28 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. 



have disappeared, the arch continues as a prominent ridge, with a wedge- 

 shaped top, and is recognizable even on the ? seventeenth caudal. Distinct 

 neural spines occur only on the first and second vertebrae. The transverse 

 processes diminish gradually in length throughout the series, but are distinct 

 even on the ? seventeenth. Vertebrae one to four have similar transverse 

 processes, except that on the fourth the ends are vertically expanded and 

 decurved in a way that does not occur in any other vertebra. At the fifth 

 caudal a comparatively sudden change occurs, the transverse processes 

 becoming broader and curving forward, and at the distal end the breadth 

 of the process exceeds the length of the centrum, an arrangement which 

 continues to the twelfth. These broad, wing-like processes are very char- 

 acteristic of the present genus and are quite different from those in the 

 corresponding region of Tatu, in which the breadth of the processes is 

 much less than the length of the centrum, and consequently the intervals 

 between the successive processes are much greater than in the fossil. 



Seven chevron-bones are associated with the same individual, none of 

 them, unfortunately, in position ; they are triangular in shape and perfor- 

 ated by a canal for the caudal artery and vein. Anteriorly, the chevron- 

 bones are narrow in the fore-and-aft dimension and, when viewed from the 

 end, have the shape of a nearly equilateral triangle, with a large perfora- 

 tion ; posteriorly, they become shorter dorso-ventrally, broader and more 

 canoe-shaped, while the canal is reduced. 



Of ribs, two are preserved. The first rib is of the usual armadillo pat- 

 tern ; it is short, but extremely broad and plate-like, with concave inner, 

 straight outer and convex ventral border. The other ribs are relatively 

 broad and in shape resemble those of Dasypus, rather than those of Tatit. 



Of the sternum, the posterior segment, or xiphisternum, has been re- 

 covered ; it is quite broad in front, tapering posteriorly, and its anterior 

 end has two facets for the sternal ribs, separated by a distinct notch. 



Appcndicular Skeleton. The scapula (Plate IV, fig. 3), is quite peculiar 

 and differs from that of any other Santa Cruz genus, as well as from that 

 of any existing armadillo with which I have been able to compare it, being 

 remarkably small, both in height and in the breadth of the dorsal part. 

 On the whole, the nearest resemblance is with the shoulder-blade of Tatn, 

 though there are many differences. The neck is broad, more so than in 

 Tatn, and there is no coraco-scapular notch, a marked distinction from 

 Dasypus ; the coracoid border is concave for about half its length and then 



