M. Serres on Glyptodon ornatus. 433 



carapaces figured by Owen and Nodot. The latter have a very 

 distinct convexity from one extremity to the other. Ours, on 

 on the contrary, presents a well-marked sort of constriction at 

 about the second third of the length of the body. Hence a rule 

 tangent to the line of the back may touch it at two points, and 

 subtend an arc (which, however, is very flat) between the scapular 

 and iliac regions. Behind this constriction the carapace, through- 

 out the iliac region, presents the form of the segment of a 

 sphere. 



All the osteites forming it have a common characteristic type, 

 which, however, is more or less altered in certain regions — 

 namely, in front, behind, and on the margins. These modifica- 

 tions, on which I cannot dwell here, are nevertheless useful to 

 know. They might lead to error in specific determinations made 

 from too small fragments. This common type evidently corre- 

 sponds with the fragment of a carapace figured by Owen under 

 the name of Glyptodon ornatus, and reproduced less successfully 

 by Nodot. 



Here and there we perceive little shapeless plates filling the 

 vacant spaces left by the regular design of their neighbours, 

 which does not accommodate itself well to the spherical surface 

 of the carapace. But this aberration is a normal fact, — the 

 dermal bones of the Edentata belonging, like the squamose 

 bones of the cranium, to that variety of the primary osseous 

 organs which originate without preexistent cartilages, and which, 

 in consequence of their spontaneous mode of origin and develop- 

 ment, always present great variations of number and configura- 

 tion. 



The inner face of the plates generally presents a remarkable 

 uniformity. At the points where they were in connexion with 

 the bones of the muscular skeleton the union was effected by 

 fibrous tissue, and not, as Burmeister gives us to understand, 

 by cartilaginous tissue. Indeed in the Armadillo it is likewise 

 fibrous tissue that unites the extremities of the ischia to the 

 processes of the posterior buckler to which they apply them- 

 selves — a very dense fibrous tissue, with fibres of variable but 

 generally considerable diameter, attaining as much as 0*007 mill. 

 These fibres are arranged in slightly undulated and imperfectly 

 limited bundles. 



Throughout the anterior region of the carapace the inner face 

 of the plates is perfectly smooth. They all uniformly present a 

 nutritive foramen in their centre, analogous to that which is 

 seen on the inner face of the plates of the Armadillo, into which 

 an arterial branch of considerable volume always penetrates. It 

 is evident that in this region the carapace reposed upon a thick 

 cushion of adipose tissue. 



Ann. fy Mag. N. Hist. Ser. 3. Vol. xvi. 29 



