282 MAMMALIA. 



The earliest armadillos already mentioned as occurring in 

 the Pyrotherium Formation of Patagonia are apparently in- 

 termediate in many respects between the Glyptodontidae and 

 Dasypoda of more modern date. So far as can be determined 

 from fragmentary specimens the bony dermal scutes were not 

 externally sculptured, and they seem to have been arranged in 

 well-defined transverse rows, which were to a great extent 

 movable and might easily have undergone modification either 

 into the rigid carapace of the Glyptodonts or the familiar 

 ringed shield of the surviving armadillos. Peltephilus is the 

 strangest of these early forms, known only by imperfect 

 skeletons both from the Pyrotherium and Santa Cruz For- 

 mations. Propalceohoplophorus is another less imperfectly 

 known genus from the latter formation. The genera com- 

 prising the gigantic species of Pliocene and Pleistocene age 

 are numerous, but Glyptodon and Dcedicurus may be cited as 

 illustrating their principal features. 



Peltephilus. The skull in this genus is comparatively short and 

 broad, depressed in the rostral region, and with a strong sagittal crest 

 behind. The zygomatic arch is complete, though slender, and the part 

 of the squamosal bearing the articular facette for the mandible is 

 segmented off by a persistent suture as a small distinct element 

 (apparently identifiable with the quadrate of reptiles and birds). The 

 orbit is large and not completely separated from the temporal fossa. 

 The lachrymals are much extended on the face, but the lachrymal 

 canal opens within the orbit. The nasals are short, and the prernaxilla 

 is fused with the maxilla on each side. The posterior nares are far 

 back, and the pterygoids seem to have entered the secondary palate. 

 The mandibular rami are fused together at the rounded symphysis. 

 The teeth are all simple, have a chevron-shaped section, overlap one 

 another and wear obliquely. There are seven pairs above and below, 

 and they form a continuous series from the front backwards. The 

 axis and two or three following vertebra are fused together. The 

 scapula exhibits a well-defined coracoid process, marked off by a per- 

 sistent suture. The humerus exhibits an entepicondylar foramen, and 

 is shaped remarkably like the corresponding bone of the existing 

 Monotremes. The olecranon process of the ulna is longer and more 

 robust than usual in the armadillos. The epiphyses of the long bones 

 remain separate apparently until old age. The head bears two pairs 

 of horn-shaped scutes. The armour of the trunk and tail consists of 

 transverse series of bony plates loosely apposed, sometimes slightly 



