in the Museum of Buenos Ayres. 85 
like the Peludo, have large hairs on their shells, these hairs issue 
from the junction of the plates. The others, which are termed 
Praopus, such as the Mulita (P. hybridus), have plates more 
or less unequal, covered with two classes of horny scutes, one 
large one in the centre on each side, and six smaller at ‘the 
junction of the plates. In these, the hairs which issue from the 
shell do not proceed from the joints, but from the same plate in 
the circumfererice of the central scute. 
The description of the shell of Glyptudon demonstrates that 
this antediluvian animal was constructed on the same principle, 
but that it resembled Praopus more than Dasypus ; nevertheless 
there is a difference between Glyptodon and Praopus, in con- 
sequence of the absence of the moveable rings in the middle of 
the shell, which the living Armadillos possess in varied number 
in the different species. 
There is an important difference in the surface of the shell be- 
tween Glyptodon tuberculatus and other species, G. tuberculatus 
not possessing the large hexagonal figures in the plates common 
to the other species. In G. tuberculatus the surface of each plate 
is covered equally with small irregular figures, upon which, 
without doubt, were placed concomitant horny plates, so that 
the superficies of the shell exhibits the same appearance. Some 
small holes amongst the small figures demonstrate also the ex- 
istence of hairs in the shell, but they are more sparse, although 
each plate also, in its original formation, appears to have pos- 
sessed six small apertures on its surface. On the edge of the 
shell are seen large hemispherical or conical tubercles, externally 
very rough, and covered with a smooth horny shield of the same 
form. The size of these tubercles varies according to their 
position in different parts of the edge, increasing in size towards 
the posterior part. On the shoulders chiefly these tubercles 
are more conical and sharp than those on the head and sides, 
where it appears to me there are some smaller and more conical 
moveable tubercles, below the edge of the shell and upon the 
legs. I have many of these tubercles in the Museum, but I am 
ignorant of their collocation on the body of the animal; never- 
theless M. Nodot states that his Schistopleurum had moveable 
rings at the side of the shell, which he has not recognized in 
any Glyptodon of the Museum, unless in the above-mentioned 
smaller tubercles. These, by the form of their basal parts, de- 
monstrate that they are placed on the same cutis, and are united 
to other parts of the shell. 
As a general character of the whole shell, it may be observed 
that the central plates become in time united in an entire piece, 
whilst those of the side are separated and united one to the 
other by joints. This separation of the plates continues until 
