84 Dr. Burmelster on the Species o/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 ' NacionaP 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 

 of 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 arc 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 like 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 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. setoms), the 

 Mataco (D. conurus), and the Pichy (Z). 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. 



