Ligament external, seated on narrow nymph; resilifer absent

Orginally proposed as a subgenus of Solemya, this is a cosmopolitan deep-water genus known from the Permian and perhaps the middle Devonian. The name is derived from the Greek a (=without), and charax, a pointed stake. The gender is feminine. The only species thus far studied, Acharax eremita Kuznetsov and Schileyko, 1984, lacks a digestive tract.