10 



PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 



generally from the jugal, but sometimes from the zygomatic process of 

 the maxillary also. 



The cervical vertebrae closely resemble those of the modern armadillos, 

 one or two vertebrae coalescing with the axis. The trunk is short and in 

 those genera in which the number is known does not contain more than 

 eleven thoracic and four lumbar vertebrae ; in the lumbar and the posterior 

 part of the thoracic regions, the vertebrae have the same complex mode 

 of articulation, by means of accessory zygapophyses, as is found in recent 

 genera. The sacrum is long and always has an extensive union with the 



FIG. 3. 



Skulls of Santa Cruz armadillos, x f . a, Stegotherium tcssclatum ; b, Prozaedius exilis ; c, 

 Proeutatus lagena ; d, mandible of P. cenophorus, crown view of right ramus. 



ischia. The tail varies considerably in the different genera ; it is usually 

 quite elongated, but in some of the genera, as Proeutatus, it is of only 

 moderate length, though very heavy ; in Stegotherium the caudal vertebrae 

 are remarkable for the great development of their transverse processes. 

 The ribs, both costal and sternal, and the sternum differ in no important 

 respect from those of the recent armadillos. 



The shoulder-girdle is practically the same as in the existing genera, 

 but the humerus is noteworthy for the great size and prominence of the 

 deltoid ridge, and the epicondylar foramen is always present. The ulna 

 has a very large olecranon, which in most of the species terminates proxi- 



