MEGACEROPS TYLERI 455 



The astragalus presents a beautiful hour-glass-shaped, astragalo- 

 tibial facet, bearing on its outer face a clearly defined fibula facet. 

 The range of flexion and extension in the tibio-tarsal joint is con- 

 siderable. Distally two facets are indicated, that for the navicular 

 being by far the larger, and somewhat flattened, and with a small, 

 prominent, downwardly projecting process, which effectually limits 

 any fore-and-aft motion. A prominent ridge divides the two facets, 

 that for the cuboid being an elongated triangle, first convex, and 

 then concave from before backward. 



The navicular is very flat and presents two distal facets, that for 

 the ectocuneiform being the larger, and somewhat triangular in shape, 

 while that of the mesocuneiform is semilunar, the line of demarcation 

 between the two being almost straight. 



The cuboid has a thickness equal to that of the navicular and 

 ectocuneiform combined, and exhibits proximally two contiguous 

 facets, the lesser for the calcaneum and the greater for the astragalus. 

 Distally there are two facets, the external, the area of which is about 

 four times the greater, being for metatarsal 4. This is somewhat 

 saddle-shaped, while the other, that of metatarsal 3, is nearly fiat. 



The ectocuneiform is absent in the right pes, though present in the 

 left, being replaced in the former by that of another individual. It 

 articulates distally with metatarsals 3 and 2, though the latter articula- 

 tion almost fades out anteriorly, broadening as one goes to the rear. 

 This is markedly different from most titanothere feet which the author 

 has seen, in which a wide line of contact is indicated on the face of 

 the tarsus. There is, however, no possibility of contact between the 

 mesocuneiform and metatarsal 3, as the former articulates distally 

 with metatarsal 2 only. 



The whole pes is remarkably rigid when compared with the manus, 

 as there is little indication of any intertarsal movement, none between 

 the tarsus and the median metatarsal, and no lateral and but little 

 fore-and-aft play between the tarsus and the lateral metatarsals. 

 The principal dimensions of the pes are : 



Width of astragalar facet - 0105 



Length of calcaneum ------- . 208 



Width of the distal row of tarsals ------. 140 



Height, astragalus to proximal end of the third metatarsal . 108 

 Length of the third metatarsal 205 



