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THE JOURNAL OF GEOLOGY.

New York and farther southwest. It should not be applied to cover the three divisions of the Upper Devonian, because as a time indicator it is inappropriate, as just stated; and as a formation name it has already a use, and should not be used in two senses; and, thirdly, even if used in the more comprehensive sense, it is inapplicable because the Portage and Chemung are not represented, at least only imperfectly, in the geological area named Catskill.

The Catskill is a distinct and well defined geological formation, but it is not a period or an epoch, nor does it represent any particular period of geological time. The classification of the Upper Devonian deposits is a very difficult matter when it is attempted to make a continuous series of the formations of New York alone. As I have previously shown, the succession of faunas in the sections of New York rocks at distances of not over fifty miles apart make plain this fact. At the Cayuga lake meridian, the section is Hamilton, terminating with Tully limestone and Genesee shale, then the Ithaca group, which has first a Portage fauna, then the Ithaca fauna, third, the Portage fauna again, and finally Chemung capped by Catskill and Carboniferous. A little further east of the Chenango valley, it is Hamilton; then a fauna intermediate between Hamilton and Ithaca (but no Tully or Genesee); then the Oneonta, a brackish and fresh water fauna; then the late Ithaca fauna, still with Hamilton types in it; no Portage fauna, but Chemung fauna following the upper Ithaca fauna.[1]

In this faunal succession there is a clear indication of the age of the Oneonta sandstones. It is clearly in the midst of the rocks characterized by the Ithaca fauna. As I have shown in the paper referred to,[2] the marine Brachiopod faunas occupying the place between the Hamilton and the Chemung faunas in Central New York, of which the Ithaca is the best known, are modified successors of the Hamilton, or Mesodevonian fauna, and the Oneonta group, with its fresh and brackish water fauna is in the

  1. ↑ Williams: The Classification of the Upper Devonian.Proc. Am. Assoc. Adv. Sci., Vol. XXXIV., p. 225, 1886.
  2. ↑ Proc. A. A. A. S., XXXIV., 1885, pp. 222-3.
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