In many taxa, there is no sculpture on the shell surface at all, apart from the presence of fine growth lines.

The shell surface is generally smooth, sometimes with a spiral and/ or axial sculpture.

The periostracum of the shell surface has no hairs.

Animal mantle smooth, at least partially extending over external shell surface.

A very faint spiral striation is visible all over the adult shell surface.

The outer shell surface is shiny and reddish in color.

The shell surface is sculptured with rather coarse lines.

Many species have colorful patterning on the shell surface.

The mantle appears not to extend completely over the external shell surface.

Mantle smooth, at least partially extending over external shell surface.