not, as in the Sloths, to carry the animal to the food, but to bring the food within
the reach o f the animal, by uprooting the trees on which it grew.
In the remains o f the Megatherium we have evidence o f the frame-work o f a
quadruped equal to the task of undermining and hawling down the largest members
o f a tropical forest. In the latter operation it is obvious that the immediate
application o f the anterior extremities to the trunk o f the tree would demand a
corresponding fulcrum, to be effectual, and it is the n ece ssity for an adequate
basis o f support and resistance to such an application of the fore-extremities
which gives the explanation to the anomalous development o f the pelvis, tail, and
hinder extremities iu the Megatherioid quadrupeds. No wonder, therefore, that
their type o f structure is so peculiar ; for where shall we now find quadrupeds
equal, like them, to the habitual task o f uprooting trees for food ?
DESCRIFTION OF FRAGMENTS OF BONES, AND OF OSSEOUS TESSELATED DERMAL
COVERING OF LARGE EDENTATA.
I t is now determined that there once existed in South America, besides the Megatherium,
the Megalonyx, and the allied genera described in the preceding pages
o f the present work, gigantic spe cie s o f the order B ru ta belonging to the Armadillo
family, and defended, lik e the small ex isting representatives o f that family,
b y a tesselated bony dermal covering. Th e largest known spe cie s o f these
extinct Dasypodidce is the Glyptodon clavipes, o f -which the armour and parts o f
the skeleton have been described by MM. Weiss and D ’Alton in the Berlin
Transactions for 1827 and 1834: and the generic and specific characters and
name, with an account o f the dental system, and bones o f the extremities, were
recorded in the Geological Proceedings for March J839. It would seem that
parts o f the same, or a nearly allied gigantic spe cie s were described in the same
year by M. Lund ; under the name o f Hoplophorus. O f the valuable and interesting
discoveries of this able Naturalist I regret that I was not aware until the
appearance o f a notice o f them in the Comptes Rendus for April, 1839.*
Amongst the fragments o f bony tesselated armour in Mr. Darwin’s collection are
a few piec es whic'h were found by him, associated with remains o f Toxodon and
Glossotherium near the Rio Negro in Banda Oriental, j' Th ese fragments, if we
may judge from their thickness, must have belonged to an animal at lea st as
* An excellent translation of the description of the Brazilian fossils found by M. Lund, ia published in the
Annals of Natural History, Ju ly and August, 1839.
+ At the distance o fa few leagues from the locality here mentioned, other fragments were found by Mr.
Darwin j also near Santa Fe, in Entre R io s; also on the shores of the Laguna, near the Guardia del Monto,
South of Buenos Ayres ; also, according to the Jesuit Falkner, on tlie banks of the Tercero.
FOSSIL MAMMALIA. 107
large as the Glyptodon clavipes; but the pattern differs in the greater equality of
size o f the component tesserae. T h e thickness o f the largest fragment is one
inch and a half, the tesserse vary in diameter from one inch to ha lf an inch, and
are separated by grooves about two lines in depth, and two in diameter. The
pattern formed b y the anastomosis o f these grooves is an irregular n et-w o rk ; the
contour o f the tesserae is either unevenly subcircular, hexagonal, pentagonal,
or even four-sided ; with the sides more or le ss unequal. In those portions o f
this armour, where one o f the tesserae exc eeds the contiguous ones in size, the
imagination may readily conceive it to be the centre o f a rosette, around which
the smaller ones arrange themselves, but there is no regular sy stem o f rosettes,
as in the portions o f the dermal armour o f the Glyptodon figured by Weiss,
and those brought to England b y Sir Woodbine Parish, in which the central
piec e is double the size o f the marginal ones.
The portions o f the tessela ted bony dermal coveringof a Dasypodoid quadruped,
figured in PL X X X I I . figs. 5 and 4, o f the natural size, were discovered folded
round the middle and ungueal phalanges, figs. 2 and 3, at Punta Alta, in
Bahia Blanca, in an earthy bed interstratified with the conglomerate containing
the remains o f the fossil Edentals.
In one o f these fragments, measuring six inches long b y five broad, the tesserie
are arranged in rosettes, and so closely correspond in siz e and pattern witli the
bony armour described by M. Lund, as characterizing his spe cie s, Hoplophorus
euphractus, that I feel no hesitation in referring them to that animal. One o f the
pattern rosettes is figured at fig. 4, together with the thickness of the armour at
this part, and the coarse tubulo-cellular structure o f the bone. Another portion
o f dermal armour from the same locality, gives the pattern shown in fig. 5, formed
b y square or pentagonal tesseree, arranged in transverse rows ; it is certain that
this portion o f armour belonged to the same animal as the preceding p ie c e ; and
probably that it constituted part o f the transverse dorsal bands o f the Hoplophorus.
The middle and ungueal phalanx, as well as the portions o f armour, are given
o f the natural size, in PL X X X I I . The upper and outer surface o f the phalanx,
is shown in fig. 2. It is smooth and f la t ; jo ins the inner surface by a sharp edge,
which runs along the upper and inner side o f the bone ; and pa sses b y a gradual
convexity to the under surface ; the ridge corresponding with the base o f the claw,
is feebly developed at the under and lateral parts o f the base o f the claw. Below
the double trochlear jo in t for the middle phalanx, there are two articular surfaces
for two large sesamoid bones.
Th e middle phalanx corresponds in its small antero-posterior diameter and
wedge-shape, with that o f the great Glyptodon : but the terminal phalanx is longer
and deeper, in proportion to its breadth.