94 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. 



wider, but are recognizable on the last vertebra preserved. Chevron-bones 

 were present throughout. 



The ribs are quite different from those of any other Santa Cruz genus. 

 The first rib, though much broader than the others, is not nearly so ex- 

 panded and plate-like as in the preceding genera, and presents more 

 laterally, less directly forward than in them ; as in the armadillos gener- 

 ally, it has no sternal rib, but articulates directly with the manubrium. 

 The succeeding ribs are remarkable for their thickness, being much less 

 compressed and flattened than in the other contemporary genera. Well 

 ossified sternal ribs are present, though nothing can yet be determined 

 regarding the number of them. 



The sternum has an elongate manubrium, which is relatively narrower 

 than in the preceding genera, being especially slender behind the expan- 

 sion for the attachment of the first pair of ribs, which is very large and 

 prominent ; dorsally, the bone is concave and on the ventral side is a 

 prominent median keel. Either this keel differs much in the various species, 

 or else it increases greatly with age, for in the young individual of P. 

 strepens it does not agree with Ameghino's account, who describes it as 

 " une forte crte mediane tranchante et d'un developpement enorme com- 

 parable seulement au brechet des oiseaux" ('940, 177). A segment of 

 the mesosternum is trihedral, with sharp ventral edge. 



Appendicular Skeleton. Limbs and feet are of a typically armadillo- 

 like character, though almost every bone has its peculiarities. A fragment 

 of the distal end of the scapula exhibits a very broad neck, with hardly an 

 indication of the coraco-scapular notch and with glenoid border raised 

 into a prominent spine-like ridge ; the coracoid is large and long remains 

 separate from the scapula. The humerus differs but little from that of 

 Proeutatiis; the external tuberosity is very large, the internal very small 

 and both are connected by a narrow bridge of bone, which converts the 

 bicipital groove into a foramen, as in Prozaedius (fide Ameghino) ; the 

 deltoid ridge is very large, though hardly so greatly developed as in Pro- 

 eutatus, and much the same may be said of the supinator ridge, while the 

 internal epicondyle is even larger ; the trochlea is very low proximo-distally 

 and has an inconspicuous convexity for the head of the radius. 



The ulna (Plate XVI, fig. 9) differs little from that of the preceding 

 genera, being short, heavy, and compressed, with very long olecranon ; the 

 sigmoid notch is short and rather shallow, but much extended transversely 



