Tortoise Form

Goofy transforms into a tropical tortoise when he visits the Pride Lands with Sora and Donald. Like his alternate appearance in Atlantica, the only familiar part left of him is his head. The rest of body is merely that of a yellow tortoise.

Unlike his other forms, Goofy fights by spinning around and runs by doing the same.

Kingdom Hearts II
Two Weeks Vacation (1952)

''Captain of the Royal Knights. He's traveling the worlds with Sora and Donald in search of the King.''

Goofy's been transformed into a turtle in this world, and it seems to suit him just fine.

Trivia
Goofy's combo attacks are unavailable while visiting the Pride Lands.

The Tortoise and Turtle Forms were chosen because of Goofy's defensive abilities (the shells reference this). Both forms can also be called "turtles" depending on which kind of English you use, the "Tortoise Form" would then be called the "Land Turtle Form."