Those in McDonald I have not seen, but they are reported to be very extensive and probably are situated in the Encrinital Limestone.
"Cave Regions of the Ozarks and Black Hills" by Luella Agnes Owen
Encrinites, figure of, 264.
"A Manual of Elementary Geology" by Charles Lyell
Some of them, as the encrinites or sea-lilies, are permanently fixed by a stalk when adult.
"The New Gresham Encyclopedia" by Various
In both of these the stalk bears, as in Encrinites, a calyx or head, which is comparable, with the body of the free Echinoderms.
"Stories of the Universe: Animal Life" by B. Lindsay