EDENTATA OF THE SANTA CRUZ BEDS. 123 



PI. XXXI). The ascending ramus is very broad and arises very far for- 

 ward from the outer side of the horizontal portion, so that in side view 

 the last two teeth are concealed from sight ; it has a much smaller vertical 

 extension than in Glyptodon and the condyle is not elevated nearly so 

 high above the level of the teeth. The condyle itself is of a shape like 

 that of the latter and presents obliquely forward in a similar way, but is 

 much less massive, while the sigmoid notch is considerably deeper. 

 Coronoid and angle are quite alike in the two genera, but the ventral 

 border of the jaw rises much more suddenly to the ascending ramus in the 

 Pampean type. 



The cranial foramina present a number of interesting points. The 

 infraorbital foramen is large and is double, at least in some individuals, 

 the smaller opening being above and external to the larger (Plates XXIII, 

 fig. 4 ; XXVII, 2). The optic foramen is remarkably small and is con- 

 tinued forward for some distance as a groove beneath the overhanging 

 ledge of the frontal. Close behind the optic foramen is the foramen 

 lacerum anterius and beneath the latter is a large opening, probably vas- 

 cular, into the maxillary. The foramen rotundum is placed considerably 

 behind the foramen lacerum anterius and is closely followed by the fora- 

 men ovale ; this is an important difference from Glyptodon, in which, 

 according to Huxley ('65), the foramina rotundum and lacerum anterius 

 have a common opening. The loss of the tympanics has destroyed the 

 foramen lacerum medium and eustachian canal in all of the specimens that 

 I have examined, but the foramen lacerum posterius is still visible. The 

 condylar foramen is large and is placed so near to the condyle as to be 

 partly concealed in the ventral view, and the stylo-mastoid foramen is a 

 conspicuous opening through the mastoid portion of the periotic. 



Vertebral Column, Ribs and Stermim (Plates XXII, XXV). Ameghino 

 states ('94, 170) that in the young animal the vertebrae are all separate. 

 In the adult, however, the concentration is almost as complete as in the 

 Pampean genera. The neck is very short, intermediate in its proportions 

 between that of Sclerocalyptus and that of Glyptodon. The atlas, which is 

 free, is shaped much as in the former and in the larger armadillos, being 

 broad, but very short, with the anterior cotyles projecting well in front of 

 the neural arch, which is conspicuously perforated by the foramina for the 

 first pair of spinal nerves ; the neural spine is almost obsolete and the in- 

 ferior arch narrow and very slender ; as in Proeutatus, the vertebrarterial 



