Just happened to be looking at Vokes & Vokes, 1983 "Distribution of
Shallow-Water Marine Mollusca , Yucatan Peninsula, Mexico.
They marked some species with an asterisk with the following explanation:
The species so indicated average less than 5 mm in size (although there are
exceptions in order not to separate members of the same genus). They are
segregated as "Micromollusca".....
Sounds good to me...
John Wolff
2640 Breezewood Dr.
Lancaster, PA 17601, U.S.A.