Includes generally cliff-forming, thin- to thick-bedded limestone. These rocks are mainly shallow water subtidal, intertidal, and supratidal deposits formed on a broad inner carbonate shelf (Stewart, 1980). The Devils Gate Limestone and Guilmette Formation in northern Nevada are the principal units, and the Sultan Limestone is included from the southern part of the State. Unit is overlain (usually disconformably) by the Pilot Shale of unit MDcl except in southernmost Nevada where it is overlain by Mississippian carbonate (Mc). It depositionally overlies Middle and Lower Devonian unit Dcd. In a few places, such as southern Nevada and parts of Eureka County, regional mapping did not distinguish the Upper and Middle Devonian section from the Lower Devonian section, and all of the Devonian is included in unit Dc. Rocks mapped as the Simonson Dolomite would fit into this depositional sequence (sequences 9 and 10 of Cook and Corboy, 2004), but they are not differentiated from the underlying dolomites in White Pine or Elko Counties, so they are all included in unit Dcd here, not unit Dc. This unit crops out in Clark, Elko, Eureka, Lander, Lincoln, Nye, and White Pine Counties.