Tortoise having shell on their body surface, so why they can not be counted as in phylum mollusca?

Tortoise having shell on their body surface, so why they can not be co

1.	Tortoise having shell on their body surface, so why they can not be counted as in phylum mollusca?
Answer» There are\xa0three layers\xa0in the\xa0shell\xa0of P. fucata: the outer periostracum\xa0layer, the middle prismatic\xa0layer\xa0and the inner nacreous\xa0layer.\xa0Mollusk shells\xa0are\xa0made\xa0of a chalky material called calcium carbonate. The\xa0shell\xa0has three layers for extra strength: a tough outer layer, a chalky middle layer, and a shiny inner layer, next to the animal\'s skin. The shiny layer in some bivalve\xa0mollusks\xa0is known as mother-of-pearl.