1. E. Billings, 1860 .Description of some new species of fossils from the Lower and Middle Silurian rocks of Canada., Canadian Naturalist and Geologist, 5 :161 –177 .
2. J. Bridge, and P. E. Cloud .1947 .New gastropods and trilobites critical in the correlation of Lower Ordovician rocks., American Journal of Science, 245 :545 –559 .
3. D. Desbiens, T. E. Bolton, and A. D. McCracken .1996 .Fauna of the lower Beauharnois Formation (Beekmantown Group, Lower Ordovician), Grand Isle, Quebec., Canadian Journal of Earth Sciences, 33 :1132 –1153 .
4. R. Flower, 1968 .Some El Paso guide fossils., New Mexico Bureau of Mines and Mineral Resources Memoir, 22 :3 –19 .
5. C. F. Klappa, P. R. Opalinski, and N. P. James .1980 .Middle Ordovician Table Head Group of western Newfoundland; a revised stratigraphy., Canadian Journal of Earth Science, 17 :1007 –1019 .