Three General Principles for a System of Classification of Fossil Conchostracans

Three principles are formulated and illustrated for use in the classi-fication of fossil conchostracans: (1) Exclusion-this principle establishes the inadequacy of the available evidence for the assumption of a one-to-one relationship between fossil and modern conchostracans; (2) Effectiveness-this principle pertains to the limited utility of a single morphological character as a taxonomic device and recognizes that the final test of adequacy is in its actual use in discriminating between fossil carapaces; (3) Total Morphological Pattern-this principle indicates the conditions under which a single morphological character as a taxonomic device can have extended applicatio