AESlNOlTllEIilUM. 
43 
because its surfaces agree exactly with those of the radius and ulna of that animal and 
also with those of the scaphoid just described. The proximal surface of the bone 
is divided into two articular facets by an antero-posterior ridge. The smaller 
(postaxial) surface (w.) is for the ulna: it is very slightly convex in front and gently 
concave behind : its outline is roughly semicircular, the diameter of the circle being 
represented by the straight postaxial border, beneath which there is a very narrow 
facet for union with the upper edge of the cuneiform. The rest of the proximal 
surface (r.) articulates with that part of the radial head that is not received by the 
scaphoid ; it is roughly triangular and is concave posteriorly and internally, but convex 
in front. The inner (preaxial) face of the bone bears two surfaces (sc., scJ) for union 
with the scaphoid : one of these (sc.) along the upper border is long and narrow, while 
the other (-sc.') on the lower side is shorter and broader, and the two are separated by 
a deep groove. There is also a similar groove on the outer face, separating the 
upper and lower facets for the cuneiform. The distal surface (wic/i!/.), which is triangular 
in form, is gently convex from before backwards and articulates almost entirely with 
the magnum, but there is some evidence that near its antero-external angle it slightly 
overlapped the trapezoid (tr . '?). 
This bone differs from the lunar of Elephas to a considerable extent, mainly on 
account of the larger portion of its upper surface that articulates with the ulna. In 
Elephas the ulnar facet is quite small and is confined to the anterior half of the 
bone, looking much more outwards than upwards, so that very little of the weight 
transmitted to the foot through the ulna is borne by the lunar. 
The cuneiform (text-fig. 22) is, on the whole, much like that of Elephas, but its 
articulation with the ulna (ul.) is larger, extending farther outwards, and this surface 
is gently convex internally, but concave externally, with a raised outer angle. The 
surface for the pisiform (pi.) is nearer the inner (preaxial) side of the posterior face 
of the bone than in Elephas. It is nearly quadrate in outline, and its upper edge 
joins the posterior border of the ulnar surface : in Elephas this surface is triangular. 
Fostero-externally the lower edge of the bone is produced downwards and 
backwards into a strong hook-like process. Tlie distal articular surface is very 
gently convex from before backwards and concave from side to side ; externally it 
extends outwards for a considerable distance on the ventral face of the process just 
described. A narrow strip of this surface occupying its inner (preaxial) side is 
marked off from the rest by a very slight groove : this seems to have overlapped and 
articulated with the magnum, as mentioned above in the general remarks on the 
carpus. The remainder of the surface articulated with the unciform. On the inner 
(lunar) side of the bone there are two facets for union with the lunar (/.) — a 
broader one along the upper edge and a narrower one along the lower, which projects 
considerably beyond the upper, from which it is separated by a groove. 
The pisiform (text-fig. 22, pi.) is tongue-shaped. Its free end is rounded and 
G 2 
