Young individuals have their valves covered with a squamous epidermis arranged radially (« squamis suberectis, numerosis, aequidistantibus » in Fischer); on their side, the adults are often devoid of this periostracum. Above, the species plate IX, fig.1 in the vol. XV of the Journal de Conchyliologie.

« According to a communication from Mr. Mac-Andrew, the Kellia Mac-Andrewi reaches larger dimensions than those which I indicated and which I took from examples from the rich collection of Mr. Petit de la Saussaye. Old individuals are generally devoid of epidermis and therefore lack squamous rays. » – P. Fischer: Ibid. Above, a specimen from the Camargue sedimentary area, S. France: at low tide, Saintes-Maries-de-la-Mer, Bouches-du-Rhône, Provence. 11,3mm. The periostracum of this adult lost its squamae. Original pictures provided by A. Nappo (IT) – (CC BY-NC-SA).