Shell length (SL) is the horizontal distance from the anterior end to the posterior end of the shell.

Shell height (SH) is the vertical distance from the umbo to the ventral margins of the shell.

Shell breadth (SB) is the widest distance when the two valves are closed.

Shell length (SL) is the vertical distance from the apex to the anterior canal end of the shell.

Shell width (SW) is the widest distance of the shell when the aperture view face to you