74 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



curved neck, and the other ribs, both costal and sternal, are somewhat 

 more slender. 



The same is true of the sternum; the manubrium is relatively a little 

 narrower than in the recent genus and the posterior part, behind the rib- 

 facets, shorter. The xiphisternum is much more slender and less de- 

 pressed ; the median portion is more constricted and the hinder end 

 broader, thinner and more spatulate. 



Appendictilar Skeleton.- -The scapula (Plate VI, fig. 5) is, on the whole, 

 most like that of Dasypus and is smaller, especially much narrower, than 

 that of Zaedyus; the coraco-scapular notch is much shallower than in the 

 latter and even shallower than in the former, and the coracoid border 

 is slightly raised and pursues a sinuous course, meeting the suprascap- 

 ular border at nearly a right angle ; the postero-superior angle of the blade 

 is produced into a flat, sickle-shaped extension, like that of Zaedyus, 

 but very much smaller ; the spine, which has a nearly median position, 

 has a thickened and recurved free border; nothing is known of the 

 acromion. The coracoid is a long, slender, incurved hook, like that of 

 Zaedyus, but narrower. 



The humerus (Plate VI, fig. 6) closely resembles that of Zaedyus; as in 

 that genus, the bicipital groove is converted into a canal by a bony bridge, 

 which connects the tuberosities ; the deltoid ridge is immensely devel- 

 oped and ends distally in a broad, overhanging hook ; the internal epi- 

 condyle is relatively larger than in the modern genus; the trochlea, 

 which is very low and wide, has a prominent hemispherical convexity for 

 the radius. 



The ulna and radius (Plate VI, figs. 7, 8) are so like those of the recent 

 genus that no description of them is required, further than to note their 

 greater relative slenderness. 



A large part of the manus (Plate VI, fig. 9) is associated with one 

 individual of P. exilis, but lacks the radial side of the carpus, metacarpal 

 I and all of digit V. The lunar is relatively large and rests principally 

 upon the unciform. The pyramidal is short and very wide and has the 

 usual articulation with metacarpal V ; its oblique position in the carpus 

 makes the ulnar surface almost as much lateral as proximal. The mag- 

 num is very small and the unciform proportionately large. 



The metacarpals are like those of Zaedyus, except in being more slender. 

 Metacarpal II has the characteristic convex head for the trapezoid and is 



