44 
TERTIARY VERTERRATA OF THE FAYOM. 
it bears on its n]i])er surface a prominent knob. The proximal end, winch is a 
little wider than the distal, is entirely occupied by an oblong facet for articulation 
with the cuneiform ; connected with the upper edge of this surface there is another 
very narrow facet extending across the whole width of the bone and marking its 
point of contact with the ulna. Connected with tlie ventral border of the cuneiform 
facet there is a rather irregular rounded surface, somewhat roughened and apparently 
resulting from the occasional contact with the upper face of the posterior process of 
the cuneiform. 
Test-fig. 22. 
Left cuneiform and pisiform of Arsinoitherium zitleJi: A, from above ; B, lunar face. 
1., facets for lunar; pi., pisiform ; ul., surface for ulna. 4 nat. size. 
The trapezium and trapezoid are not certaiidy known. 
The magnum (text-fig. 23) is quadrate in section anteriorly, but posteriorly it 
narrows considerably at least on its ventral side. 4'hc up])er surface is gently 
concave in front, but ])osteriorly is raised into a considerable convexity, the ])ostero- 
internal slope of wliicli supplied a surface for union with the scaphoid {sedj. Most 
