378 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. 



is an indication of the digital fossa ; the shaft is thicker and the condyles 

 are much larger. 



In Notoryctes the femur is quite different from that of either of the other 

 genera ; the head is large and presents directly inward ; the proximal end 

 is much widened by the expansion of the great trochanter, which encloses 

 a broad, shallow fossa on the anterior face of the bone, but there is no 

 digital fossa or third trochanter ; the femoral shaft is short and straight. 



The tibia of Necrolestes is slender and elongate, though a little shorter 

 than the femur. The proximal condyles are faintly marked and are sepa- 

 rated by a very shallow groove ; there is no tibial spine. The anterior 

 border of the proximal end of the tibia is raised into a crest, which makes 

 this end decidedly concave in the antero-posterior direction, but there is 

 no distinct cnemial crest. The shaft is slender and has a lateral sigmoid 

 curvature, while toward the distal end it broadens slightly. The fibula is 

 closely applied to the tibia, but does not coalesce with it at any point ; its 

 proximal and distal ends are broad and thick and the shaft is slender, but 

 not filiform. 



In Chrysochloris the leg bones are coossified ; the proximal end of the 

 tibia has not the vertical crest which is characteristic of Necrolestes, but 

 possesses a feebly marked cnemial process, which gives to this region of 

 the shaft a more trihedral shape. In Notoryctes the leg bones are very 

 peculiar ; the tibia has an immense cnemial crest, which runs nearly the 

 whole length of the shaft and to which the relatively enormous patella is 

 attached ; the shaft is short and straight, much compressed laterally, but 

 made exceedingly thick antero-posteriorly by the great cnemial process. 

 The fibula is free and is in contact with the tibia only at the two extrem- 

 ities ; it also has the proximal end much expanded antero-posteriorly, 

 while the shaft is stout and has a thickened distal end. 



Of the pes in Necrolestes only the calcaneum, astragalus and cuboid are 

 represented. The calcaneum has a rather short and slender tuber, which 

 is tapered toward the free end and is so curved as to be convex externally 

 and concave internally, thus differing from both of the modern genera, in 

 which the tuber is longer, stouter and quite straight. The astragalus has 

 a neck which is directed strongly toward the mesial side of the foot, end- 

 ing in a very small rounded head. The cuboid is very small, but of a 

 shape not unlike that seen in Chrysochloris, which, however, much exceeds 

 it in every dimension, especially in the proximo-distal length. So much 



