The relations of the Taylor and Navarro formations from Collin County to Travis County are briefly described and graphically shown in the accompanying map and diagram. The Pecan Gap tongue of the Annona chalk is shown to extend into, instead of above the top of, the Taylor marl as far south as Rockwall County. The Wolfe City sand member of the Taylor is recognized as far south as Hill County, and marl of uppermost Taylor age is shown to overlie the Pecan Gap and its equivalent, the Marlin chalk. Three new members of the Taylor are recognized, the Marlin chalk of Falls and Limestone counties, the Lott chalk of Falls and Bell counties, and the Durango sand of McLennan and Falls counties. The base of the Navarro is placed at the base of the zone of Exogyra cancellata, which s shown to correspond with the base of a sandy marl from Kaufman County to Milam County and to be a probable unconformity at least as far south as Falls County. The upper Navarro rests unconformably on the lower Navarro and cuts it from the section south of Milam County.