The Upper Conbeari Bed marks the top of the Sinemurian whilst the overlying double nodule band marks the base of the Carixian. Deroceras is more characteristic of the Jamesoni Zone at the base of the Carixian than the Raricostatum Zone of the Sinemurian. However there is no doubt of the position of the specimen as 6.0ft. below the double nodule band and 1.0ft. above the Conybeari Bed, as being on the boundary of the Jamesoni and Raricostatum Zones.