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THE ARKANSAS COAL MEASURES.
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sular India and Afghanistan. Brazil probably belongs to this type, but is to a certain extent transitional.

The Itaitúba fauna.—A comparison of the Upper Carboniferous fauna of Itaitúba, Brazil, as described in part by Professor O. A. Derby,[1] shows that of 27 species of Brachiopoda, 12 are identical with American forms, although most of these are cosmopolitan. The genus Strophalosia is common in these beds, and as Professor Derby[2] says, the species shows affinity with the Permian. Many of the new species described by Professor Derby are closely related to the European forms. Waagen[3] says that the beds of Itaitúba are of the same age as the Middle Productus limestone of India, that is of the Permo-Carboniferous transition beds. The Brazilian Strophalosia is closely related to Australian species, indicating a closer connection with the Australian or southern Carboniferous region than with the Pacific province. Hence we infer that the Brazilian deposits may after all belong to the Upper Coal Measures, and that the difference between them and the northern Upper Coal Measures may be geographic instead of geologic.

Classification and Age of the Arkansas Coal Measures.

Provisional classification.—For the sake of convenience, the Coal Measures of Arkansas have been provisionally classified by the Survey as Upper or Productive, and Lower or Barren Coal Measures. This division is not based on any paleontologic or stratigraphic break, but merely on the occurrence or non-occurrence of coal.

The divisions that are recognized in Pennsylvania could not be recognized in Arkansas, but the strata of the two regions are correlated as far as possible with the scanty data now at hand.

The Lower Coal Measures.—Of the age of the Lower Coal Measures we have only stratigraphic evidence, their position above the limestone of the Lower Carboniferous, and below the coal-bearing beds of the Lower Coal Measures being unmistakable.

  1. ↑ Bulletin Cornell University, Vol. I., No. 2.
  2. ↑ Op. cit., p. 60.
  3. ↑ Salt Range Fossils, "Geological Results," p. 207.
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