Discovery of Upper Ordovician strata in the Llano uplift of central Texas is here reported. These rocks, named the Burnam limestone, are considered to be correlative with some part of the Richmond group, because of the presence in them of Halysites (Catenipora), Streptelasma rusticum, Austinella, Mcewanella raymondi, Strophomena aff. S. nutans, Rhombotrypa, and other fossils. Closest correlation is believed to be with the Maquoketa formation and equivalents in the Mississippi Valley, but affinities are also indicated with the type Fernvale formation of Tennessee, the so-called Fernvale limestone of Missouri, Arkansas, and Oklahoma, and possibly with some part of the upper Montoya limestone and upper Maravillas chert of West Texas.

The only outcrops of the Burnam limestone known at present are preserved in a collapse structure in southern Burnet County, Texas. This limestone is exceptionally pure, very coarse-grained, light-colored, and fossiliferous. Large and relatively solid fossils such as corals and cephalopods show evidence of breakage and wear, but smaller and normally buoyant ones such as brachiopods are not worn, although they are commonly disarticulated. Environment of deposition may have been near a wave-breaking organic reef (or reefs) or near pre-existing coral beds.

Rocks equivalent in age to the Burnam limestone are to be expected in the subsurface of north-central and West Texas, as well as in the Llanoria channel of the Ouachita trough. The growing list of relict Paleozoic formations being found around the margins of the Llano uplift indicates the probability of a more complete subsurface Paleozoic succession in Texas than was formerly supposed.