Masoretic Perversion of Text

Reading Abraham's account with God in Gen 15, Bullinger notes (Companion Bible) Jeremiah 34:18 "when they cut the calf in twain, and passed between the parts thereof" yet the LXX doesn't have this at all. Interestingly, the LXX has more chapters and text than the masoretic text of Jeremiah and so this same citation is actually 41:18 and it merely only states "which they made before me, the calf which they prepared to sacrifice with it" and nothing about passing through it and cutting it in half. Here we have a clear anti astrological perversion by the masoretic text.