84. Dr. Burmeister on the Species of Glyptodon 
supplements in the same periodical of the 25th of July, referring 
to the general description of the specimen in our museum, pub- 
lished by me in the ‘ Nacional’ of last year, No. 3140. 
Entering now upon the description of the specimens in the 
Public Museum of Buenos Ayres, it appears to me necessary to 
keep in mind that the number of species in our formations are 
not more than three, which are distinguished by the structure 
f the plates on the surface of the shell, and even by the general 
form of the shell itself. These plates form regular hexagons in 
the centre of the buckler, changing at the sides into prolonged 
hexagons, and very often into pentagons at the edges. In the 
same manner the hexagonal figures are arranged on the surface 
of each plate. There are seven on each plate, one (the largest) 
in the centre, and six on the six sides, which are in contact with 
the contiguous plates to form other hexagons on the joints be- 
tween them. These figures are separated by grooves, and in 
these are discerned, in the corners of a median hexagon, small 
apertures to receive ‘the roots of the long hairs which pass through 
the shell of the living Armadillo. The surface of each hexagon 
is rough hike a file; and upon this asperity a smooth horny 
shield existed, as in the existing Armadillos. But the size of 
these hexagons of each plate varies in the different parts of the 
shell, those in the centre being relatively more equal, and the 
peripheral portions more unequal, in such manner that the cen- 
tral hexagon of the plates occupies more space towards the 
centre of the shell, whilst these proportions diminish towards 
the edges. It results that the last plates at the edge of the 
shell form large, nearly circular hexagons, and in the circum- 
ference alone are some very small figures which form the half 
of the peripheral hexagons. In this way the collocation of 
the loose plates in the whole shell can be ascertained; but in 
no way are we able to constitute specific differences on the form 
of the entire plates or the figures on their surfaces. 
The same difference between the size of the central figure 
and the peripheral ones of each plate may also be recognized i in 
some existing Armadillos, as in the Mulita, which possesses the 
same structure of the shell—a fact which is demonstrable on 
the smooth horny scutes which cover the hexagonal pattern of 
the plates. 
These existing animals are to be met with in South America 
alone, like the antediluvian Glyptodon of other times, and are 
divisible into two principal classes. One, which naturalists term 
Dasypus, comprises such species as the Peludo (D. setosus), the 
Mataco (D. conurus), and the Pichy (D. minutus), with plates 
almost equal in all the parts of the shell, and covered with 
smooth horny scutes of the same pattern and size. If some, 
