AESINOITHERITJM. 



51 



there is on either side of the bone a prominent tuberosity {i.t,, o.t.). The posterior 

 surface of the shaft immediately above the condyles is slightly concave from side 

 to side, the concavity being bordered by ridges running upwards and inwards from the 

 tuberosities. The lower end of the bone is much narrower than the upper end. 



The femur of Uintatherium differs in the following points : — (1) it is not so 

 much compressed from before backwards, and at the same time it is considerably 

 narrowed from side to side near its middle ; (2) there is a small but prominent 

 lesser trochanter ; (3) the hinder surface of the great trochanter is hollowed by a 

 digital fossa ; (4) the distal articular end is relatively larger. 



The femur of Mephas differs from that just described in the following points : — 

 (1) the neck is much longer ; (2) the great trochanter does not rise nearly so high 

 and its posterior face is excavated by a deep digital fossa; (3) the shaft is not 

 compressed to anything like the same degree, and its posterior face is not so much 

 flattened ; (4) the distal articulation is relatively larger. 



Text-fig. 29. 

 A, B. 



Bight patella of Arsinoiiherium zitteli : A, from inner side ; B, from articular face. 

 i., inner surface for femur ; o., outer surface for femur ; pr., distal process. | nat. size. 



The patella (text-fig. 29) is much like that of Uintatherium. The surface for 

 the outer condyle (o.) of the femur is smaller than that for the inner (i.) ; both are 

 gently concave from above downwards, and very nearly flat from side to side. Below 

 the articular surface the bone is produced downwards into a blunt triangular 

 process (pf.). The anterior face as usual consists of a greatly swollen and roughened 

 mass of bone. 



The tibia (text-fig. 30) is a short stout bone considerably expanded towards 

 the articulations. The facets for the condyles of the femur are deeply concave. The 

 inner («'.) is much the larger and is oval in outline, the long axis being antero- 

 posterior. The outer (o.) is smaller and more nearly circular, and its long axis 

 is from within outwards : in front of it and to the outer side of the anterior 



h2 



