"O. clarki" is found in Upper "Olenellus"-zone of California (Bristol Mountain, near Cadiz, on the Santa Fé Railroad, 100 miles East of Barstow, Mohave Desert, probably Latham Shale; Latham Shale – treated as the "Bristolia"-zonule – Marble Mountains, ½ mile East of Cadiz, and at the Southern end of the Marble Mountains, near Chambless in the Mohave Desert portion of San Bernardino County, as well as from the Latham Shale, near Summit Springs on the West side of the Providence Mountains, San Bernardino County. In California also from the Carrara Formation, Funeral Mountains, Resting Spring Range, Eagle mountain, Grapevine Mountains, Salt Spring Hills); and in Nevada (Nevada Test Site, Desert Range).