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. tuber culatus, 

 which M. Nodot has erected into a separate genus — Schisto- 

 pleurum^. The difi'erent 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 arc consequently ignorant. M. Nodot 

 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, forming between the posterior 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 as in 

 the rings described. These ellipses are very different in pattern 



* [Now well known in England by Mv. Gregory's excellent restoration. 

 — Transl.j 



