The Perissodactyla. 987 
-show this clearly. The lunar bone has extended outwards so 
as to rest on the outside bone of the second row (unciform) in 
part, as well as the one on which it properly rests (magnum), 
_ But the scaphoid has not slipped outwards so as to rest on the 
magnum of the second row. That continues to rest on its proper 
successors below, the trapezoides and the trapezium, the latter 
taking half the burden. This structure (Fig. 2) is absolutely 
intermediate between that of the Taxeopoda (Fig. 1) and that of 
the Diplarthra (Fig. 3), and I imagine that all ungulates, in pass- 
ing from the taxeopodous to the diplarthrous stages, traversed 
Ee magnum, while the lunar did not pass outwards beyond the 
— dmits 
_, > of the magnum. No such type has been found. On the 
: other hand, I have shown that the Oredontidæ* have pushed the 
2 transposition of the bones of the first carpal row to such an ex- 
ee 
we that the magnum has gotten entirely under the scaphoid, 
ne the unciform supports the lunar completely. Thus the 
mating position, with its useful mechanical consequence, has 
been lost to this group, the effect produced being exactly t 
E _* Proceeds. Amer, Philosoph. Society, 1884, pp- 503-9 
e XXL—No, II, 67 
