Dear Atsushi,
My understanding is that the shell of the type species of each genus are very similar. However Berthelinia is based on a fossil species while Tamanovalva is based on a living animal. We will never know whether the similarity in shell shape is based on a close phylogenetic relationship or on chance. For example, there are many cephalaspidean bubble shells which are impossible to place in families simply on the shape of the shell so I think it is unsafe to use a fossil name for a living animal. Kathe Jensen follows Baba (1961) in using the fossil Berthelinia for the living species and considers in fact that there are only two valid genera in the family Juliidae, Julia and Berthelinia. Baba and Jensen both consider Edenttellina and Midorigai are either synonyms, or at the most, subgenera of Berthelinia. I have continued to use Edenttellina and Midorigai for Australian species because that has been the current practice here in Australia, and there are considered to be some anatomical differences.

Clearly our inability to ever convincingly show that the fossil Berthelinia elegans Crosse, 1875 [which is in fact based on a 0.5mm immature left valve] is congeneric with living Tamanovalva limax Kawaguti & Baba, 1959 is a problem. The problem becomes more complicated if we decide to keep the fossil and living species separate, because Edentellina is an earlier name for living species than Tamanovalva. We would therfore have to decide whether Tamanovalva and Edentellina were distinct genera or not before we could attempt to stabilise the names of the living bivalved gastropods of the world.

Any thoughts very welcome,
Best wishes,
Bill Rudman