Keywords: Walcott Cambrian Geology and Paleontology II text figure 10.jpg Sidneyia inexpectans Walcott � 3 Flattened dorsal shield with 4 pairs of cephalic appendages and jointed setiferous thoracic legs Middle Cambrian Burgess shale member of the Stephen formation National Museum of Natural History Paleobiology Collections 1912 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 Creator Charles Doolittle Walcott PD-old-80 Unidentified Arthropoda fossils Walcott Cambrian Geology and Paleontology II extracted images |