EDENTATA OF THE SANTA CRUZ BEDS. 113 



while the remaining ones are coossified together and with the first lumbar 

 to form the "dorsal tube," while the remaining lumbars and the sacrals 

 unite in the " lumbo-sacral tube." The caudal vertebrae are characteristi- 

 cally glyptodont in form. 



9. The scapula is relatively high and narrow and finds its nearest ana- 

 logue, among the Pampean genera, in Sclerocalyptus. In the pelvis, the 

 ilium and ischium meet at a more open angle than do those of the later 

 genera and the obturator foramen is larger. 



10. The hind-limb is much longer than the fore-limb, which produces 

 the extreme curvature of the vertebral column. Proportionately, the limb- 

 bones are much more elongate and slender than in the subsequent genera, 

 Sclerocalyptus approximating the Santa Cruz type in this respect more 

 closely than do the other Pampean forms. 



11. The humerus is quite slender and retains well-developed deltoid 

 and supinator ridges and large epicondylar foramen, its whole appearance 

 resembling that of the large Santa Cruz armadillos, and the same resem- 

 blance is found in the radius, while the ulna is very broad and has a more 

 typically glyptodont shape, though it is far less massive than in the 

 Pampean genera. The manus is very incompletely known, but the parts 

 that have been recovered indicate its likeness to that of Sclerocalyptus, 

 except that the claws are narrower and more pointed and that, probably, 

 the pollex was retained. 



12. The femur is very much more slender than in the later glyptodonts 

 and is much more armadillo-like ; the third trochanter arises but little below 

 the middle of the shaft, instead of just above the external condyle. The 

 tibia and fibula are completely fused at both proximal and distal ends, 

 and are relatively short, laterally compressed and very thick antero- 

 posteriorly ; except for their much greater slenderness, they resemble 

 those of the later glyptodonts in form. The pes is pentadactyl, broad 

 and very short, not unlike that of Sclerocalyptus in its proportions ; the 

 ungual phalanges are thoroughly hoof-like. 



13. Of the three families into which it is usual to divide the glyptodonts, 

 only two, the Glyptodontidce and Dwdicuridce, have so far been found in 

 the Santa Cruz fauna, although it is probable that the Sclerocalyptidce had 

 already come into existence at that time. 



14. The Santa Cruz glyptodonts are decidedly more primitive than 

 those of later epochs, and to a certain extent they bridge over the gap be- 



