. Bulletins of American paleontology. t-strongly skewedmarine faunas summarized in Table 2. In the Para-starte Subfacies the first three taxa make up fully 50%-of the taxa found, while the 86 least common taxa fallin the last 1% of the assemblage. In the Tricolia Bio-facies, there are 10 taxa in the first 50% of the assem-blage and only 74 in the last 1 % although there are 69more taxa in the Tricolia Biofacies than in the Para-starte Subfacies. Another way of expressing this difference can beseen by comparing the scales on the two X-axes. Inthe Parastarte Subfacies the first vertical line on
. Bulletins of American paleontology. t-strongly skewedmarine faunas summarized in Table 2. In the Para-starte Subfacies the first three taxa make up fully 50%-of the taxa found, while the 86 least common taxa fallin the last 1% of the assemblage. In the Tricolia Bio-facies, there are 10 taxa in the first 50% of the assem-blage and only 74 in the last 1 % although there are 69more taxa in the Tricolia Biofacies than in the Para-starte Subfacies. Another way of expressing this difference can beseen by comparing the scales on the two X-axes. Inthe Parastarte Subfacies the first vertical line on theleft side of the graph (Text-fig. 2) represents ofthe taxa and the fourth vertical grid line is at the Tricolia Biofacies graph (Text-fig. 3) the left-hand grid represents only of the taxa and the99% level is reached only at the seventh vertical gridline. The BiofaciesDominance of each fauna by a few taxa is the char-acteristic that makes it possible to identify biofacies in MoLLusK Shells in Florida Bay: Shaw. Text-figure 2.—Structure of Northern Parusiarle Subfacies samples Text-figure 3.—Structure of Tricolia Biofacies sample the field. The skewed faunal structure makes it possi-ble to identify a small number of Key Taxa to discrim-inate each biofacies. If the faunas were not so stronglyskewed we would need to use many more taxa. The marine molluscan biofacies defined below arebased on analyses of surface samples. The same as-semblages are present in the core samples, but weviewed core data as problems to be interpreted ratherthan part of our definitions. The only exception to thisrule was the use of a single core sample in definingthe quasimarine Everglades Biofacies. We did not gointo The Everglades to sample this biofacies on thesurface so most of our samples of it are from cores. Our general order of presentation is similar to thatused by Turney {in Turney and Perkins, 1972), startingin the north at The Everglades and moving outwardtoward the
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