Keywords: Opabinia regalis - Walcott Cambrian Geology and Paleontology II plate 28 .jpg Opabinia regalis Walcott 1912 Dorsal view of a male specimen flattened in the shale showing fp frontal appendage e eye ths thoracic somites i intestine ab abdominal segment U S National Museum Catalogue No 57684 Charles D Walcott Middle Cambrian Branchiopoda Malacostraca Trilobita and Merostomata Smithsonian Miscellaneous Collections Volume 57 Number 6 Publication 2051 City of Washington Published by the Smithsonian Institution March 13 1912 1912 Creator Charles Doolittle Walcott PD-old-80 Walcott Cambrian Geology and Paleontology II plate 28 jpg Walcott Cambrian Geology and Paleontology II plates Opabinia fossils |