. Bulletins of American paleontology. be distinguished at two levels. Afield sample containing 40% or more of caecids, re-gardless of the species, is part of the Reef Tract Bio-facies. In the laboratory, the critical clue is the abruptincrease in numbers of C. cornucopiae. It is not im-portant elsewhere. SUBSIDIARY TAXA: A number of larger, but lesscommon taxa are more numerous on the reef tract thanin Florida Bay. There are new kinds of pelecypods(chamids and pectens) plus those large and spectaculargastropod shells so sought after by collectors, likeSiromhus and Cassis. Transennella cubanian
. Bulletins of American paleontology. be distinguished at two levels. Afield sample containing 40% or more of caecids, re-gardless of the species, is part of the Reef Tract Bio-facies. In the laboratory, the critical clue is the abruptincrease in numbers of C. cornucopiae. It is not im-portant elsewhere. SUBSIDIARY TAXA: A number of larger, but lesscommon taxa are more numerous on the reef tract thanin Florida Bay. There are new kinds of pelecypods(chamids and pectens) plus those large and spectaculargastropod shells so sought after by collectors, likeSiromhus and Cassis. Transennella cubaniana andChama florida (Text-fig. 15C, D), shown here, are list-ed in Table 6. If they appear in your samples they arehelpful, but they will not invariably be present. FAUNAE STRUCTURE: The fauna is rightskewed, with 80 () of its 189 taxa in the last1%. Comparisons Among the CaecumGroup BiofaciesTable 6 compares percentages of the Key and Dom-inant Taxa in the Cerithium (CE), Tricolia (TR.) and MoLLUSK Shells in Florida Bay: Shaw 23. -Most importani Reef Tract (RT) Biofacies. It illustrates again how bio-facies are separated by shifts in the proportions of asmall number of taxa, most of which are present inseveral biofacies. Grecian Rocks Biofacies This biofacies is based on only two samples col-lected at Grecian Rocks. It appears to be sufficientlydifferent from the Reef Tract Biofacies that borders iton the west to warrant separation, but with only twosamples available it is not yet sufficiently understoodfor detailed analysis and comparisons. DOMINANT TAXA: Eleven taxa make up the first50% of the assemblage: Caecum pulchellwn ()(Text-fig. 7C), Rissoinci fischeri () (), Barhaiia doiuiiigensis () (Text-fig. I6B).Tricolia affinis () (Text-fig. 14C), Rissoina hiy- Table 6.—Percentages of the most abundant taxa in the CaecaGroup of biofacies. CE = Cerithiiim Biofacies: RT = Reef TraBiofacies; TR = Tricolia Biofacies. TAXA CE TR RT Cerithium atratum
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