Four new formation names are used herein for hitherto undescribed or inadequately described rocks in the Jackson Hole region, Teton County, Wyoming: The name Harebell formation is used for a 5,000-foot succession of quartzite pebble conglomerate, olive-drab to gray sandstone, drab-colored siltstone, claystone, and shale of Late Cretaceous age unconformably overlying older Cretaceous rocks and unconformably overlain by Paleocene and younger Tertiary rocks. The name Colter formation is used for a 7,000-foot sequence of white, gray, green, and brown, water-laid basic pyroclastic conglomerate, tuff, sandstone, and claystone of middle Miocene age, unconformably overlying all older rocks and unconformably overlain by rocks of middle Pliocene age. The name Teewinot formation is used for 5,000 feet or more of white limestone, pumicite, tuff, claystone, diatomite, and conglomerate of middle Pliocene age, unconformably overlying all older rocks and unconformably overlain by strata of late Pliocene or Pleistocene age. The name Bivouac formation is used for 1,000 feet of poorly lithified conglomerate interbedded with less amounts of sandstone, siltstone, claystone, pumicite, and welded rhyolite tuff of late Pliocene or Pleistocene age, unconformably overlying rocks of middle Pliocene age, and unconformably overlain by glacial and integlacial deposits of Pleistocene age.