Notes on the genus Anadema H. and A. Adams, 1854 (Gastropoda: Colloniidae)

Shell morphology and characters of the living animal of the poorly known, Atlantic Moroccan species Anadema macandrewii (Mörch, 1864) are described and illustrated, based on beach collected specimens and a single live-collected specimen. The genus is monotypic and is assigned to the Colloniidae rather than Turbinidae because of the domeshaped profile of the shell, open umbilicus, symmetrical tooth rows of the radula, lack of cephalic lappets, and the non-bicarinate juvenile shell. Within the Colloniidae, it unusual for its relatively large mature shell, juvenile shell with a keeled profile, and the lack of the secondary flap above the rachidian tooth. The species is regarded as sexually dimorphic, with the female shell having a raised periumbilical rim comparable to that of other trochoideans modified for brooding by means of an enlarged umbilical cavity.