88 Dr. Burmeister on the Species of Glyptodon 
and a curved tube at its posterior portion. How many rings 
there were I do not know, as all the tails met with up to this 
time are broken; but it is very probable that the number of the 
rings of the tail were equal in all the species, that is to say, six. 
Each ring bears two or three bands of plates much finer than 
those of the shell, and of oblong form, each one presenting an 
elliptical scute in the centre and angular ones in the peri- 
phery. The figures here are almost smooth, and are deficient in 
the superficial rough structure of the shell. The posterior part 
of the tail forms an almost cylindrical tube a little curved, and 
thicker at the base than at the obtuse point. The surface 
of this tube has the same elliptical figures as the rings at the 
base, and between them a band of other, angular and much 
smaller figures. At the sides of this tube the ellipses change 
more or less into circles, and on the side itself is formed another 
band of much larger ellipses, which augment in size gradually 
to the point of the tail, the two immediately at the end being 
the largest. 
The third species from Buenos Ayres is G. tuberculatus, 
which M. Nodot has erected into a separate genus—Schisto- 
pleurum*, The different form of the plates on the surface of 
the shell above described easily distinguishes this group from 
the others. It is the largest of the three, and is double the size 
of G. spinicaudus. We only possess in the public Museum some 
pieces of the shell, and the posterior portion of the tail, of the 
general form of which we are consequently ignorant. M. Nedot 
states that at the edge of the shell there are some bands of 
moveable plates, and that for this reason he has separated this 
species from the others to form a particular group. There are in 
the Museum some plates of oblong form, with a large elliptical 
figure on the surface, and other smaller and irregular ones on the 
periphery. These plates form a kind of large ring, which is proba- 
bly one of the moveable parts of the side of the shell. But it 
appears to me that it belongs to the posterior edge of the shell 
from which issues the tail, for ming between the poster ior cylin- 
drical part of the tail and the shell some moveable rings, as in 
the other species. How many rings there were I do not know; 
but it is permissible to believe that there were six. The posterior 
portion of the tail of the animal which we have in the Museum 
is complete, and is 1 yard in length and 5 inches in breadth ; 
its superficies is covered with the same small irregular figures 
as the shell; but between them we can see large ellipses 2 as In 
the rings described. These ellipses are very different in pattern 
* [Now well known in England by Mr. Gregory’s excellent restoration. 
—TRANSL. | 
