EDENTATA OF THE SANTA CRUZ BEDS. 



I I I 



postero-external lobe by a vertical groove ; in Eucinepeltus this division 

 is very feebly indicated, while in Propalceohophphorus it is quite distinct, 

 in Cochlops strongly marked and in Metopotoxus still more so, and this 

 genus is still further distinguished by the unusual complexity of -. The 

 later glyptodonts are characterized by the complexity of the anterior teeth, 

 by the absence of any division of the postero-external lobe (except in - of 

 Sclerocalyptus] and by the enlargement of the outer lobes, which makes 

 the grinding surface much more symmetrical. Still another difference be- 



FlG. II. 



Skulls of glyptodonts, top view, x^ ; a. Glyptodon asper (after Burmeister). b. Propalaohop- 



lophorus australis ; c. Eucinepeltus complicates. 



tween the Santa Cruz and the later genera is in the form of the median 

 ridge of harder dentine on the masticating surface, which is much more 

 complexly ramified in the Pampean types. 



7. The skull is quite completely known in nearly all of the genera, but 

 only in Propalcsohoplophorus has any considerable part of the skeleton 

 been recovered. However, there is no reason to suppose that noteworthy 

 differences in skeletal structure existed between the various genera. As 

 compared with the Pampean genera, the Santa Cruz glyptodonts have a 

 type of skull which is characterized by the elongate rostrum, the low jaws, 



