An old Anishinaabe Legend about how the turtle gets its shell goes something like this. I've heard and read it different ways, but the idea is always the same.
Nanabozho (a spirit in common throughout Anishinaabe mythology) accidentally hurts Mishekae (turtle), who's sunning by a lake. During the time the legend takes place the Mishekae was not known as we know turtles today, she had no shell and was all soft skin and bone.
Embarrassed and apologetic for his clumsiness, Nanabozho returns with a gift of protection. He takes two large shell from the lake shore, placing one on top of the other and sandwiches Mishekae in between.
"You will never be injured again. Whenever danger threatens, you can pull your legs and head into the shell for protection."
Nanabozho then describe how the shell Mishekae wears symbolizes Mother Earth. The carapace resembling the hills and mountains. There's a reference on how the shell is divided into separate segments each uniquely different yet all connected. All as one.
The legend has Nanabozho revealing what the turtle also symbolizes to the Anishnabek.
A turtle has four legs representing the cardinal directions, North, South, East and West. The tail represents all the experiences, history, the lands that have been traveled. While the head, points in the direction to follow, the future.
Additionally, because of Nanabozho's gift, the turtle is at home both on land and in the water.
A great site for other Native Americas legends can be found here.
http://www.firstpeople.us/FP-Html-Legends/Legends-AB.html The site currently has over 1400 Native American stories and they are continuously adding to the library.
If you specifically looking for the legend I described herein, click to this link.