Animal with a prominent head and muzzle, the males with an intromittant organ at the base of the right tentacle ; a single lamellose asymmetrical gill between the under surface of the mantle and the upper surface of the body from a point above and behind the head, extending around toward the right, and even backward on the right side ; attached only at its base. Eyes wanting in the known species. Anus anterior, opening in a papilla above and behind the head. Mantle-margin and sides of foot plain, without epipodial papilla? or processes, but they are sometimes present behind.