1847. | OWEN ON ENGLISH EOCENE MAMMALIA. dl 
therium. The oblique tubercle, 7, is now developed into a compressed — 
lobe or ridge; in other respects P 4 resembles P 3, but is larger. It 
is implanted by four fangs. 
The first true molar (M 1) deviates least from the Paleeotherian 
type; the worn summits of the two conical and subcrescentic outer 
lobes present the two zigzag lines of enamel which Cuvier compares 
to a double W, and the vertical ridge dividing them on the outer sur- 
face of the tooth reaches the margin of the grinding surface: the 
concavities in the outer surface bounded by the above-described ridge, 
and the anterior vertical ridge, show a slight median rising. The 
oblique ridge of the lobe 7 on the grinding surface, bemg worn, pre- 
sents a narrow tract of dentine, extending from the posterior and in- 
ternal angle of the crown to near the interspace of the two outer lobes 
0, o': it answers to “autre ligne pareille qui part du milieu de la 
ligne en W,” &c. in the Paleeotheres*. 
The summits of the tubercle p and of the antero-internal lobe (¢) 
are blended together by attrition, and show a tract of dentine parallel 
with %, but thicker and of a bilobed form; extending from the ante- 
rior and external angle to the middle of the mternal border of the 
crown. The oblique peninsular fold of enamel (e), penetrating from 
the inner side of the crown and dividmg the before-named tracts, 
doubles the extremity of the posterior tract (¢) and communicates 
with the posterior depression or fold of enamel: in equally worn 
molars of Paleotherium that fold (a) is cut off, and forms an island. 
There is a ridge at the fore-part of the base of the inner lobe p; and 
also a slight remnant of the cingulum at the entry of the fold e. 
The molar fig. 2. M 2 has had merely the summits of the highest 
lobes and ridges of the griding surface abraded; the tubercle p and 
the antero-internal lobe 7 continue distinct. The posterior boundary 
of the posterior depression is unworn. 
The last grinder, M 3, has just cut the gum, and almost corresponds 
in growth with the last upper molar of the Paleotherium medium, 
figured in the ‘Ossemens Fossiles,’ pl. 47. fig. 14; and with that 
of the Paleotherium crassum, figured in my ‘Brit. Foss. Mamm.,’ 
fig. 112. p. 319. The generic distinctions are accordingly well-dis- 
played in the comparison of the germ of the last molar of the Paloplo- 
there with those in the true Paleeotheres above-cited. The antero- 
internal lobe (2) rises quite independently between the crescentic 
lobe o and the large inner tubercle p. The posterior inner lobe 7 ex- 
tends forwards and outwards as an oblique ridge to the entering angle 
of the anterior and external crescent. The remnant of the cmgulum 
at the base of the fissure e does not rise above that part, and its com- 
munication with the basal ridge at the fore-part of the lobe p is 
interrupted. The two outer vertical channels are less deep than in 
the Palzeotheres, and the bottom of each is gently convex in both 
directions. 
Each of the true molars is implanted by four fangs, the two inner 
ones appearing to be connate, and the two posterior ones in the last 
* Ossem. Foss. iii. p. 9. 
