477 
THE STRUCTURE AND RELATIONSHIPS OF ANCODUS. 
form are two lacets for the lunar; the proximal one is small and confined to the 
dorsal inargjn, while the distal one occupies the whole depth of the bone. The 
unciform facet is rather small, not taking up the whole distal surface of the cunei- 
form, and is rather concave. The cuneiform of Oreodon is lower, but deeper antero- 
posteriorly than that of Ancodus, and more cubical in shape. The pisiform is not 
preserved in any of the specimens. 
The trapezium is relatively well developed ; it is narrow and compressed, but 
C£uite high and deep. In view of the comparatively large size of the pollex, it is 
somewhat surprising to find that the trapezium has but a small facet for the scaphoid, 
and articulates more extensively with the first and second metacarpals and with 
the ti’apezoid. The surface for the trapezoid is situated rather high up on the ulnar 
side of the trapezium, and below it is a small facet for the second metacarpal. The 
distal facet for me. I is narrow but deep, convex and broader in front, concave and 
contracted behind ; the distal end extends a little below the level of the trapezoid. 
The trapezium has not been found in the European species, but, as Kowalevsky 
showed, the facets on the trapezoid and me. II demonstrate its presence in these 
forms. The trapezium occurs also in the oreodonts, but its shape is known only in 
Mesoreodon and Merycochasrus^ in both of which genera the pollex has disappeared 
and the carpal is reduced to a mere nodule. 
The trapezoid is narrow, but much extended antero-posteriorly, thus reversing 
the proportions found in Mesoreodon. The proximal end bears a rounded, convex 
facet for the scaphoid and the distal end a narrow, saddle-shaped one for me. II. On 
the ulnar side is a plane surface for the magnum, which occupies the entire height 
of the bone, but only about one-half of its dorso-palmar depth. The trapezoid of 
the European species does not differ in any important respect from that of the 
American. 
The dorsal face of the magnum, exposed when all the carpal elements are in 
position, is broad and low, but toward the palmar side it rises to a considerable 
height, though not forming a well-defined, rounded head. Posteriorly the magnum 
is provided with a long, stout, and somewhat decurved hook. The scajihoid facet 
takes up most of the proximal side; it rises toward the ulnar side, wdiere its junc- 
tion with the lunar facet forms a high crest. It also rises gradually toward Ae 
palmar side, and is transversely concave throughout; there is, however, a \mry faint 
indication of a dorsal concavity and palmar convexity. The lunar facet is lateral 
rather than proximal ; in front it is narrower and nearly plane, descending almost 
to a junction with the surface for me. Ill, while behind it rises to form a broad 
convexity, which is more proximal in position, and is reflected well over upon the 
palmar side of the bone. Distally there is a large saddle-shaped surface lor me. Ill, 
as well as a narrow, plane liicet for me. II upon the radial side. 
The mamniin of Oreodon, while essentially like that of Ancodtis, has still many 
points of difference. (1) There is a distinctly developed head, and the scaphoid 
facet is very clearly divided into dorsal concavity and palmar convexity. (2) The 
lunar facet has a more completely lateral position, and does not broaden out behind 
