>I notice that superfamily names of pulmonate shells have been written
>variously with the "-idea" suffix or with the "-acea" suffix, depending on
>source. Superfamily names in Abbott's Seashells Compendium always end in
>"-acea,"  though Abbott used the "-idea" ending in his earlier land shell
>book. Is there now a preferred ending for specifically the superfamily level
>(not suborder)? Or, am I just seeing out-of-date usage in some cases?
>
>-Burton

Strictly speaking malacologists have dragged their heels on this one.
Most workers on other phyla have been using -oidea (not -idea) for a
long time, though some brachiopod workers also still use -acea.

Note that Rissoidae belong to Rissooidea; Rissoidea is incorrect.

>-oidea is now the official ending for superfamilies.  Before
>the ICZN made this declaration, -acea was widely used by
>molluscan workers.  This results in some potential
>confusion, as a few genera also end in -oidea.  Thus,
>Nuculoidea is a Paleozoic genus in the superfamily
>Nuculoidea.

There are further problems at higher taxonomic levels too. Order
Nautiloidea, for instance, as well as the superfamily of the same
name. So "nautiloid" can have 2 meanings: Member of the superfamily
or member of the order. I believe there are NO rules for taxonomic
names above superfamilial names. That IS stupid.