58 
DR. W. KOWALEVSKY ON THE 
has also a small facet, to which this rudiment was attached (Cuvier does not mention 
this, as he treats both Dichobune and Xiphodon very briefly). This additional facet 
for the rudiment of the fifth metatarsal is to be seen in He Blainville ( Anopl . 
plate v.) ; it certainly existed in Dichobune and Cainotherium , as both have a completely 
developed fifth digit in the pes and manus. 
Now, looking at the distal surface of the cuboid of Hyopotamus (Plate XXXVIII. 
fig. 10), we clearly perceive two large articular facets (iv. & v.) nearly in the same mutual 
relation as in Hippopotamus ; the two facets are numbered iv. and v. in correspondence 
with the metatarsals they support ; and their outline corresponds very nearly with the 
proximal surfaces of these two metatarsals (Plate XXXVIII. fig. 1, iv., v.). The inner 
border of the facet iv. is convex, the outer (near the ridge that separates the two facets) 
concave ; and corresponding to this the inner border of the fourth metatarsal is con- 
cave, and the outer convex, to fit the cuboid. The facet v. is a little convex and tri- 
angular ; and the metatarsal v. is shaped in a corresponding manner. 
Besides the cuboid figured from Buy, I had a smaller cuboid from Hempstead, with 
two facets on its distal surface for the fourth and fifth metatarsals, and another from 
the same locality much larger than the Buy specimen, but corresponding closely with it; 
unhappily this last large specimen is much rolled, and the articular facets are not quite 
distinct. 
If we compare with the cuboid just described the same bone from a nearly complete 
foot found at Hordwell (Plate XXXVIII. figs. 3, 4, and, distal view, 11) belonging to the 
Diplopus, or the two-toed form of this family, we shall see important differences which 
must clear away any possible doubt as to the number of digits in the genus Diplopus. 
The front view of the cuboid, fig. 3, shows it to be a little narrower than the same bone 
in its smaller but four-toed congener ; and this is especially the case if we compare the 
posterior parts of both bones, as seen in figs. 10 and 11. On the inner wall, the middle 
anterior rising which enters into the interval between the navicular and third cuneiform 
is more distinctly developed, as seen in fig. 3 ; the rising, with a facet for the distal surface 
of the navicular, on the posterior border of the cuboid, is not so thick and not produced 
so much inwards as in Hyopotamus , but repeats entirely the arrangement seen in the Hog. 
The external surface is more hog-like in appearance, and differs from the same 
surface of Hyopotamus by the presence of a deep sulcus (fig. 11) between the distal 
articular facet and the posterior prolongation (fig. 1 \,f.my), which, in this genus, is 
produced much lower down than in Hyopotamus. Instead of the broad transverse ridge 
seen on the posterior surface of the cuboid in the Hyopotamus (fig. 10, tr), the cuboid of 
the two-toed Diplopus has this ridge prolonged downwards in a beak-like process quite 
of the same shape as in the common Hog (fig. 4, b.cb ). This posterior beak descends 
lower down than the distal articular surface of the cuboid, and exhibits on its inner side an 
elongated facet (fig. 11, f.my) by which this beak articulates with a corresponding cuboid 
facet on the outer side of the posterior prolongation of the fourth metatarsal (fig.4", iv. 
cb.f). This articulation is observable, though imperfectly, in fig. 4, where the beak of 
the cuboid (b.cb) is seen descending on the other side of the fourth metatarsal. In my 
