Not drawn to scale (W 102°03ʹ00ʺ--W 94°35ʹ00ʺ/N 40°00ʹ00ʺ--N 36°59ʹ00ʺ).
Designated "SM 10" or "Special Map 10" from the Survey's "Catalogue of Publications." Includes ill. Shows eras, periods, epochs, estimated length in years, and also gives a brief description of each category. EMS copy inserted in envelope (31 x 23 cm.).