Walcott, C.D., 1912, Cambrian Brachiopoda: U.S. Geological Survey Monograph 51, 2 vols., Part 1, Text, 872 p.; Part 2, Plates, 363 p.
Walcott, C.D.
U.S. Geological Survey Monograph 51, 2 vols., Part 1, Text, 872 p.; Part 2, Plates, 363 p.
Paleontology, Invertebrate, Cambrian,
