The Conulata, also known as conulariids, form a poorly understood clade of extinct scyphozoan cnidarians. The conulariids are preserved as shell-like structures made up of rows of calcium phosphate rods, resembling an ice-cream cone with fourfold symmetry, usually four prominently-grooved corners. New rods were added as the organism grew in length; the rod-based growth falsely gives the fossils a segmented appearance. Exceptional soft-part preservation has revealed that soft tentacles protruded from the wider end of the cone, and a holdfast from the pointed end attached the organisms to hard substrate. The prevailing reconstruction of the organism has it look superficially like a sea anemone sitting inside an angular, hard cone held perpendicular to the substrate. Setting aside for the moment the Precambrian vendoconulariids, which may or may not be conulariids at all, the Conulata fossil record begins with undoubted specimens in the Upper Cambrian (Hughes et al., 2000) and extends without significant break through numerous major mass extinctions. The Conulariids finally disappear from the rock record during the Lower Triassic stage of the Triassic Period (~245 million years ago). In North America, conulariids are generally least uncommon in rocks of Ordovician and Carboniferous age. Conulariids apparently lived only in normal-marine waters, such as the oceans and inland seas. Fossils are commonly found in rocks representing offshore, even anoxic, marine bottom environments. This has led some scientists to infer that these animals may have drifted planktonically for some or all of their lives, ultimately being buried in the anoxic sediments beneath the oxic waters in which they lived. However, basic functional considerations (such as the great weight of the shell) make such interpretations difficult to maintain.
Source: http://en.wikipedia.org/wiki/Conulariida and http://www.geol.umd.edu/~jmerck/bsci392/lecture22/lecture22.html
An artistic reconstruction of conulariid