318 PALAOTHERIUM. 
the tooth, where it expands into a wide and deep depres- 
sion. The convex inner sides of the lobes c, ¢, are bor- 
dered near their base by a ridge. The outer surface of 
each lobe is gently hollowed out from side to side at d, d, 
the hollows being bounded by three longitudinal ridges. 
The posterior lobe is subdivided by a short and wide fis- 
sure a, which is expanded and deepened at its extremity, 
like the fissure 6. These fissures are formed by folds of 
the capsule or bag of the formative matrix of the tooth; 
and as the capsule supports the organ which forms the 
enamel, the edges of the folds of enamel so formed, are 
exposed by the wearing away of the grinding surface of 
the tooth, and beimg harder than the dentine or central 
substance of the tooth, they stand up above it like the 
exterior border of enamel surrounding the tooth. In 
specimens of fossil molar teeth of aged animals in which 
the crown has been much worn, the more shallow beginnings 
of the enamel folds are worn out, and only the deeper ter- 
minal depressions remain, forming, as in fig. 113, detached 
islands of enamel instead of the peninsulas which charac- 
terise the grinding surface of the molars of younger animals. 
It is requisite to bear in mind these changes of the pattern 
of the grinding surface of the complex molars of the Her- 
bivora in determining the nature of a fossil tooth, lest 
differences due to age should be mistaken for the dis- 
tinguishing characters of species or genera. 
I have, as yet, seen no other unequivocal relic of the 
largest species of true Paleothere. For the opportunity 
of examining the fossil figured, I am indebted to the Rey. 
T. Darwin Fox, M.A. 
