Echioceras raricostatum Jurassic ammonite fossil collected from the Lower Lias sediments of Charmouth, Dorset. Echioceras is a genus of ammonoid which existed during Lower Jurassic times. This specimen was derived from Lower Lias sediments; Lias being a Middle English term for Limestone but also used to describe the time period between the Rhaetian and Toarcian stages. This particular species has straight, distinct ribs which fade on the ventral margin; the ribs are particularly fine on the inner whorls. This specimen measures 4 cm in diameter and is supplied in a small plastic bag with an information label.