N'OTODIAPHORIS CRASSUS 



35 



condyles there is a deep rugose pit for the plantaris muscle, 

 and on the anterior side the suprapatellar fossa is well 

 marked. The condyles are placed a trifle obliquely; the 

 internal one being shorter and with a rounded articular 

 face, the external condyle being longer, and with a flat- 

 tened articular face which slopes obliquely inward. 



Of the tibia, only the distal end is preserved. This in- 

 dicates a rather slender bone, with a shal- 

 low, fairly wide concavity for the external 

 astragular trochlea, and a narrower and 

 deeper concavity for the internal astragu- 

 lar trochlea. On the internal side of the 

 tibia there is a rugose surface for the fibula. 



An isolated lower end of a fibula indi- 

 cates a slender bone, enlarged distally 

 where it conies in contact with the tibia. 

 The fibula carries on its inner face a mod- 

 erately large facet for the external side 

 of the astragulus, and on the distal end a 

 wider one for contact with the calcaneum. 



The tarsus is compactly built, wider 

 than that of Diadiaphorus. because the 

 external digits are not as much reduced. 

 This especially shows in the greater de- 

 velopment of the cuboid and the meso- 

 cuneiform, but in other features it is similar to that of its 

 descendant. 



The astragulus is a very characteristic bone. The trochlea 

 is asymetrical. the external condyle rising higher than the 

 internal, and the median groove being wide and shallow. 

 On the nearly vertical outer face of the astragulus, there 

 is a semicircular band-like facet for the fibula. The trochea 

 extends well around the top of the bone, allowing a wide 

 movement of the foot. The neck of the astragulus is long 

 and wide, carrying a broad flattened head, with its con- 

 vex facet for the navicular, covering the entire end. On 



Distal end of left 

 tibia — i j natural size. 



