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Latitudinal patterns of diversity (number of species) vary widely for 13 families and one genus comprising about 50% of California coastal fishes. Clustering based on the presence or absence of species in bays, or at intervals of latitude in California (32-420 N), was used to produce dendrograms of 224 bay-occurring species, of 280 non bay-occurring species and of approximately 500 species in toto; these in turn served to identify three distributional regions in California waters: (1) southern (32-330 N); (2) central (approximately 34-360 N); and (3) northern (approximately 37-420 N). Mean latitudinal dissimilarity was greatest (53%) for the bay dendrogram and least (10%) for the non-bay dendrogram. Although the Point Conception area (34.50 N) was the most distinct faunal boundary in all three dendrograms, analysis of southern and northern end points of ranges for the 500 coastal species showed that Point Conception is more of a boundary for southern species than for northern ones. An ordination two-way table produced by principal coordinates analysis was consistent with the results of the end point analysis and illustrated the high degree to which latitude accounts for the distribution patterns. Greater 'activity' with regard to range terminations occurs in southern California and Baja California than in central and northern California and is in agreement with the pattern of decreasing diversity with increasing latitude in California. Faunal discontinuities in the eastern North Pacific, based on distributions of California fishes, are similar, with few exceptions, to those recognized in studies of benthic molluscs and other marine invertebrates, and apparently reflect marine climate patterns. The results of the analysis emphasize the complex and dynamic character of the Californial coastal fish fauna.