| The circular to oval specimens are cross-sections of an extinct variety of calcareous sponge, called archaeocyathids, from the Lower Cambrian Poleta Formation, Esmeralda County, Nevada. |
| The circular to oval specimens are cross-sections of an extinct variety of calcareous sponge, called archaeocyathids, from the Lower Cambrian Poleta Formation, Esmeralda County, Nevada. |