The carapace of this species can reach more than 40cm (16in) in length, but the average length ranges from 15 to 20cm (6 to 8in).[6] The females of the species are usually larger than the males. They typically live between 20 and 30 years, although some individuals have lived for more than 40 years.[7] Their life expectancy is shorter when they are kept in captivity.[8] The quality of their living environment has a strong influence on their lifespans and well being.