Cerata on Coryphella gracilis are narrowed at base so often elliptical (1), and less slender and flexible than cerata on C. v. rufibranchialis. Arise from more pronounced notal ridge containing digestive gland (2). Narrow subterminal opaque white ring on cerata (3). Opaque white dorsal line on tail is sometimes fragmentary (4). Matures at small size so white ovotestes visible(5) when 8 mm long, at which size ovotestes are usually missing in juvenile Coryphella verrucosa.
Left: Length 8.5 mm. Menai Strait, Wales. April 2011. Right: olive cerata. Lewis, Scotland. April 2018. Leg. Simon Taylor.