Their shell size and shape are different between populations.

The shell size varies between 20mm and 50 mm.

The shell size is between 50mm and 85 mm.

Additional configurations up to 24 pins are also offered in the same shell size.

With is shell size up to 67 mm was at least twice larger than any recent known living monoplacophoran species.

The adult shell size of this species is about 60 to 90 mm.

The shell size varies between 30 and 52 mm.

Maturity is reached at half maximum shell size after 1 year.

The shell size is between 10 and 18 mm.

The shell size varies between 33mm and 80 mm.