It is desirable to stabilize the concept and nomenclature of biotic provinces in biostratigraphy. Recent marine provinces are regions of fairly uniform climatic regimes, within which communities maintain rather consistent specific associations, biotope for biotope. These provinces may be as large as major climatic belts, or as small as regions among which the effects of environmental differences, excluding climatic differences, remain smaller than the effects of climatic differences alone. Provinces are commonly separated by topographic irregularities which produce hydrographic peculiarities that emphasize the climatic change. The geologic record of a province is clearly a biostratigraphic unit according to the Code of Stratigraphic Nomenclature and formal nomenclatorial recommendations should be established. The geologic records generated by biogeographic patterns of individual taxa also are worthy of status as biostratigraphic units. Since geographic ranges of taxa change in time, it is especially useful to recognize the differences in horizontal distributions of taxa during successive parts of their existence. These units have the properties of time-stratigraphic as well as biostratigraphic units, and represent horizontal slices of range zones. A simple nomenclature that reflects these properties should be recommended.