(Mishnah): One who buys water, salt, produce connected to the ground or produce that cannot arrive in Yerushalayim (before rotting); it does not acquire the Kedushah of Ma'aser Sheni.

If one inadvertently used Ma'aser Sheni money to buy produce outside Yerushalayim, the money must be returned. If done intentionally, he must take that produce and eat it in Yerushalayim. And if there is no Beis HaMikdash, it must be left to rot.

If one inadvertently used Ma'aser Sheni money to buy an animal outside of Yerushalayim, the money must be returned. If done intentionally, he must take it to Yerushalayim and eat it there. And if there is no Beis HaMikdash, he must wait for it to die and then bury it together with its skin.

One may not buy slaves, fields or non-Kosher animals with Ma'aser Sheni money. If he did, he must consume an equivalent amount of food as Ma'aser Sheni in Yerushalayim.

One may not bring from Ma'aser Sheni money bird offerings of a Zav, a Zava or a woman after childbirth. If he did, he must consume an equivalent amount of food as Ma'aser Sheni.

The general rule is that whatever is bought with Ma'aser Sheni money that cannot be eaten, drank, or rubbed; he must consume an equivalent amount of food as Ma'aser Sheni.

(Gemara) (Baraisa): If a person bought a non-Kosher animal with Ma'aser Sheni money, whether it was done inadvertently or intentionally, the money must be returned.

Question (Mishnah in Maseches Sheviis 8:8): 'One may not buy slaves, fields or a non-Kosher animal with Sheviis money and if he did, he must consume an equivalent amount of Sheviis money.' But here you said that the money must be returned?

Answer (R. Yona): The way to answer this contradiction is a dispute between R. Chiya bar Rav Yosef and Shmuel - one said that when the Mishnah taught that one must consume the equivalent amount, it was referring to when it was acquired through a sale. And when the Baraisa taught that the money must be returned, it was referring to when he was redeeming the Kedushah of Ma'aser Sheni from the money onto a non-Kosher animal.

And the other opinion said that the Baraisa refers to when the seller is still here (so the money must be returned) and the Mishnah refers to when he is no longer here.

However, I didn't know which Amora had said each explanation. But from that which R. Yosi cited from Shmuel about the Mishnah (in Sheviis) that the acquisition stands (and it certainly refers to when the seller was still there); this shows that it was Shmuel that had said that the Mishnah was a sale and the Baraisa was a redemption.