år 
the remaining teeth grow more specialised chiefly in the hindermost 
part of the jaw, in order to serve the newer purpose of mastication 
better. As to the further development of the various forms he 
essentially has adopted Osborn's view. 
In Fleischmann: "Die Grundform der Backenzåhnen”, 1891, 
we meet with opposition to Osborn's theory. He does not find 
this theory sufficiently proved and especially he thinks Osborn's 
homologising of the upper and lower tooth-cusps doubtful. The 
fact is that you often get the impression that the upper and lower 
mammalian teeth correspond with one another in inverted position, 
i, &. the outer border with the inner, the anterior end with the 
posterior etc. If this is taken as a general law, the paracone will 
be homologous with the metaconid etc. If a primitive molar, e. g. 
that of Dasyurus, is examined, one will observe that the upper 
molar has a triangular grinding surface, composed of one greater 
posterior outer triangle and two smaller anterior quadrangles, one at 
the inner and the other at the outer side, all separated by ridges. 
Fleischmann proposes the names -macromere (posterior outer tri- 
angle), micromere (anterior outer quadrangle) and entomere 
(inner quadrangle) and the whole tooth is called trimerous. 
When looking at the lower molar we observe that it entirely wants 
the entomere (bimerous), and here the macromere is situated 
anterior to the micromere. Each of the three main parts of a tooth 
is supported by a fang. — The single cusps are only to be indi- 
cated by letters, the same letter being used for the homologous 
Parts above and below. From the trimerous tooth the teeth of the 
tarnivores, the insectivores, the bats and the lemurs can easily be 
derived, In the herbivorous animals the teeth usually are more 
Complicated through the development of a metamere on the distal 
border of the entomere, Very often the macro- and micromere 
are reduced so that their outer border has disappeared (corresponding 
to the vanishing of cusps: 1—2—3 [Winge]); the lower molars 
keep their form for the longest time. — As shown by Cope the 
teeth of the herbivores are transformed so much that the original 
