At the northern end of the Coahuila platform, the thinned Comanchean sequence consists of the newly named Sixshooter group of carbonate formations underlain by the newly named Yearwood formation. The Sixshooter group consists, in descending order, of the Buda limestone, the newly named Boracho limestone composed of the newly named San Martine and Levinson members, and the Finlay limestone at the base. Beneath the Finlay is the Cox sandstone, and beneath the Cox, the Yearwood formation, which consists of an upper limestone member previously called Rustler (Permian) and a basal conglomeratic sandstone member that rests unconformably on Permian formations. The Buda and Boracho are biostratigraphically correlative with the Washita group of central Texas; similarly, the basal part of the Levinson member and all the Finlay limestone are correlative with Fredericksburg formations. Whether any part of the Cox sandstone is contemporaneous with the Trinity group is speculative. The Yearwood is probably a Trinity, though possibly a Fredericksburg, correlative.