1847. | OWEN ON ENGLISH EOCENE MAMMALIA. 41 
mere rudiment of the anterior basal ridge. The summits and ‘sharp 
borders of each of the six lobes have been slightly abraded, and the 
dentine exposed, but along a mere lmear tract in each lobe. 
The penultimate premolar (P 3) retains only the hinder transverse 
pair of lobes; the middle and anterior lobes are single, subcom- 
pressed, convex on both inner and outer sides, which meet at trenchant 
and slightly-worn edges, trending away from before and behind the 
summit. The posterior cusp is present at the back part of the base 
of the inner and posterior lobe, but not at the fore part; the cusp 
behind the preceding is also wanting ; there is a trace of the posterior 
basal ridge, and an obtuse belt at the inner side of the base of the 
anterior lobe which terminates in a feeble promimence anteriorly. 
This tooth has two long slightly diverging fangs. 
The antepenultimate or second premolar (P 2) is three-lobed, the 
mid-lobe being the longest, the hind-lobe the thickest: this has a 
well-defined vertical ridge, with a notch behind it on its imner side ; 
it is simply convex externally: the mid-lobe is less deeply indented 
on the back part of its mner side, is convex on the rest of that side, 
and on the outer side ; the fore and hind sloping borders are trenchant : 
the front lobe is concave on the inner side, which has an obtuse border 
at its base: the antero-posterior extent of the crown of this tooth is 
thrice the vertical extent. It is implanted by two fangs. 
_ The anterior premolar (P 1) is situated directly above the back part 
of the symphysis of the jaw: its crown is more compressed and 
trenchant than the second, and the anterior and posterior lobes are re- 
duced to accessory basal cusps of the middle lobe: they are all so com- 
pressed as to produce an undulating trenchant summit, rising to a 
higher poit at the middle: there is no indent dividing the anterior 
from the posterior lobe on the outer side; but their distinction is in- 
dicated by a depression on the mner side. This tooth is implanted by 
two fangs. 
The left ramus of the lower jaw of the Dichodon includes a great 
portion of the symphysis, with the sockets of the canine and of two 
incisors, with a part of that of the anterior incisor, 11. A detached 
single-fanged tooth which fits the socket of the cane (C), and 
one of the incisors equally fitting the vacant socket of the third of 
this series (I 3), accompanied this specimen. In both rami the 
canine precedes the premolar without any interval, and is as directly 
preceded by the third incisor, so that the whole series of teeth is 
uninterrupted, as in the extinct genera Dichobunes, Anoplotherium, 
and Nesodon. 
The canine has a low but long trenchant crown, not rising into a 
point, resembling in its harmless character that of the Anoplotheriide : 
its outer side is gently convex ; its inner side has two indentations. 
The incisor has a smaller but more quadrate and truncate trenchant 
crown ; it is also gently convex externally, and with two concavities 
internally. 
A gubernacular orifice behind the rising crown of the second true 
molar indicated the concealed alveolus of the third molar, which I ex- 
posed in the ramus of the jaw (fig. 2, M3). The matrix had either 
not begun to be calcified, or in such detached portions of the summits 
