Eurypterid Specimen Length= 50mm Origin= Fiddler's Green Dolostone, New York Age= Silurian   SEM Images Images showing fossil preserved in carbonate, with some carbon.   Silicate Concretion Specimen Length= 55mm Origin=Conasauga Formation, NW Georgia Age= Cambrian   SEM Images Images showing details of concretion made of quartz.   Blob Specimen Length= 87mm Origin=Fiddler's Green Dolostone, New York Age= Silurian   SEM Images Images showing possible microbial mats preserved by carbon and magnesium carbonate.   Ripples Specimen Length= 58mm Origin= Kope Formation, N Kentucky Age= Ordovician   SEM Images Images showing sedimentary structures that were probably stabilized by microbes.   Trace Fossils Specimen Length= 62mm Origin= Kope Formation, N Kentucky Age= Ordovician   SEM Images Images showing aggregated clay minerals forming walls of traces in sediments.   Cephalopod Specimen Length= 36mm Origin= Cincinnati Area, Ohio Age= Ordovician   SEM Images Images showing calcite crystals and probable bacterial cells (tiny, round structures) coating shell material.   Blob Specimen Length= 44mm Origin= Fiddler's Green Dolostone, New York Age= Silurian   SEM Images Images showing algal mat preserved as carbon; an algal flake is shown in one SEM photo.   Ooids Specimen Length= 54mm Origin= Great Salt Lake, Saltair, Utah Age= Holocene (modern)   SEM Images Images showing ooid spheres (lower magnification) and tiny, round bacterial cells associated with the ooids (higher magnification).   Microbial Limestone encrusting Volcanic Glass Specimen Length= 29mm Origin= Carapace Nunatak, Antarctica Age= Jurassic   SEM Images Images showing limestone (calcium carbonate) with dark, twisted, strandlike bodies that probably represent archaebacteria.   Insect Specimen Length= 51mm Origin= Green River Formation, W Colorado Age= Eocene   SEM Images Images showing insect body preserved as carbon in clay matrix.