434 M. Serres on Glyptodon ornatus. 



Behind, in the vicinity of the posterior emargination, the 

 inner face of the plates is, on the contrary, irregular, rugose, 

 and uneven ; nor do we find the same regularity in the distri- 

 bution of the vessels, each plate having often several nutritive 

 foramina. To all appearance this region gave attachment to 

 muscles analogous to the elevators of the tail in the Armadillo, 

 muscles which are seen to attach themselves, on the one hand, 

 to the inner face of the posterior buckler, and, on the other, to 

 the spinous apophyses of the first caudal vertebrae. 



The margins by which the plates are articulated together 

 present the asperities usual on such organs. They were united 

 by fibrous tissue. Perhaps, at the perfectly adult age to which 

 our specimen had attained, some of these articulations were ossi- 

 fied in the dorsal region ; but certainly this was not the case 

 throughout. It may be asserted that the carapace no more 

 formed a shell homogeneous and solid in all its parts, than the 

 thoracic and ihac bucklers of the Armadillo are solid and in- 

 flexible. It must have become flattened or arched a little in 

 accordance with the efibrts of the animal ; in other words, it 

 must have changed its form, certainly within narrow limits, but 

 still appreciably. 



The caudal emargination is formed by a single row of plates 

 arranged in an arc, like the stones of a bridge. 



The cephalic emargination is much more complicated in its 

 structure. It is not simply circular, but shows on the median 

 line a projection in the form of a hood, slightly prominent, but 

 massive, with its margins rounded at the expense of the outer 

 face of the carapace, sharp at the level of the inner face. 



Three difierent rows of plates assist in the formation of this 

 anterior emargination, and furnish in turn its marginal pieces. 

 The series which borders the most lateral part of the emargina- 

 tion extends, gradually diminishing, over one-thii'd of its com - 

 pass. Here it disappears. The row which was the second on 

 the sides thus becomes marginal, and disappears in its turn in 

 the same manner. There remains the third, which thus becomes 

 marginal in the middle of the notch. In other words, the row 

 which bounds the emargination in the centre alone constitutes 

 a complete arch, resting on each side upon two other arches, 

 which become less and less complete. 



All the plates in the vicinity of the anterior emargination 

 bear on their surface excavations measuring about 4 millimetres 

 in all directions ; these are rounded, with two or three Haversian 

 canals opening in their bottom. These cavities lodged the bulbs 

 of large hairs, directed forwards, which fringed the anterior 

 margin of the carapace of the animal. 



I now come to that which constitutes the great interest of this 



