86 Dr. Burmeister on the Species of Glyptodon 
the adult state of the animal, and for this reason the shells are 
generally fractured or broken on the edges. Complete shells, 
with all the parts and tubercles on the edges, are very scarce, 
and rarer in proportion to the youth of the animal. 
As regards the specific differences between the Glyptodons of 
this country, I cannot distinguish amongst our rich collection 
of Buenos Ayres more than three—G. clavipes, Owen, G. tuber- 
culatus, Owen, and a species which I provisionally name G. spine- 
caudus, for want of the original works which describe other 
species. 
The most abundant amongst these three species is the last, of 
which we have in the Museum an almost entire shell, a complete 
skeleton, and more or less important remains of three individuals. 
The species is distinguished easily by its short and conical tail, 
having seven rings of large conical tubercles ; and for this reason 
I have given it the name of G. spinicaudus. Probably the G. 
ornatus is identical with this species. As the shape of the tail 
is the most important feature, we shall begin with its descrip- 
tion. 
It is 22 inches in length, 14 in width at the base, and 
A at the apex, which is obtuse and round. At the base are 
seen six rings of conical tubercles, which are more or less narrow. 
Each ring is composed of three bands of plates, the last one 
being formed of the great tubercles, whilst the two preceding 
ones are smooth, and almost wholly covered by the anterior 
rings. The first ring is the largest, and of a transversely ellip- 
tical shape, having twenty-three tubercles on the posterior edge, 
the nine lower ones being smooth, and the upper ones more 
elevated into a conical point according as they approach the 
middle of the dorsal surface. The second ring is of an almost 
circular figure, and with eighteen tubercles on the edge, the 
inferior surface being smooth in almost all the lower rmgs. In 
the same manner, the third ring has fifteen, the fourth eleven, 
the fifth nine, the sixth seven tubercles; and the extreme por- 
tion is formed by a ring of five, including amongst them three 
at the apex itself. Of all these tubercles, those of the middle of 
the dorsal surface are always the largest, and prolonged into a 
conical point. The shell of this species is in its general form 
more spherical than that of some of the others. Its length, follow- 
ing the curve, is about 34 yards (varas), and its width about 24; 
only the posterior part near the tail is a little uncovered; the 
longitudinal diameter is 54 feet, and the transverse diameter is 
about 34. The surface of the plates is very rough, much more so 
than in the other species, and the size of each plate smaller. The 
central hexagon of the dorsal plates of the shell is smaller than in 
G. clavipes, and for this reason the difference between the central 
