EDENTATA OF THE SANTA CRUZ BEDS. 131 



head and but slightly invading the articular surface ; the great trochanter 

 is large, rising far above the head, but is not nearly so broad as in the 

 Pampean types ; the digital fossa is completely obsolete ; the second tro- 

 chanter is not very prominent, but extends as a roughened ridge for some 

 distance down the inner side of the shaft ; the third trochanter is much 

 more like that of one of the large Santa Cruz armadillos than one of the 

 later glyptodonts, and its position is intermediate between these two ex- 

 tremes ; it is a prominent, antroverted hook, situated below the middle of 

 the shaft and therefore more distal than in the armadillos, much more 

 proximal than in the Pampean glyptodonts. The shaft is proximal ly 

 broad, much compressed antero-posteriorly and has a nearly flat posterior 

 surface ; from this proximal expansion the shaft contracts downward, 

 becoming cylindrical above the third trochanter, and thickening and widen- 

 ing moderately at the distal end ; this elongate and slender shaft is in very 

 striking contrast to the extremely massive character of the bone in the 

 great Pampean genera. The rotular groove is broad and quite deep, 

 with raised and distinct internal and very low external border ; a small, 

 but well-defined suprapatellar fossa is sometimes, but not always present; 

 the condyles are small and of unequal size, the inner one projecting more 

 both posteriorly and distally, but there is no such difference as in Sclero- 

 calyptus ; the inner condyle is regularly rounded, while the outer one rises 

 into a blunt, but prominent ridge. 



The patella does not closely resemble that of any of the Pampean 

 genera; it is rather small, and though quite thick, is much less so than 

 in Sclerocalyptus or Panochthtts, while it is not so flattened as in Glyptodon, 

 nor has it the external process seen in the latter. 



The leg-bones (Plate XXVI, fig. 7) are coossified at the two ends, 

 widely separate elsewhere ; they have considerable resemblance to those of 

 Proeutatus, especially in front view, but are relatively shorter and heavier. 

 As compared with the femur, the tibia has nearly the same relative length 

 as in Sclerocalyptus and is much more elongate than in Glyptodon ; the 

 proximal end is broad and thick and has a bifid spine produced by the 

 elevated mesial borders of the widely separated condyles, of which the 

 internal is larger and more concave and stands at a much lower level, 

 while the external one is slightly convex and has a faintly marked groove 

 for the ridge on the outer femoral condyle. Except at the distal end, the 

 shaft is much compressed laterally and plate-like, very thick antero-pos- 



