These ancient opossums have been separated generically from Didelphys (in its widest sense) on account of certain differences in the relative sizes of the lower premolars, but as nearly the whole of the species have been formed .on lower jaws, of which some hundreds have been found, it is impossible to judge how far these differences are correlated with other dental or osteological characters.
Kitson's work in Tasmania shows that there also the glacial beds may be correlated with the lower or Greta Coal Measures of New South Wales.
It flickered on for her, and she correlated their coordinates with two touches.
At Bajo de Velis, in San Luis, the plants belong to the " Glossopteris flora," which is so widely spread in South Africa, India and Australia, and the beds are correlated with the Karharbari series of India (Permian or Permo-Carboniferous).
The reduction of the tentacles in all these forms may be correlated with their mode of life, and especially with living in a constant current of water, which brings foodparticles always from one direction and renders a complete whorl or circle of tentacles unnecessary.