Neohipparion sp. from the Flaxville Gravel of Sheridan County, northern Montana, compares well with late Hemphillian species of Neohipparion in height of crown, shape of protocone, and development of pli caballin. A late Hemphillian age conflicts with the Barstovian or Clarendonian age suggested by Collier and Thorn's original evidence. The part of the Flaxville Gravel considered differs greatly in age from the nearby Wood Mountain Gravel of Saskatchewan, although it may be comparable in age with the Hand Hills Gravel of Alberta.

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