PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
535 
backward, broader transversely, than that of the front lobe. A low and short ridge of 
enamel (h) closes both outer and inner ends of the intervening transverse valley. The 
length or vertical extent of crown between the end of the valley and the division into 
fangs is 5 lines on the inner side and 4 lines on the outer side of the tooth. The middle 
of the hind surface of the hind lobe swells out ; and as both outer and inner ends of the 
hind basal ridge (g) bend up the corresponding parts of the hind lobe, its hind surface 
shows two shallow depressions divided by the above-named rising : in these depressions 
the reticulo-punctate character of the enamel is most strongly marked. The hind basal 
ridge is thicker than the front one (f), and thickest at its middle ; its enamelled margin 
is irregular, it rises higher than, and seems to overlap, the front basal ridge of the fol- 
lowing tooth. The cement upon the exposed part of the crown of d 4, between its ena- 
melled lobes and implanted fangs, is thick. The fangs are two in number, broadest 
transversely, slightly divergent, canaliculate on the contiguous sides. 
In the jaw of an older Biprotodon the second molar (Plate XL. tig. 4, d 4) shows both 
lobes abraded to their common base, exposing the osteo-dentine (o) obliterating the 
cavity of the fang. A small part of the enamel of the front basal ridge (f) shows its 
position as blended with the front lobe. The line of enamel of the worn hind surface 
of the hind lobe (b) forms an open angle, of which the apex shows the end of the pro- 
minence joining the middle of the hind basal ridge (g), and dividing the remnants of 
the pair of depressions between that ridge and the hind lobe. The fore-and-aft extent 
of the worn surface of this molar is 1 inch 6^ lines ; that of the base of the crown is 
1 inch 8 lines ; the breadth of the hind part of the worn surface is 1 inch. The alveolar 
border rises into an angle between the origins of the fangs. 
In Plate XL. tig. 2 shows the working-surface of the crown of d 4, of rather smaller 
size than those above described, and probably from a young female Biprotodon. The 
summit of the anterior lobe is so far worn as to expose a transverse curved line of 
dentine, concave forward, beginning to expand where attrition has reached the promi- 
nent part of the hind surface of the lobe. The summit of the posterior lobe ( b ) has 
just been touched. The proportions of the basal ridges (f, g) are well shown. The 
reticulo-punctate character of the enamel is well marked. This tooth was from the 
freshwater deposits of the Province of Victoria, near Melbourne. The outer side view 
of this tooth is given in figure 1. 
From the same locality I received the third molar (m 1) of the same Biprotodon 
(Plate XL. figs. 5 & 6) : its almost untouched lobes are more compressed than in the Tapir 
and Dinothere, and their lamelliform summits rise higher beyond their basal connexions 
than in the Kangaroo ; the median connecting ridge which extends between the two 
transverse eminences longitudinally, or in the axis of the jaw in the molars of the 
Kangaroo (ib. fig. 14), is very feebly indicated by the outswelling, shown in figs. 
3 & 7, at the back of lobe a, in the Biprotodon. The anteriorly concave curve of the 
summits of the transverse lobes, in fig. 6, is more regular, equable, and greater than 
in the Tapir (fig. 15), the Dinothere, or the Kangaroo. The two fangs, the contiguous 
mdccclxx. 4 d 
