Keywords: Walcott Cambrian Geology and Paleontology II plate 28.jpg Plate 28 Middle Cambrian Crustaceans Opabinia Nathorstia and Naraoia 1 Opabinia regalis <small>Walcott</small> Opabinia regalis <small>Walcott 1912</small> 2 Nathorstia transitans <small>Walcott</small> Olenoides serratus <small> Rominger 1887 </small> 3 Naraoia compacta <small>Walcott</small> Naraoia compacta <small>Walcott 1912</small> 4 Naraoia compacta <small>Walcott</small> Naraoia compacta <small>Walcott 1912</small> 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 plates Opabinia fossils |