The lowest 62 feet ( 19 m ) are predominantly shaley .
The lowest 62 feet ( 19 m ) include the Osmotherly , Avicula , Raisdale and Two - foot Seams , the best - developed being the Avicula Seam attaining c. 0.5 metre at Jet Wyke .
The lowest 62 feet ( 19 m ) are predominantly shaley and include the Osmotherly , Avicula , Raisdale and Two - foot Seams , the best - developed being the Avicula Seam attaining c. 0.5 metre at Jet Wyke .