"Much of the massive limestone formation is composed of sand-sized particles of calcium carbonate, fragments of crinoid plates, and shells broken by the waves. Such a sedimentary rock qualifies for the name sandstone because it is composed of particles of sand size cemented together; because the term sandstone is commonly understood to refer to a quartz-rich rock, however, these limestone sandstones are better called calcarenites. The Madison sea must have been shallow, and the waves and currents strong, to break the shells and plates of the animals when they died. The sorting of the calcite grains and the cross-bedding that is common in this formation are additional evidence of waves and currents at work. Even in Mississippian rocks, where whole crinoids are rare fossils, and as a result, it is easy to underestimate the population of these animals during the Paleozoic era. Crinoidal limestones, such as the Mission Canyon-Livingstone unit, provide an estimate, even though it be of necessity a rough one, of their abundance in the clear shallow seas they loved. In the Canadian Rockies the Livingstone limestone was deposited to a thickness of 2,000 feet on the margin of the Cordilleran geosyncline, but it thins rapidly eastward to a thickness of about 1,000 feet in the Front Ranges and to about 500 feet in the Williston Basin. Even though its crinoidal content decreases eastward, it may be calculated to represent at least 10,000 cubic miles of broken crinoid plates. How many millions, billions, trillions of crinoids would be required to provide such a deposit? The number staggers the imagination."
Thomas H. Clark and Colin W. Stearn, The Geological Evolution of North America, (New York: The Ronald Press, 1960), p. 86-88