Published online by Cambridge University Press: 14 July 2015
Amphissites insignis Croneis and Thurman, 1939, is a readily identifiable ostracode species because of the unique configuration of carinae and ridges on the surface of the valves. The species had adapted to both shale and limestone environments of deposition, has a wide geographic distribution in the United States (Alabama, Arkansas, Illinois, Montana, Nevada, Tennessee, and Texas), and is confined to the uppermost part of the Chesterian Series (foraminiferal zones 18 and 19). The description of this species is amended and specimens are illustrated for the first time from Nevada, Montana, Arkansas, and Tennessee, indicating that the species is a biostratigraphic indicator of the uppermost part of the Chesterian sedimentary sequence. Ontogenetic development of A. insignis is reconstructed. A. sp. 1 (Late Mississippian) and A. sp. 2 (Early Pennsylvanian) are illustrated in open nomenclature.