Though tortoise lives on land as well as in water , it cannot be included in class - Amphibia.

Explanation

(i)The animals which not only live in water but also on land and respire in both climatic conditions are called Amphibians.
(ii)Tortoise respires through lungs but does not have a structure to respire in water.
(iii)Also, tortoise lays eggs with hard shells which is a characteristic of reptiles.
(iv)Tortoise has a neck, whereas neck is absent in
amphibian. Therefore, tortoise is not an amphibian.