116 PROCEEDINGS OF THE GEOLOGICAL society. [Noy. 3, | 
nification of the minor but well-marked deviations of the true molars 
from those of Anthracotherium. The corresponding premolars in 
that genus present a sudden change of form and simplification of 
structure, as compared with the true molars (see fig. 9, p 4, p 3) ; 
and herein we may discern the closer affinity of Anthracotherium 
with Cheropotamus. Hyopotamus on the other hand resembles Hy- 
racotherium*, the fourth premolar of which presents externally the 
same number of lobes (two) as the true molars, and is simplified only 
by the suppression of a cusp on the inner side of the crown and its 
smaller size. With regard to the third premolar of Hyopotamus, it 
is only in the Dichodon that we find its elongated quinquelobate cha- 
racter repeated ; and it appears to me, therefore, that we have in this 
new genus discovered by Lady Hastings a most interesting annectent 
form, that, whilst it is in some measure intermediate between Hyra- 
cotherium and Dichodon, lmks both with the typical Anthracotheria. 
The close agreement of the molar (fig. 1) of Hyopotamus bovinus 
with the true molars of the smaller species, Hyop. vectianus, might 
reasonably lead to the inference that the same conformity would ex- 
tend to the premolar teeth ; but I refrain from too confidently antici- 
pating the results of subsequent discoveries of the now unknown 
parts of its dentition. It will be observed that the fourth premolar 
in the lower jaw (Pl. VIII. figs. 1, 2, 3, p 4) does not repeat the corre- 
sponding degree of complexity of the one in the upper jaw (Pl. VII. 
fig. 6, p 4), nor the third premolar the trilobate exterior division of 
the crown which we find in the lower molar of the Dichodon (see 
Pl. IV. fig. 3). 
The last two molars in the lower jaw (Pl. VII. figs. 1-3) have, 
however, the same antero-posterior extent as the corresponding teeth 
from the upper jaw of Hyopotamus bovinus, of which the most per- 
fect specimen (m 3) is figured in Pl. VII. figs. 1-5. A fragment of 
the lower jaw of the Hyop. vectianus, with the penultimate and last 
molars much-worn, shows the same correspondence between those 
teeth and the upper molars, m 2 & m 3, in figs. 6 & 7. Pl. VII.; and 
these lower molars agree so closely in structure with their homo- 
logues in the larger species (Pl. VIII. fig. 1, m2 & m 3), as to render 
a figure of them unnecessary. 
The less-instructive and determinative specimens of teeth discovered 
in the same deposit and locality as those above described, consist of 
one small two-fanged premolar tooth (Pl. VII. figs. 10 & 11), one 
thick-rooted but small-crowned canine (fig. 12), and five single-fanged 
teeth resembling the upper incisor of the great Anthracothere figured 
by Cuvier in pl. 80. fig. 6 (tom. cit.), and somewhat like those teeth 
which M. de Blainville has represented, by analogy, as the three in- 
cisors of the upper jaw in the Anthracotherium from Digom. One 
of the single-fanged teeth (Pl. VII. figs. 20, 21), with a portion of its 
cylindrical fang, is too large for any of the incisive or canine sockets 
of the under jaw above described: it may, therefore, be an incisor of 
the upper jaw of the same species. The crown is of an oval shape, 
with an obtuse summit, convex on the outer side, concave on the 
* British Fossil Mammalia, fig. 166. p. 422. 
