Feeling her body, she felt something inside her back-gina.
She tried to see what it was, but unlike her other holes, this one had almost no internal vision. Michelle mused this being the case due to it needing to be more reinforced, to "chew" pieces onto bone, and sensitive eyes would not be useful for that.
So, with just her bottom hands, she framed her ass, and used fingers to pull apart the lips, using a tail to investigate.
It was dark inside, but as she positioned a tail in front of it, she could see what was inside; teeth, dozens of them, molars, hidden inside of the wall. What she had done with her snack was the equivalent of biting on a piece of food, and then breaking it off with her hands. With these, she could maul chew something inside.
And what better to test that with, than more rocks?
She was curious what muscle control she had down there, if there was no tongue. Though a strong quiver of rippling and churning muscles, looked promising to her at least.
She pulled her hands away, and let her back-gina close up. She then used her tails to start swallowing rocks, plumbing them into her back-gina canal.
The teeth demolished them, giving a satisfying "crunch" each time she tried chewing on it. She internally pouted a little, she she didn't wanna break them, she wanted to polish and sand them.
She kept picking up rocks, while she masturbated idly, her body bringing her to a river, settling on the bottom of it. She felt little fish getting trapped inbetween anemone folds on her hands, and her tails scour the riverbed for more stones. But she was only vaguely aware of that happening, as she focused on getting the churning and mauling right.
It wasn't about the rocks, or the masturbation, it was about her mastery over her body, if she could do that, it would be amazing.
She finally felt her instincts catch on, and adjust the chewing, and finally, in no time, she had her pouches full of smoothed rock.
Michelle sighed in satisfaction, sitting on the bottom of the riverbed, letting her tails and holes catch fish, while she ferried rocks one by one out of the pouches, and back on the river floor, watching the pretty color-bands exposed by the eroded surfaces.