Charles Doolittle Walcott (1886). Second contribution to the studies on the Cambrian faunas of North America. Vol. 30 of Geological Survey bulletin. Govt. Print. Off. pp. 1–369.
Charles Doolittle Walcott (1886). Second contribution to the studies on the Cambrian faunas of North America. Vol. 30 of Geological Survey bulletin. Govt. Print. Off. pp. 1–369.