OTHER ECHINODERMS include extinct forms known as cystoids and blastoids. These animals fed by filtering small food particles from sea water. Some were stemmed forms that resemble crinoids (figures 1b, 3b), and some lacked a stem (figures 2, 4) and may have had a limited ability to move over the seafloor.
At least 7 species of cystoids and blastoids lived as dwellers in the Silurian reefs of Wisconsin. Four of these species are present in the diorama. The diorama also shows a few orange-colored starfish, another kind of echinoderm. Fossil starfish are known from Silurian rocks, but none have actually been found in the reef deposits.