I recently acquired this Cystoid specimen called Paulicystis densus at a fossil show. It's from the Osgood shale (Silurian, Telychian to Sheinwoodian stage) and was collected in Napoleon, Indiana. I've collected at the same site before but I've only found Holocystites type cystoids. Paulicystis is a new genus that was named in 2011 by T.J. Frest and H.L. Stimple (honoring C.R.C. Paul) based on material donated by Don Bissett. The former two coauthored a paper but it never saw publication until 2011. Sadly both had passed before this occurred. The paper was finally completed in 2011 by C.R.C. Paul and published by the Paleontologial Research Institute in the Bulletins of American Paleontology, Number 380, March 2011. Click on the link to download a copy for yourself.
These next two pictures show the base of the Cystoid which shows that it had a very wide attachment to the seafloor.