1. J. R M. Bergenhayn, 1960 .Cambrian and Ordovician loricates from North America., Journal of Paleontology, 34:168 –178 .
2. C. P. Berkey, 1898 .Geology of the St. Croix Dalles. Pt. 3., American Geologist, 21:270 –294 .
3. J. S. Cullison, 1944 .The Stratigraphy of some Lower Ordovician formations of the Ozark Uplift., Univ. of Missouri School of Mines and Metallurgy Bulletin Technical Series, 15:1 –112 .
4. W. B. Howe, 1966 .Digitate algal stromatolite structures from the Cambrian and Ordovician of Missouri., Journal of Paleontology, 40:64 –77 .
5. A New Living Deep-Sea Mollusc of the Cambro-Devonian Class Monoplacophora