Palaeacis obtusum Milne-Edwards & Haime

Osagean Series
Fern Glen Formation
Jefferson County, Missouri

Palaeacis obtusum Milne-Edwards & Haime 

 Palaeacis obtusum Milne-Edwards & Haime Palaeacis obtusum Milne-Edwards & Haime
Palaeacis obtusum Milne-Edwards & Haime

Originally described as a Sponge:
Sphenopoterium obtusum, M. and W. Oct. 1860
Geological Survey of Illinois Volume II Paleontology 1866

They are corals, not sponges. Granted, they are problematical
corals, but the current consensus is they are NOT sponges.
Alan Goldstein

Special thanks to:
Alan Goldstein for properly identifying this specimen.

The Fern Glen formation is noted for it's dark pink color.
When dry the fossils appear to be the same color as
the matrix. However, when wet (after a rain) they stand
out as white against the dark pink matrix. Much easier
and more fun to hunt the Fern Glen formation after a rain.

There is a "white" Fern Glen also. I really don't know the
reason for the two colors.

Fern Glen Formation

Mississippian Fossils of Missouri