Shell

"Old hunter recipe," Butch said.  "Roast turtle.  Ingredients: one turtle, one campfire.  Put the turtle on the fire; when the shell cracks, it's done."  He stirred the embers and shoved a few more sticks into the wavering red heart of the flame.  "You got to crack the shell to get at the meat anyway, right?" 

The scaly feet waved in the smoke.

"Is the shell there to keep us out?" Caleb wondered.  "Or is it to keep something else in?"

There was a sudden, sharp crack, like a gunshot.  The flames roared as the wind came down.  Then silence.

Tortoiseshell

Taku prodded the brownish lump. The turtle retracted its head further, but did not otherwise move. "Remind you of anyone?" he asked.

"No," said the Wisest Stone.

"Don't be difficult."

"The turtle misunderstands the purpose," the Wisest Stone went on, settling deeper into his mossy bed. "He builds the hard shell, but then he lives within, letting the world break against it."

"Like a rock in a stream, yes?" Taku plucked a green leaf and placed it in front of the turtle, who remained stubbornly hidden.

"To be rock is to be the shell, not to be behind the shell."