M. Serres on Glyptodon ornatus. 435 



carapace — namely, the persistence of its natural relations with 

 the pelvic ring. 



Besides the pelvis, a fragment of the dorsal column was found 

 in its interior, but not in place. This fragment will be the subjcet 

 of a second note (p. 438), in which I propose to examine the other 

 bones which appear to me to be referable to Glyptodon ornatus, 

 and which present remarkable differences from the same organs 

 in G. clavipes. 



Anatomists are not yet agreed as to the number of vertebra? 

 which must be regarded as constituting the sacrum in the 

 Glyptodons. With Huxley, I refer to this bone the two verte- 

 brae with large transverse apophyses, united by their extremities 

 to each other and to the ischium, which limit the pelvic cavity 

 behind. Huxley calls them coccygeal vertebra of the sacrum. 

 There is no doubt that the first should be referred to the mass 

 of the sacrum ; as to the second, it has with the former such 

 connexions and such a community of relations (especially in a 

 gigantic species which I shall hereafter have occasion to bring 

 before the Academy), that it seems difficult to separate it from 

 the same group. In Glyptodon ornatus these two vertebra; ap- 

 pear to me to be the tenth and eleventh, counting as the first 

 the vertebra of which the lateral expansion forms the sacral 

 crest. 



In our specimen the iliac crests and bones, as also the cotyloid 

 cavity, present nothing particularly remarkable. 



The rami of the pubis have not been preserved. 



Behind the cotyloid cavities originate the ischia, which are 

 quite different here from the oblique and fan-like ischia of G. 

 clavipes. These ischia are directed straight backwards, only 

 diverging a little. With the sacral crests in front and the two 

 coccygeal vertebra; of the sacrum behind, they bound a nearly 

 quadrangular cavity, over which the narrow region of the sacrum 

 is thrown like a high-arched bridge. 



The ischium has the form of a triangular lamina placed in a 

 vertical plane. The apex of the triangle is at the cotyloid cavity 

 in front, the base at the carapace behind. This base, or posterior 

 margin of the ischium, is free below. Above it is cut off some- 

 what obliquely, to adapt it to the convexity of the carapace, 

 which rests upon it. The upper margin is thick, and regularly 

 concave ; the lower margin is more irregular. Near the cotyloid 

 cavity it presents a concavity, a portion of the orifice of the 

 obturator foramen. Beyond this it was united with the ramus 

 of the pubis, now destroyed. Further on it forms a lozenge- 

 shaped synarthrodia! surface, bristling with highly developed 

 osseous rugosities, which give attachment, during life, to a 

 powerful interarticular ligament. Behind this rugose surface, 



<M)tt 



