Here is a scan of a modern Mushroom Coral (Scleractinia: Fungiidae).
The specimen looses much of its fine detail in this scan, but the general platy texture is survives the digitization process.
Scanned by Artur Pacyga in Dr. Franek Hasiuk's GeoFabLab (Department of Geological and Atmospheric Sciences, Iowa State University) from an unmarked specimen.
Scan Specifications: Scanned with the MakerBot Digitizer Desktop 3D Scanner set on "Medium".
Here's a journal article on Mushroom Corals: http://www.auburn.edu/cosam/faculty/biology/chadwick/website/Publications_files/Goffredo%20and%20Chadwick-Furman%202000.pdf