38 
TERTlAIiT VERTEBIiATA OF THE FAYtTM. 
lobe is nearly vertical and does not extend so liigh np as tlie upper end of the 
olecranon process. Of tlic two horizontal surfaces the inner [i.) is much the larger 
and is oval in outline, its antero-posterior diameter being slightly greater than the 
transverse ; it is concave in all directions. The outer (o.) is the smaller and is 
semicircular in outline, the diameter of the semicircle looking forwards and inwards 
and marking the line of union with the radius, with which the bone unites in a 
narrow vertical surface (r.5.). Immediately beneath the transverse articulation is 
Text-fig. 18. 
A X f B X 1 - qI 
Left ulna of Ay-sinoilherium zitteli : A, from front ; B, from outer side ; C, proximal end (with radius) ; 
H, distal end (witli radius). 
n«., surface for cuneiform ; e.p., external prominence ; < 7 ., groove above distal articular end ; i., inner surface 
for humerus; surface for lunar; e., outer surface for humerus; 0 /., olecranon yjrocess ; r., radius ; 
r.s., proximal surface for radius; r.s.', distal surface for radius; sc., surface for scaphoid; m., ulna. 
I nat. size. 
a deep fossa which receives the head of the radius. The shaft of the bone is 
triangular in section, the posterior angle being continuous with the hinder border 
of the olecranon process. The shaft is also curved somewhat backwards and 
inwards. Towards the distal end, which is considerably enlarged, the inner border 
