Hysteroconcha
Morphology:
Species of the genus Hysteroconcha are defined by the presence of one of more row of spines, often coinciding with strong concentric riblets, at the confluence of the posterior and central areas of the flank. The spines may be strong and prominent, as in H. lupanaria, or weak and/or broken, as in the species H. rosea. The lunule is typically small, not extending more than half of the anterior dorsal margin.