there is no complete identification guide available in the literature . keep in mind that many species described, might be different forms of a single species. many descriptions of species are based solely on only a few, empty shells. colour, banding and shell surface ( rough, smooth etc.) are no good...
silicified in a chalcedony base. turritella are spiral marine gastropods having elongated, spiral shells composed of many whorls. similarly, coral , petrified wood and other organic remains or porous rocks can also become agatized. agatized coral is often referred to as petoskey agate or stone. montana...