50 
DK. W. KOWALEVSKY ON THE 
certainly must have approached that of Anoplotherium. I pass on to the most important 
of the bones of the second row — the unciform. 
Happily we are very well off as to this bone, there being some excellently preserved 
specimens from Puy. The shape of this bone and its connexion with the adjoining parts 
present considerable interest. 
The unciform of Hyopotamus (Plate XXXVIII. fig. 5 u, fig. 7) presents some like- 
ness to the same bone of Anoplotherium and also of Sus ; but nevertheless its differences 
from both, especially the last, are numerous. Comparing the front view of fig. 5 and 
the view of the distal surface (fig. 7) with the corresponding aspects of the unciform 
of Anoplotherium in Cuvier (plate 102, fig. ii. A 2 & 3), we shall see that they present 
many features in common in both genera ; I shall add that in Cuvier’s figure (A 3), 
the letter k corresponds with our III., the letter h with our IV., and the letter i with 
our V.* 
Looking at the bone from above or in front (Plate XXXVIII. fig. 5, u), we see that 
its radial facet articulates with the outer face of the lunar bone, while its ulnar facet 
is occupied by the pyramidal. The facet for the pyramidal is larger than that for 
the lunar, both in Hyopotamus and Anopl 'other him (Plate XXXVIII. fig. 5, u, and 
Plate XXXVII. fig. 2, u), while it is just the reverse in Sus, where the lunar facet of 
the unciform is much larger than the pyramidal facet. Both facets are divided by a 
pretty prominent ridge. The whole bone is relatively higher than in Anoplotherium , 
in correspondence with the lighter and more elegant stature of the Hyopotamus. 
The distal articular surface is shown in Plate XXXVIII. fig. 7, and may be compared 
with the same aspect of the unciform of Anoplotherium (Cuv. pi. 102. fig. ii. A 3). 
We find on our bone the same facets; only their relative development is different. 
III. is the radial inferior facet, giving articulation to the prolonged beak of the third 
metacarpal (k in Cuvier) ; IV. is the middle, principal, or central facet, articulating with 
the fourth metacarpal ( h in Cuvier) ; outside from it is seen another smaller, facet (V.) 
for the lateral or fifth digit (Cuv. i)\ ; and we see just the same in the Suidae, which 
have a complete fifth digit, and in Anoplotherium , where there is only a rudiment of 
it. In Hyopotamus and Hippopotamus (Plate XXXVII. fig. 1), however, owing to the 
greater development of the fifth metacarpal, this facet is not pressed so much backwards 
and upwards as in the pigs ; in the living Hippopotamus it is entirely on the same 
level with the facet for the fourth metacarpal (Plate XXXVII. fig. 1, u). 
* In Cuvier the bone is turned in an opposite direction, though it is from the same side, the left. 
t Cuvier (Oss. Eoss. 4th ed. vol. v. p. 425), describing this facet i as supporting the rudiment of the fifth 
toe, adds, “On n’en trouve l’analogue ni dans le bceuf, ni dans le cochon, ni dans le Tapir, &c.” It is certainly 
not found in Bos, as the Ox has no rudiment of the fifth toe ; but it is always to be found in the Suidae as well as 
in the Tapir, both these having a completely developed fifth toe, which is articulated to the homologue of this 
facet. In all Mammalia, without exception, the unciform supports the fourth and fifth metacarpals ; therefore 
in all mammals both these facets are homologous, whether they support completely developed toes or only 
rudiments of such, as in Anoplotherium. 
