. Bulletins of American paleontology. MoLLUSKS Past and Present: Brewster-Wingard et al. 227. Text-figure 15.—'"Blow-out" areas at Bob Allen mudbank, February 1999. Sharp transition between lush Tlialassia beds and areas of gelatinous calcareous mud are visible. Photo courtesy of Thomas Scott, Florida Geological Survey. and Acteocina in some samples from Pass Key and Russell Bank may be indicative of lowered salinities. Samples from piston cores RB19B and PK37, and the upper portion of BA6A. are primarily grouped in cluster K (Text-figs. 11 and 14). This is equivalent to the Brachido
. Bulletins of American paleontology. MoLLUSKS Past and Present: Brewster-Wingard et al. 227. Text-figure 15.—'"Blow-out" areas at Bob Allen mudbank, February 1999. Sharp transition between lush Tlialassia beds and areas of gelatinous calcareous mud are visible. Photo courtesy of Thomas Scott, Florida Geological Survey. and Acteocina in some samples from Pass Key and Russell Bank may be indicative of lowered salinities. Samples from piston cores RB19B and PK37, and the upper portion of BA6A. are primarily grouped in cluster K (Text-figs. 11 and 14). This is equivalent to the Brachidoiites assemblage identified in the modem presence-absence data analysis. Modern push cores and vegetation samples from the corresponding sites (12, 13, and 20) also fall into cluster K in the com- bined analysis. These sites occur within eastern and east-central Florida Bay. and they can be characterized as shallow mud banks with sub-aquatic vegetation and macro-benthic algae present. Salinities have ranged from 17-33 ppt at site 20, 19-37 ppt at site 12 and 27-41 ppt at site 13 during our periods of observation. Typically, either the Brachidoiites or Pteria longisqiia- mosa assemblages have dominated at these sites in the modern presence-absence data (Text-fig. 3). The prev- alence of the Brachidoiites assemblage down-core for PK37 and RB19B, and down to approximately 54cm in BA6A. indicates that the general environmental conditions were the same in the past. The common species in cluster K correspond to the characteristic species identified by Turney and Perkins (1972) for their interior subenvironment. Samples from the lower portion of piston core BA6A are dominated by the Transennella assemblage that defines cluster L. This assemblage also is seen in portions of RB19B (30 cm and 118 cm) and PK37 (6 cm). This is an infaunal assemblage and so it was not identified in the modern presence-absence analysis. Transennella sp. are present in the modem push core samples, but they
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