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ture of the teeth, but in the number, which appears to be eight on 
each side of each jaw; and from all known Armadillos in the form 
of the lower jaw, as well as in the presence of a long process de- 
scending from the zygoma, in both which respects it resembles the 
Megatherium. According to the same figure, the tail was protected 
by a narrow bony covering on the upper surface only, and was net 
encompassed by it as in the Armadillos. 
Mr. Owen then proceeds to describe the remains of the Glyptodon 
which have arrivedin England. The molar tooth is only a fragment, 
but the grinding surface and upwards of an inch of the crown are 
perfect, the whole length being about two inches. There is no in- 
dication of a diminution in any of its diameters from the grinding 
surface to the opposite end, and the alveoli in the fragment of the 
jaw terminate abruptly without any contraction. The teeth are 
more compressed than those of the Megatherium, and differ from 
them in intimate structure, resembling in this respect the teeth of 
the Armadillos. From all known Armadillos, the Glyptodon, how- 
ever, is distinguished by the tooth having on both the outer and inner 
surfaces two deep grooves, each extending from the opposite sides 
about one third of the transverse diameter of the tooth and through 
its whole length, dividing the grinding surface into three portions, 
joined together by the contracted isthmus interposed between the 
opposite grooves. The teeth thus exhibit a more complicated form 
than those of any known Edentate, and seem to indicate a transition 
from that family to the Pachydermal Toxodon. 
The fragment of the jaw discovered at Villaneuva consists of a 
portion near the extremity of the left ramus, and includes three 
alveoli, which slightly increase in size as they are placed further 
back. 
The humerus, of which the distal half has been received, agrees 
most nearly with that portion of the humerus of the Dasypus, but 
the internal condyle is not perforated; the depressions also above the 
trochlea, both in front and behind, are relatively deeper, and in the 
side opposite the deltoid trochanter there is a rugged raised surface 
for a muscular insertion, of which Mr. Owen has not perceived any 
thing analogous in the Armadillos. From the humerus of the Me- 
gatherium it differs in not presenting the extraordinary expansion of 
the distal extremity exhibited in that animal; but the internal con- 
dyle in the Megatherium is also imperforate. 
The radius of the Glyptodon corresponds very nearly with that 
of the Armadillo, but it differs from the radius of the Megathere in 
being three times less in every dimension, and by well-marked dif- 
ferences in all the details of structure. 
The ungueal phalanges of the Glyptodon approach most nearly 
those of the species of Dasypus; but in their shortness, as compared 
with their breadth and depth, they resemble still more the ungueal 
phalanges of the Pachyderms. Mr. Owen is of opinion that they 
were encased in strong, short, hoof-like claws; and that they exhibit 
rather the base of an anterior column of support to an animal clad 
in a ponderous cuirass than instruments especially designed for 
