2OO 



PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. 



the last-named genus and its fibular border is far less concave ; the proxi- 

 mal portion of the shaft is subtrihedral and the distal part is broad and 

 antero-posteriorly compressed, but for most of its length is of irregularly 

 oval section ; the cnemial process is very inconspicuous. The distal end 

 is much like that of Nothrotherium, but the conspicuous process, grooved 

 by a tendinal sulcus, which projects from the inner side (see Plate XXXIII, 

 fig. 3#), is more prominent than in that genus or in Megalonyx, and the 

 inner malleolus is less reduced than in the latter. The astragalar surface 

 has two shallow facets divided by a low intercondylar ridge, which, on the 

 dorsal border becomes a tongue-like process ; the external astragalar facet 

 is continuous with that for the distal end of the fibula ; the latter surface 

 presents distally rather than laterally, as is also true of both the Pleisto- 

 cene genera. 



The fibula (Plate XXXIII, fig. 3, 30), though short and stout, is rela- 

 tively much longer and more slender proportionally than in Mylodon; 

 the proximal end is thick and club-like and bears an elongate, narrow 

 facet for the tibia; the shaft is irregularly cylindrical and the distal end 

 much enlarged and very massive. 



MEASUREMENTS. 



Femur, length from head 212 



" " " great trochanter. .. .218 

 " width of proximal end 084 



Femur, width of distal end over tuber- 

 osities 076 



Femur, width of rotular groove 026 



" " over condyles 066 



Patella, length 041 



" width 037 



Tibia, length 163 



" width of proximal end 1 062 



" thickness of proximal end 057 



Tibia, width of shaft in middle 02 1 



" thickness of shaft in middle 028 



" width of distal end 055 



" thickness of distal end 028 



Fibula, length 155 



" width of proximal end 020 



" thickness of proximal end 029 



" width of shaft in middle oio 



" thickness of shaft in middle 014 



" width of distal end 023 



" thickness of distal end 030 



The pes (Plate XXXII, fig. 4) belongs to the type of Megalonyx and 

 Nothrotherium, both of which it resembles. The astragalus is much like 

 that of the former genus, but somewhat longer and narrower ; the trochlea 

 is much more deeply grooved and is quite distinctly divided into inner 

 and outer condyles, of which the internal one is much larger both in the 

 proximo-distal and dorso-plantar diameters ; at the distal end the trochlea 



1 Reduced by lateral crushing. 



