There is also a colonial coral . Note the second stem showing the less often preserved arms. There is also a crinoid stem embedded in rock. Until recently classified as sponges, recepticulites are now thought to be fossils of algae of the division Chlorophyta. They lived from the Ordovician to the Permian.
Whole specimens are globular to platter shaped.
Three different species of sponge are displayed. First is the cup-shaped Astraeospongia meniscus . Note the star-shaped spicules apparent in this specimen. These important Silurian and Devonian period reef-building organisms are thought to be sponges, though they were previously classified as corals. The fossils are encrusting, cylindrical, or massive.