Reference for Zevachim 115:4

וכי תימא הכי נמי והא את הוא דאמרת משמיה דרבי יוחנן מודי רבי יוסי בר"י שאם שחטן כנגדן בקרקע פסולה

Hence he informs us [that it is not so]. Said R'Zera to R'Assi If so, will you indeed say that R'Jose son of R'Judah holds that [the altar] is half in the north and half in south?<span class="x" onmousemove="('comment',' R. Zera assumed that R. Assi's statement was inferred from the Mishnah: since R. Jose rules that if it is slaughtered anywhere on the top of the altar, it is as though it is slaughtered in the north, it follows that the whole of the altar is in the north. But if this inference is correct, a simil deduction can be made with respect to R. Jose b. R. Judah.');">⁴</span>

Jastrow