Ear bones of Nototheria and allied animals

If we pass in review the osteology of the ear bones of the Kangaroo, the Wombat, the Native Bear, etc., and then turn to the Nototneria, we get an interesting series of departures from a common type, which latter we may assume began by manifesting a fairly normal development of the bones, in the region of the ear. Just what that ancient type was need not at present detain us, our work being rather that of showing how the bones have developed, dwindled, coalesced, and otherwise altered, as the several groups of marsupials, above named, followed their special lines of evolution. In so doing, are we to regard each group as being a law unto itself expressed, once and for all, or did the several changes become analogues of those passed through by other creatures (not of necessity marsupial) in other parts of the world? Although perfectly aware of the fact that this subject is not popular with modern biologists, we think that work along these lines is worth attempting, and will eventually be found useful.