OSTEOLOGY OF THE HYOPOTAMIDiE. 
51 
In examining the radial side of the unciform of Hyopotamus we shall see that the 
upper lunar facet of this bone nearly meets the lower facet (Plate XXXVIII. fig. 7), the 
two being separated merely by a ridge*, while in Anoplotherium (Plate XXXVII. fig. 2, u , 
and Cuv. plate 102. fig. ii. A 5 m ) these two facets are separated by a vertical facet, 
which articulates with the neighbouring os magnum. In the Suiclce this facet is exceed- 
ingly developed, and the homologue of the lower facet hi. (Plate XXXVII. fig. 7) is 
confluent with it in such a way that both together (^-j-m, Cuviek, Oss. Foss. pi. 102. 
fig. ii. A 5) form the radial high and perpendicular border of the pig’s unciform ; at 
the upper part of this perpendicular border abuts the os magnum, at the lower the 
beak-like projection of the third metacarpal; this last projection, therefore, is more 
horizontal in Suidae, and not so oblique as in Anoplotherium and Hyopotamus. The 
posterior projection of the unciforme is tolerably broad and well developed, as is seen 
in Plate XXXVIII. fig. 7. 
Dimensions. 
Transverse breadth 
Unciform 
from Puy. 
. . 22 
Unciform 
from Hempstead (fig. 9). 
17 
Depth, antero-posterior 
. . 22i 
17 
Height ...... 
. . 17 
12 
I had already completed this description when I received unexpectedly, through the 
kindness of Mr. Davies, sen., of the British Museum, two carpal bones from the Museum 
in Cambridge. On examination both proved to be unciforms. One of them (Plate 
XXXVIII. fig. 9 & 9') corresponded very closely to our unciform from Puy, being, 
however, much smaller; it may have belonged to some of the smaller Hyopotami , 
whose metacarpals, corresponding entirely in shape with those from Puy, are often 
found at Hempstead. This small unciform is figured in Plate XXXVIII. fig. 9, front 
view, 9' the distal surface ; it is from the left side, like the corresponding one (figs. 5 & 7) 
from Puy. Its distal articular surface (Plate XXXVIII. fig. 9') has three facets — one for 
the beak-like projection of the third metacarpal, a central one for the fourth meta- 
carpal, and an outer (v.) for the metacarpal of the small or fifth digit. The posterior 
part of this small unciform is drawn out into a tolerably broad backward projection. 
The second of the two unciforms received from Cambridge was found at Hordwell ; 
it proved a most valuable addition to my materials, as, after a careful study, I arrived at 
the conclusion that it undoubtedly belonged to the large didactyle form referred by me 
to the genus Diplopus with the specific name Aymardi. Figs. 8 & 8', Plate XXXVIII. 
give a front and a distal view of this interesting bone. Comparing it with the same bone 
from Puy, or the small one from Plempstead, we are at once struck by their difference. 
The front view, in consequence of the large development of the inferior radial angle, 
presents a much squarer outline ; the inner vertical wall of the bone has become much 
* This makes the Hyopotamus unciform look exceedingly like that of a Palceotherium crassum ; but this 
similarity is only superficial, as the distal surface and the posterior beak are very different from what we see 
in Palseotheridas. 
MDCCCLXXIII. 
I 
