Marine Neogene fossil ostracod assemblages that show some degree of provinciality include those from the Louisiana subsurface, the Florida panhandle, North and South Carolina, Virginia, Maryland, and southern California. Nonmarine Pleistocene fossil ostracod assemblages from Illinois, Ohio, Kansas, Minnesota, Utah, Idaho, and Nevada, and Miocene and Pliocene assemblages from Nevada and Idaho also are represented to some extent by restricted species.

One of the main problems in the analysis of the assemblages is determination of the limiting effects of environmental factors on the species having restricted distribution versus other less tangible limiting factors. Comparisons of the fossil distributions with those of living representatives are helpful.

As an example of provincial restriction of marine Neogene Ostracoda not obviously controlled by facies, the Atlantic Coast of the United States is typified by certain species of Murrayina and Hulingsina, whereas rocks of similar age are typified (1) in the Caribbean by Ambocythere, (2) in east Africa and the Mediterranean by Chrysocythere, and (3) in Germany perhaps by Urocythereis and Kuiperiana.

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