The small-scaled reefs are generally domical or lenticular in shape, ranging in height from tens of centimeters to several meters, and in width from less than a meter to more than 10 m. They are chiefly built by benthic microbes, lithistid sponges, the quasi-sponge fossils Calathium as well as bryozoans and are usually surrounded by skeletal/intraclastic grainstones and packstones. Skeletal fragments of ostracods, trilobites, gastropods, brachiopods, nautiloids, and echinoderms are found within the reefs and surrounding sediments. Three reefal types are recognized.