury, from their readiness to
promote Science, were willing, under certain conditions, to give me the
most liberal assistance.
“_Treasury Chambers, August 31, 1837._
“SIR,
“It having been represented to the Lords Commissioners of Her
Majesty’s Treasury, from various quarters, that great advantage would
be derived to the Science of Natural History, if arrangements could be
made for enabling you to publish, in a convenient form, and at a cheap
rate, the result of your labours in that branch of science, my Lords
will feel themselves justified in giving their sanction to the
application of a sum, not exceeding in the whole one thousand pounds,
in aid of such a publication; upon the clear and distinct
understanding that the Work should be published, and the plates
engraved, in such a manner as to be most advantageous to the Public at
large, upon a plan of arrangement to be previously submitted to, and
sanctioned by the Board, after consultation with those persons, who,
from their attainments in this branch of science, are the most capable
of advising their Lordships thereupon; and that the payments on
account of the said sum of one thousand pounds are to be made to you
from time to time, on a certificate that such progress has been made
in the engravings, in accordance with the plan previously approved of,
as to justify the issue then applied for. My Lords have therefore
directed me to communicate to you the views they entertain upon this
subject; and to apprize you that they will be prepared to act in
conformity with their arrangement, upon learning from you that you are
ready to proceed with the Work upon the principles above laid down,
and upon receiving from you a statement of the manner in which you
think the Work should be published, and the plates engraved, so as
most effectually to accomplish the object my Lords have in view, in
sanctioning the payment from the Public Funds, in aid of the expenses
of the Work in question.
“I remain,
“Sir, Your Obedient Servant,
“A. Y. SPEARMAN.”
The object of the present Work is to give descriptions and figures of
undescribed and imperfectly known animals, both fossil and recent,
together with some account, in the one case, of their geological
position, and in the other of their habits and ranges. As I do not
possess the knowledge requisite for such an undertaking, and as I am,
moreover, particularly engaged in preparing an account of the geological
observations, made during the voyage, several gentlemen have most kindly
undertaken different portions of the Work. Besides the very great
advantage insured in thus enlisting the attainments of these Naturalists
in the several departments of science, to which they have paid most
attention, a great delay is avoided by adopting this method of
publication, which must otherwise have been incurred before the
materials could have been made known.
An Account of the Voyage, drawn up by Captain FitzRoy, (and to which I
have added a volume) being on the point of publication, I shall not in
this Work enter on any minute details respecting the countries which
were visited, but shall merely give a sketch of the geology in the
introduction to the part containing Fossil Mammalia, and a brief
geographical notice in that attached to the account of existing animals.
At the conclusion of this Work, I shall endeavour to place together the
leading results in the natural history of the different countries, from
which the collections were procured. I may here state that Mr. Owen has
undertaken the description of the Fossil Mammalia; Mr. Waterhouse, the
Recent Mammalia; Mr. Gould, the Birds; Mr. Bell, the Reptiles; and the
Rev. L. Jenyns, the Fish. Whatever assistance I may obtain in the
invertebrate classes, will be noticed in their respective places. The
specimens have been presented to the various public museums, in which it
was thought they would be of most general service: mention will be made
in each part where the objects described have been deposited.
FOSSIL MAMMALIA,
Described by
RICHARD OWEN, ESQ. F.R.S. F.G.S. F.L.S.
PROFESSOR OF ANATOMY AND PHYSIOLOGY TO THE ROYAL COLLEGE OF SURGEONS IN
LONDON; CORRESPONDING MEMBER OF THE ROYAL ACADEMY OF SCIENCES OF BERLIN;
OF THE ROYAL ACADEMY OF MEDICINE, AND PHILOMATHIC SOCIETY OF PARIS; OF
THE ACADEMY OF SCIENCES OF PHILADELPHIA, MOSCOW, ERLANGEN.
WITH
A GEOLOGICAL INTRODUCTION,
BY CHARLES DARWIN, ESQ. M.A. F.G.S. &c. &c.
CORRESPONDING MEMBER OF THE ZOOLOGICAL SOCIETY.
GEOLOGICAL INTRODUCTION.
BY MR. DARWIN.
Mr. Owen having undertaken the description of the fossil remains of the
Mammalia, which were collected during the voyage of the Beagle, and
which are now deposited in the Museum of the College of Surgeons in
London, it remains for me briefly to state the circumstances under which
they were discovered. As it would require a lengthened discussion to
enter fully on the geological history of the deposits in which these
remains have been preserved, and as this will be the subject of a
separate work, I shall here only give sufficient details, for the reader
to form some general idea of the epoch, at which these animals lived,—of
their relative antiquity one to the other,—and of the circumstances
under which their skeletons were embedded. All the remains were found
between latitudes 31° and 50° on the eastern side of South America. The
localities may conveniently be classed under three divisions, namely—the
Provinces bordering the Plata; Bahia Blanca situated near the confines
of Northern Patagonia; and Southern Patagonia.
The first division includes an enormous area, abounding with the remains
of large animals. To the eastward and southward of the great streams,
which unite to form the estuary of the Plata, those almost boundless
plains extend, which are known by the name of the Pampas. Their physical
constitution does not vary over a wide extent;—the traveller may pass
for many hundred miles on a level surface, without meeting with a single
pebble, or discovering any change in the nature of the soil. The
formation consists of a reddish argillaceous earth, generally containing
irregular concretions of a pale brown, indurated marl. This stone, where
most compact, is traversed by small linear cavities, and in several
respects resembles the less pure fresh-water limestones of Europe. The
concretions not unfrequently become so numerous, that they unite and
form a continuous stratum, or even the entire mass.
At Bajada de St^a. Fé, in the Province of Entre Rios, beds of sand,
limestone, and clay of different qualities, containing sharks’ teeth and
sea-shells, underlie the Pampas deposit. The shells, although numerous,
are few in kind. Mr. George B. Sowerby informs me that they appear to
belong to one of the less ancient tertiary epochs; they consist of
_Venus nov. spec._ near to _V. cancellata_; _Arca nov. spec._ near to
_A. antiquata_; a very large oyster, probably an extinct species; an
imperfect specimen of a second species of oyster near to _O. edulis_;
and a _Pecten_ near to _P. opercularis_. These beds pass upwards into an
indurated marl, and this again into the red argillaceous earth of the
Pampas, containing the remains of those extinct quadrupeds, which every
where characterize that deposit. To the southward of the Plata level
plains of an uniform composition, interrupted only at wide intervals by
hills of crystalline rock, extend to a distance of about three hundred
miles; and to the northward for at least an equal space, and probably
much further. As might have been expected from the perfectly level
surface, wherever a continuous section is presented on the banks of the
great rivers, very slight changes of colour show, that the deposit has
been accumulated in strata as horizontal as the land, or as the
water-line at the base of the cliffs.
In the province of Banda Oriental (to the N. and N. E. of the Plata),
and in part of that of Entre Rios, the land, though very low and level,
has a foundation of granitic and other primary rocks. These older
formations are partially covered, in most parts, by a reddish earthy
mass containing a few small calcareous concretions; while in other
parts, they are concealed by more regular strata, of indurated marl
passing into limestone, of conglomerates, and ferruginous sandstone. The
entire formation probably belongs to the same epoch with that of the
Pampas deposit. In the earthy mass, even where it is of little
thickness, and where it might readily be mistaken for detritus produced
from the underlying granites, remains of large quadrupeds have several
times been discovered.
On the shores of the Plata and in the neighbouring districts, proofs of
a change of level having taken place between the land and the water
within a recent period, may be observed. Both near Monte Video and
Colonia del Sacramiento, beds of shells are lying on the beach at the
height of several feet above the present tidal action. Near Maldonado I
saw estuary shells of recent species embedded in clay, and raised above
the level of a neighbouring fresh-water lake.
On the banks of the Parana, a shell identical with, or most closely
resembling an estuary species (_Potamomya labiata_, now living in that
part of the Plata, where the water is brackish) is accumulated in great
masses, which are found some miles inland, and are elevated several
yards above the level of the river. Sir Woodbine Parish, also, has in
his possession, shells procured from an extensive formation near
Ensenada de Barragan (south of Buenos Ayres), which is quarried for
lime. Mr. George Sowerby has examined these fossils, and says the
following are identical with living kinds; _Voluta colocynthis_,
Dillwyn: _V. angulata_, Swainson: _Buccinum globulosum_, Kiener: a
variety of _Oliva patula_: a _Cytheræa_ closely resembling or identical
with _C. flexuosa_, and a fragment of a second species, probably _C.
purpurascens_; _Potamomya labiata_; and fragments of oysters. There is,
however, a species of _Mactra_ in very great numbers, with which Mr.
Sowerby is wholly unacquainted. I may observe that I found recent shells
of the first five species inhabiting the coast, a short distance to the
southward. Some shelly limestone from the same place, which Sir Woodbine
Parish had the kindness to show me, resembles that which I saw at
Bajada, and in Banda Oriental. These beds, therefore, probably form
parts of the Pampas deposit, and are not merely indicative of the period
of its elevation. Nevertheless, on the opposite shores of the Plata,
near the mouth of the Uruguay, I found lines of sand dunes, where the
_Mactra_ and _Cytheræa flexuosa_ were lying in such quantities on the
bare surface, that the inhabitants, by merely sifting the sand, collect
them for burning into lime.
After these facts we may feel certain, that at a period not very remote,
a great bay occupied the area both of the Pampas and of the lower parts
of Banda Oriental. Into this bay the rivers which are now united in the
one great stream of the Plata, must formerly have carried down (as
happens at the present day) the carcasses of the animals, inhabiting the
surrounding countries; and their skeletons would thus become entombed in
the estuary mud which was then tranquilly accumulating. Nothing less
than a long succession of such accidents can account for the vast number
of remains now found buried. As their exposure has invariably been due
to the intersection of the plain by the banks of some stream, it is not
making an extravagant assertion, to say, that any line whatever drawn
across the Pampas would probably cross the skeleton of some extinct
animal.
At Bajada, a passage, as I have stated, may be traced upwards from the
beds containing marine shells, to the estuary mud with the bones of land
animals. In another locality a bed of the same mineralogical nature with
the Pampas deposit, underlies clay containing large oysters and other
shells, apparently the same with those at Bajada. We may, therefore,
conclude that at the period when the Arca, Venus, and Oyster were
living, the physical condition of the surrounding country was nearly the
same, as at the time when the remains of the mammalia were embedded; and
therefore that these shells and the extinct quadrupeds probably either
co-existed, or that the interval between their respective existences
was, in a geological point of view, extremely short. In this part of
South America there is reason to believe that the movements of the land
have been so regular, that the period of its elevation may be taken as
an element in considering the age of any deposit. The circumstance,
therefore, that the beds immediately bordering the Plata, contain very
nearly the same species of molluscs, with those now existing in the
neighbouring sea, harmonizes perfectly with the more ancient (though
really modern) tertiary character of the fossils underlying the Pampas
deposit at Bajada, situated at a greater height, and at a considerable
distance in the interior. I feel little doubt that the final extinction
of the several large quadrupeds of La Plata did not take place, until
the time when the sea was peopled with all, or nearly all, its present
inhabitants.
Bahia Blanca, situated in latitude 39°, and about 250 miles south of the
Plata, constitutes the second district, in which I found the remains of
quadrupeds. This large bay is nearly surrounded by very low land, on
which successive lines of sand dunes mark in many parts the retreat of
the water. At some distance inland a formation of highly indurated marl,
passing into limestone, forms an escarpment. Beyond this, rocks of the
same character extend over a wide and desolate plain, which rises
towards the flanks of the distant mountain of the Sierra de la Ventana,
composed of quartz. On the low shores of this bay, only two places
occur, where any section of the strata can be seen; and at both of these
I found fossil remains.
At Monte Hermoso, a line of cliff of about 120 feet in height, consists
in the upper part of a stratum of soft sandstone with quartz pebbles;
and in the lower of a red argillaceous earth, containing concretions of
pale indurated marl. This lower bed has the same mineralogical character
with the Pampas deposit; and possibly may be connected with it. The
embedded bones were blackened, and had undergone more chemical change
than in any other locality, which I examined. With the exception of a
few large scattered bones, the remains seemed to belong chiefly to very
small quadrupeds.
In another part of the bay, called Punta Alta, about eighteen miles from
Monte Hermoso, a very small extent of cliff, about twenty feet high, is
exposed. The lower bed seen at ebb tide, extends over a considerable
area; it consists of a mass of quartz shingle, irregularly stratified,
and divided by curved layers of indurated clay. The pebbles are cemented
together by calcareous matter, which results, perhaps, from the partial
decomposition of numerous embedded shells. In this gravel the remains of
several gigantic animals were extraordinarily numerous. The cliff, in
the part above high-water mark, is chiefly composed of a reddish
indurated argillaceous earth; which either passes into, or is replaced
by, the same kind of gravel, as that on which the whole rests. The
earthy substance is coarser than that at Monte Hermoso, and does not
contain calcareous concretions. I found in it a very few fragments of
shells, and part of the remains of one quadruped.
From the bones in one of the skeletons, and likewise from those in part
of another, being embedded in their proper relative positions, the
carcasses of the animals, when they perished, were probably drifted to
this spot in an entire state. The gravel, from its stratification and
general appearance, exactly resembles that which is every day
accumulating in banks, where either tides or currents meet; and the
embedded shells are of littoral species. But from the skeleton, in one
instance, being in a position nearly undisturbed, and from the abundance
of serpulæ and encrusting corallines adhering to some of the bones, the
water, at the time of their burial, must have been deeper than at
present. This conclusion might also have been inferred from the fact,
that in the neighbouring cliff the same bed, with its shells, has been
uplifted some yards above high-water mark. On the coast to the southward
abundant proofs occur, of a recent elevation of the continent. In the
gravel, nearly all the pebbles are of quartz, and have originally
proceeded from the lofty range of the Ventana, distant between forty and
fifty miles. Besides the pebbles of quartz, there are a few irregular
masses of the same indurated marl, of which the escarpment of the
neighbouring great plain is composed. Hence the gravel beds must have
been deposited, when the plain existed as dry land; and on it probably
those great animals once lived, of which we now find only the remains.
The indurated marl forming the plain, is the same kind of rock with that
occurring over a wide extent of the Pampas; and there is no reason to
doubt, they are parts of one great formation. Nevertheless, the gravel
bed of Bahia Blanca, although subsequent to the calcareous formation,
may be of the same age with those parts of the Pampas, which stand at a
low level near the Plata. For on this whole line of coast, I believe, as
the land has continued rising, fresh littoral deposits have been formed;
and each of these would often owe part of its materials to the
degradation of the one last elevated.
With respect to the relative age of the Monte Hermoso and Punta Alta
beds, it is not possible to speak decidedly. A certain degree of
similarity in the nature of the strata containing quartz pebbles, and
those of the reddish indurated earth; and the short distance between the
two localities, would indicate that no long interval had intervened. The
beds at Monte Hermoso, certainly were deposited more tranquilly, and
probably in a deeper sea; so that even skeletons of animals, no larger
than rats, have been perfectly preserved there. In some parts of the
surrounding country, obscure traces of a succession of step-formed
terraces may be observed; and each of these indicates a period of repose
during the elevation of the land, at which time the strata previously
existing were worn away, and fresh matter deposited. The Monte Hermoso
beds were, perhaps, formed during one such interval, anterior to the
accumulation of the shingle bank at Punta Alta.
Mr. G. Sowerby, who has been good enough to examine the shells which
were found with the remains of the quadrupeds, has given me the
following list.
1. _Voluta angulata._
2. —— _colocynthis._
3. _Oliva Brasiliensis._
4. —— Nearly related to _O. patula_, but specimen
imperfect.
5. —— Nearly related to _O. oryza_; less nearly to
small species now living at Bahia Blanca.
6. —— _Nov. spec._
7. _Buccinum cochlidium._
8. —— _globulosum._
9. —— One or two minute species, perhaps young
specimens,—unknown.
10. _Trochus_ _Nov. spec._ (?) same as one now living in
the bay.
11. —— _Nov. spec._ (?) nearly related to last;
differs in not being granular on the
surface.
12. _Assiminia_ (?) Minute species, identical with one living in
the bay.
13. _Bulinus nucleus._
14. _Fissurella_ Probably same as a kind (_nov. spec._ ?)
living in the bay.
15. _Crepidula muricata._
16. —— _Nov. spec._
17. _Cytheræa_ Closely related to, or identical with _C.
purpurascens_.
18. _Modiola_ Same as recent kind (_nov. spec._) living in
the bay.
19. _Nucula_ Near to _N. margaritacea_.
20. _Corbula_ Minute species, unknown.
21. _Cardita_ Ditto ditto
22. _Pecten_ _Nov. spec._ (?) very imperfect specimen.
23. _Ostrea_ Oysters of the same size now live in the
bay.
I may add that a fossil encrusting coralline is the same with one now
living in the bay.
Of these shells it is almost certain that twelve species (and the
coralline) are absolutely identical with existing species; and that four
more are perhaps so; the doubt partly arising from the imperfect
condition of the specimens. Of the seven remaining ones, four are
minute, and one extremely imperfect. If I had not made a collection (far
from perfect) of the shells now inhabiting Bahia Blanca, Mr. Sowerby
would not have known as living kinds, five out of the twelve fossils:
therefore, it is probable, if more attention had been paid to collecting
the small living species, some of the seven unknown ones would also have
been found in that state. The twelve first shells, as well as the four
doubtful ones, are not only existing species, but nearly all of them
inhabit this same bay, on the shores of which they are likewise found
fossil. Moreover, at the time, I particularly noticed that the
proportional numbers appeared closely similar between the different
kinds,—in those now cast up on the beach, and in those embedded with the
fossil bones. Under these circumstances, I think, we are justified
(although some of the shells are at present unknown to conchologists) in
considering the shingle strata at Punta Alta, as belonging to an
extremely modern epoch.
From the principle already adduced, namely, the regular and gradual
elevation of this part of the continent, I should have judged from the
small altitude of the beds at Punta Alta, that the formation had not
been very ancient. The conclusion here arrived at, concerning the age of
these fossil mammalia, is nearly the same, with that, inferred
respecting those entombed in the Pampas; and it will hereafter be shown,
that some of the species are common to the two districts. We may
suppose, that whilst the ancient rivers of the Plata occasionally
carried down the carcasses of animals existing in that country, and
deposited them in the mud of the estuary; other animals inhabited the
plains round the Sierra de la Ventana, and that lesser streams, acting
together with the currents of a large bay, drifted their remains towards
a point, where sand and shingle were accumulating into a shoal. The
whole area has since been elevated: the estuary mud of the former rivers
has been converted into wide and level plains; and the shoals of the
ancient Bahia Blanca now form low headlands on the present coast.
The third locality, which I have to specify, is Port St. Julian, in
latitude 49° 15′ on the coast of Southern Patagonia. The tertiary plains
of that country are modelled into a succession of broad and level
terraces, which abut one above the other; and where they approach the
coast, are generally cut off by a line of precipitous cliff. The whole
surface is thickly covered by a bed of gravel, composed of various kinds
of porphyries, and probably originating from rocks situated within the
Cordillera. The lower part of the formation consists of several
varieties of sandstone, and contains many fossil shells, the greater
number of which are not found in a living state.
The south side of Port St. Julian is formed by a spit of flat land, of
nearly a hundred feet in height; and on its surface existing species of
littoral shells are abundantly scattered. The gravel is there covered (a
circumstance which I did not observe in scarcely any other locality) by
a thin but irregular bed of a sandy or loamy soil, which likewise fills
up hollows or channels worn through it. In the largest of these channels
the remains of the single fossil quadruped, which was here discovered,
were embedded. The skeleton probably was at first perfect; but the sea
having washed away part of the cliff, has removed many of the bones,—the
remaining ones, however, still occupying their proper relative position
to each other. I am inclined to attribute the origin of this earthy
matter, to the mud which might have accumulated in channels, and on the
surface of the gravel, if this part of the plain had formerly existed as
a harbour, such as Port St. Julian is at the present day. The Guanaco,
the only large animal now inhabiting the wild plains of Patagonia, often
wanders over the extensive flats, which are left dry at the head of the
harbour during ebb tide: we may imagine that the fossil animal, whilst
in a like manner crossing the ancient bay, fell into one of the muddy
creeks, and was there buried.
I have stated that existing species of shells are scattered over the
surface of this plain; namely, _Mytilus Magellanicus_; a second and
undescribed species, now living on the beach; _M. edulis_; _Patella
deaurata_; and on another part of the coast, but having similar
geological relations, _Fusus Magellanicus_; _Voluta ancilla_; and a
_Balanus_:—these shells are among the commonest now living on this
coast. Although they must have been lying exposed to the atmospheric
changes for a very long period, they still partially retain their
different colours. From these facts we know, with certainty, that the
superficial deposit, containing the remains of the quadruped, has been
_elevated_ above the sea, within the recent period. From the structure
of the step-like plains, which front the coast, it is certain that each
step must have been modelled, subsequently to the elevation of the one
standing above it; and, as the same recent shells occur on two higher
plains, we may, with safety, conclude, that the earthy matter, forming
the surface of this lower one, together with its embedded skeleton, was
_deposited_ long after the existence of the present species, still
inhabitants of the sea. According, therefore, to the chronology, taken
from the duration of species among the molluscs, the fossil quadruped of
Port St. Julian must have been coeval, or nearly so, with those from
Bahia Blanca.
Having now briefly described the principal circumstances in the geology
of the three districts, to which I at first alluded, I will conclude, by
observing, that the fossil mammalia of La Plata, Bahia Blanca, and Port
St. Julian, must all have lived during a very modern period in the
geological history of the world. It is not the proper place in this work
to enter on any speculations, concerning the cause of the extinction of
so many gigantic animals. I will only here add, that there is the
strongest evidence against admitting the theory of a period of
overwhelming violence, by which the inhabitants of the land could have
been swept away, and destroyed. On the contrary every thing indicates a
former state of tranquillity, during which various deposits were
accumulating near the then existing coasts, in the same manner, as we
may suppose others are at this day in progress. The only physical
change, which we know has taken place, since the existence of these
ancient mammalia, has been a small and gradual rising of the continent;
but it is difficult to believe, that this alone could have so greatly
modified the climate, as to have been the cause of the utter
extermination of so many animals. Mr. Owen will mention the exact
locality where the remains of each quadruped were discovered; and, at
the conclusion, it will be easy to specify by name those, which, from
being embedded in the same deposit, are known formerly to have
co-existed on the continent of South America.
FOSSIL MAMMALIA.
BY MR. OWEN.
It may be expected that the description of the osseous remains of
extinct Mammalia, which rank amongst the most interesting results of Mr.
Darwin’s researches in South America, should be preceded by some account
of the fossil mammiferous animals which have been previously discovered
in that Continent. The results of such a retrospect are, however,
necessarily comprised in a very brief statement; for the South American
relics of extinct Mammalia, hitherto described, are limited, so far as I
know, to three species of Mastodon, and the gigantic Megatherium.
One of the above species of Mastodon (_Mast. Cordillerarum_) was
established by Cuvier[1] on remains discovered by Humboldt, in Quito,
near the volcanic mountain, called _Imbaburra_, at an elevation of 1200
toises above the level of the sea; and likewise at the Cordilleras of
Chiquitos, near Santa Cruz de la Sierra, a locality which is near the
centre of South America. A second species (_Mastodon Humboldtii_,
Cuv.[2]) is indicated by molar teeth, stated to have been discovered by
the same philosophic traveller, in Chile, near the city of Concepcion.
The third species of Mastodon appears to have once ranged in vast troops
over the wide empire of Peru: numerous teeth were brought thence to
Paris by Dombey,[3] and similar teeth, together with a humerus and tibia
from Santa Fé de Bogota were placed by Humboldt at the disposal of
Cuvier,[4] who considered them to belong to the _Mastodon angustidens_,
a species of which the fossil remains are by no means uncommon in
several localities of Europe. Cuvier is also disposed to refer to the
same species the teeth of the Mastodon from Brazil and Lima, mentioned
by Dr. W. Hunter in his observations on the _animal incognitum_ from the
Ohio.[5] The Megatherium has been scientifically described and
illustrated in the works of Bru, Cuvier, and D’Alton, whose accounts are
founded on a nearly complete skeleton of this stupendous quadruped which
has existed in the Royal Museum at Madrid for more than half a century.
The few deficiencies in its osteography have recently been supplied by
the descriptions and figures given by Dr. Buckland[6] and Mr. Clift,[7]
taken from remains of the Megatherium, brought by Sir Woodbine Parish
from Buenos Ayres, and which were discovered in the bed of the Rio
Salado, a tributary of the Rio Plata. Sir Woodbine Parish’s collection
from the same locality, includes also remains of other species of
extinct Edentata, which have not yet been described. M. D’Orbigny, in
his travels in South America (vol. i. p. 96.), states that, in the banks
of the Parana, he found the fossil remains of a large quadruped, of the
size of an Ox,—another quadruped of the size of a Cat, apparently of the
carnivorous order;—and a third, a Rodent as large as a Rat.
This meagre condition of the historical part of the subject of South
American fossils by no means arises from their actual scarcity. The
writings of some of the old Spanish authors, for instance, Torrubia,
Garcillasso, and others,[8] contain frequent allusions to the bones of
giants, who in times of old dwelt in Peru. Legentil, also, in 1728,
speaks as an eye-witness of these Peruvian remains; and his guides
pointed out to him the traces of the thunder-bolts, by which the Anaks
of the New World had been exterminated. Bones and teeth of the Mastodon
are, according to Humboldt, so abundant in a locality near Santa Fé de
Bogota in Columbia, that to this day it bears the name of the “Field of
Giants.”
But independently of these indications, the abundance and variety of the
osseous remains of extinct Mammalia in South America are amply attested
by the materials for the following descriptions, collected by one
individual, whose sphere of observation was limited to a comparatively
small part of South America; and the future traveller may fairly hope
for similar success, if he bring to the search the same zeal and tact
which distinguish the gentleman to whom Oryctological Science is
indebted for such novel and valuable accessions.
It is remarkable that all the fossils, collected by Mr. Darwin, belong
to herbivorous species of mammalia, generally of large size. The greater
part are referrible to the order which Cuvier has called Edentata, and
belong to that subdivision of the order (_Dasypodidæ_) which is
characterized by having perfect and sometimes complex molar teeth, and
an external osseous and tesselated coat of mail. The Megatherium is the
giant of this tribe; which, at the present day, is exclusively
represented by South American species, the largest (_Dasypus Gigas_,
Cuv.) not exceeding the size of a Hog. The hiatus between this living
species and the Megatherium, is filled up by a series of Armadillo-like
animals, indicated more or less satisfactorily by Mr. Darwin’s fossils,
some of which species were as large as an Ox, others about the size of
the American Tapir. The rest of the collection belongs, with the
exception of some small Rodents, to the extensive and heterogeneous
order Pachydermata; it includes the remains of a Mastodon, of a Horse,
and of two large and singular aberrant forms, one of which connects the
Pachydermatous with the Ruminant Order; the other, with which the
descriptions in the following pages commence, manifests a close affinity
to the Rodent Order.
A DESCRIPTION OF THE CRANIUM OF
TOXODON PLATENSIS;
_A gigantic extinct mammiferous animal, referrible to the Order
Pachydermata, but with affinities to the Rodentia, Edentata, and
Herbivorous Cetacea_.
The cranium, which is the subject of the present description, was found
in the Sarandis, a small stream entering the Rio Negro, and about 120
miles to the N. W. of Monte Video: it had been originally embedded in a
whitish argillaceous earth, and was discovered lying in the bed of the
rivulet, after a sudden flood had washed down part of the bank.
The zoological characters deducible from this cranium, forbid its
association, generically, with any known Mammiferous animal, and it must
therefore be referred to an extinct genus, which I propose to call
_Toxodon_,[9] from the curved or arched form of the teeth, as will
afterwards be described. The specific name, in the absence of other
means of knowing the peculiarities of the animal than those afforded by
the skull, may be most conveniently taken from the district (La Plata),
in which its remains were first discovered.
The dimensions of the cranium of the _Toxodon Platensis_ amply attest
that the animal to which it belonged was of a magnitude attained by few
terrestrial quadrupeds, and only to be compared, in this respect, with
the larger Pachyderms, or the extinct Megatherium. The length of the
skull (of which a base view of the natural size is given in Plate I.) is
two feet four inches: the extreme breadth one foot four inches. The
other requisite admeasurements are given in the table at the conclusion
of this description.
The general form of the skull, as seen from above, is pyriform; but
viewed sideways, and without the lower jaw, it is semi-ovate; it is
depressed, elongate, of considerable breadth, including the span of the
zygomatic arches, but becoming rather suddenly contracted anterior to
them, the facial part thence growing narrower to near the muzzle, which
again slightly expands.
Among the first peculiarities which strike the observer, is the aspect
of the plane of the occipital foramen, and of the occipital or posterior
region of the cranium, the latter of which inclines from below upwards
and forwards at an angle of 50° with the basal line of the skull. This
slope of the back part of the skull is one of the characteristics of the
Dinotherium; it is common to all the Cetacea, and is met with in a
slighter degree in many Rodentia, and in the great Ant-eater and some
others of the Edentate order. The corresponding aspect of the _foramen
magnum_ presents nearly the opposite extreme to man in the occipital
scale, proposed by Daubenton to determine the diversities of the form of
the cranium, as a gage of the intelligence of different animals[10]; and
the indication of the limited capacity of the Toxodon, thus afforded, is
strengthened by the very small proportion, which the bony walls of the
cerebral cavity bear to the zygomatic and maxillary parts of the skull,
and to the size of the vertebral column, as indicated by the condyloid
processes, and foramen magnum.
The zygomatic arches are of remarkable size and strength; they commence
immediately anterior to the sides of the occipital plane, increase in
vertical extent as they pass outwards, forwards and downwards, and are
suddenly contracted as they bend inwards to abut against the sides of
the sockets of the two posterior molar teeth.
The cranial cavity is remarkably narrow at the space included by the
zygomatic arches; being, as it were, excavated on each side to augment
the space for the lodgment of the temporal muscles, so that its diameter
at this part is less than that of the anterior extremity of the upper
jaw. The upper surface of the cranium expands to form the post-orbital
processes, and again contracts anterior to these.
The muscular ridges, or other characters, at the top of the skull,
cannot be precisely determined, as a great proportion of the outer table
of the bone is broken away, exposing a coarse and thick diplöe. There
seems, however, to have been a strong ridge separating the occipital
from the coronal or upper surface of the cranium. The form of the
remaining parts, which are modified in relation to the attachment of the
muscles of the jaws, indicates that these were powerfully developed both
for the offices of mastication and prehension. The general form of the
skull, while it presents certain points of resemblance to that of the
aquatic Pachydermata, and even of the Carnivora, has much that is
peculiar to itself; but, in the facial part, it approaches the nearest
to that of the Rodentia; and the dentition of the Toxodon, as exhibited
in the upper jaw, corresponds with that which characterizes the Rodent
Order.
The teeth of the Toxodon consist of molars and incisors, separated by a
long diastema, or toothless space. In the upper jaw the molars are
_fourteen_ in number, there being seven on each side; the incisors
_four_, one very large, and one small, in each intermaxillary bone.
The general form and nature of the teeth are indicated by the sockets;
and the structure of the grinders is exhibited in a broken molar, the
last in the series on the left side of the jaw of the present cranium
(See a figure of the grinding surface restored of this tooth, fig. 2,
Pl. I.), and by another perfect molar, the last but one on the right
side of the upper jaw, which, though not belonging to the same
individual as the skull here described, undoubtedly appertains to the
same species. This latter tooth (Fig. 3, Pl. I.; figs. 2 and 3, Pl. IV.)
was found by itself, embedded in the banks of the Rio Tercero, or
Carcarana, near the Parana, at the distance of a hundred and eighty
miles from the locality where the head was discovered. Fragments of a
molar tooth of a Toxodon, apparently the seventh of the left side, upper
jaw, were also found at Bajada de St^a Fé, in the province of Entre
Rios, distant forty miles from the mouth of the Rio Tercero.
All the molar teeth are long and curved, and without fangs,[11] as in
most of the herbivorous species of the Rodent Order: in those, however,
with curved grinders, as the _Aperea_ or Guinea-pig, and _Cavia
Patachonica_, the concavity of the upper grinders is directed outward,
the fangs of the teeth of the opposite sides diverging as they ascend in
the sockets; but, in the Toxodon, the convexity of the grinders is
outward, and the fangs converge and almost meet at the middle line of
the palate, forming a series of arches, capable of overcoming immense
resistance from pressure. (See the upper view of the skull, Plate III.,
in which the fractures expose to view a part of the series of these
arched sockets.)
Of the incisors, the two small ones (the sockets of which are indicated
at _s s_, Pl. III.) are situated in the middle of the front of the upper
jaw, close to the suture between the intermaxillaries, and the two large
ones in immediate contiguity with the small incisors, which they greatly
exceed in size. The sockets of the two large incisors (_t t_, Pl. III.)
extend backwards, in an arched form, preserving a uniform diameter, as
far as the commencement of the alveoli of the molar teeth: the curve
which they describe is the segment of a circle; the position, form, and
extent of the sockets of these incisors are the same as in those of the
corresponding teeth of the Rodentia.
The matrix, or secreting pulp of the large incisors, was lodged, as in
the Rodentia, in close proximity with the sockets of the anterior
molars; and we are enabled to infer, from the form of the incisive
sockets, notwithstanding the absence of the teeth themselves, that the
pulp was persistent, and that the growth of these incisors, like those
of the Rodentia, continued throughout life.
This condition, joined with the form and curvature of the socket,
implies a continual wearing away of the crown of the tooth by attrition
against opposing incisors of a corresponding structure in the lower jaw:
and as a corollary, it may be inferred that the teeth in question had a
partial coating of enamel, to produce a cutting edge, and were, in fact,
true _dentes scalprarii_. The number of incisors in the upper jaw of
Toxodon, is not without its parallel in the Rodent Order, the genus
_Lepus_ being characterized by four, instead of two superior incisors,
which also present a similar relative size but have a different relative
position, the small incisors, in the hare and rabbit, being so placed
immediately behind the large pair, as to receive the appulse of the
single pair of incisors in the lower jaw.